4. Nervous system ppt..ppt which important
MulugetaAbeneh1
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Jun 25, 2024
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About This Presentation
anatomy
Slide Content
Nervous System
Locational and functional division of the Nervous system
I. Structural division
A. Central nervous system (CNS):
Command center of nervous system that interprets and
processes nervous information.
Consist of: Brain and spinal cord.
B. Peripheral nervous system (PNS):
Projects information to and receives information from CNS,
mediates some reflexes. Such as Nerves and ganglia.
II. Functional divisions
Sensory (Afferent) division:
-Somatic sensory
-Visceral sensory.
Some CNS and PNS components (including sensory
neurons).
Consists of all axons that transmits a nerve impulse form a
peripheral structure to the CNS; includes pain, touch,
temperature, and pressure; input information.
I. Structural division
A. Central nervous system (CNS):
Command center of nervous system that interprets and
processes nervous information.
Consist of: Brain and spinal cord.
B. Peripheral nervous system (PNS):
Projects information to and receives information from CNS,
mediates some reflexes. Such as Nerves and ganglia.
II. Functional divisions
Sensory (Afferent) division:
-Somatic sensory
-Visceral sensory.
Some CNS and PNS components (including sensory
neurons).
Consists of all axons that transmits a nerve impulse form a
peripheral structure to the CNS; includes pain, touch,
temperature, and pressure; input information.
Transmit input from skin, fascia, joints, and skeletal muscle.
Transmit input from viscera
Motor (efferent) division:
-Somatic motor (somatic nervous system; SNS)
-Autonomic motor (Autonomic nervous system (ANS)
Some CNS and PNS components (including motor neurons).
Consist of all axons that transmit a nerve impulse form the CNS
to a muscle or gland, “out put” information.
Voluntary control of skeletal muscle, involuntary control of
smooth muscle, cardiac muscle and glands.
Cytology of nervous tissue
Two distinct cell types forms nervous tissues
Neuron: which are excitable cells that initiate and transmit
nerve impulses.
Neuroglia: which are non excitable cells that support and
protect the neurons.
Transmit input from viscera
Motor (efferent) division:
-Somatic motor (somatic nervous system; SNS)
-Autonomic motor (Autonomic nervous system (ANS)
Some CNS and PNS components (including motor neurons).
Consist of all axons that transmit a nerve impulse form the CNS
to a muscle or gland, “out put” information.
Voluntary control of skeletal muscle, involuntary control of
smooth muscle, cardiac muscle and glands.
Cytology of nervous tissue
Two distinct cell types forms nervous tissues
Neuron: which are excitable cells that initiate and transmit
nerve impulses.
Neuroglia: which are non excitable cells that support and
protect the neurons.
•Nervous tissue
Found in the brain, spinal cord, and nerves
•It is responsible for coordinating, controlling and integrating
many body activities.
•It stimulates circulation, respiration muscle contraction,
creates an awareness of the environment, and plays a major
role in emotions, memory, and reasoning.
Basic function of nervous system
1.Sensation
•Monitors changes/events occurring in and outside the body.
Such changes are known asstimuliand the cells that
monitor them are receptors.
2.Integration
•The parallel processing and interpretation of sensory
information to determine the appropriate response
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Found in the brain, spinal cord, and nerves
•It is responsible for coordinating, controlling and integrating
many body activities.
•It stimulates circulation, respiration muscle contraction,
creates an awareness of the environment, and plays a major
role in emotions, memory, and reasoning.
Basic function of nervous system
1.Sensation
•Monitors changes/events occurring in and outside the body.
Such changes are known asstimuliand the cells that
monitor them are receptors.
2.Integration
•The parallel processing and interpretation of sensory
information to determine the appropriate response
6
3.Reaction
•Motor output.
–The activation of muscles or glands (typically via the
release of neurotransmitters(NTs))
Nerve Cells
•Two distinct cell typesform nervous tissue.
–Neurons, which are excitable cells that initiate and transmit
nerve impulses
–Glial cells (neurogelia), which are no excitable cells that
support and protect the neurons.
Special Characteristics of Neurons
–Longevity –can live and function for a lifetime
–Do not divide (amitotic)–fetal neurons lose their ability to
undergo mitosis; neural stem cells are an exception
–High metabolic rate –require abundant oxygen and glucose
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•Motor output.
–The activation of muscles or glands (typically via the
release of neurotransmitters(NTs))
Nerve Cells
•Two distinct cell typesform nervous tissue.
–Neurons, which are excitable cells that initiate and transmit
nerve impulses
–Glial cells (neurogelia), which are no excitable cells that
support and protect the neurons.
Special Characteristics of Neurons
–Longevity –can live and function for a lifetime
–Do not divide (amitotic)–fetal neurons lose their ability to
undergo mitosis; neural stem cells are an exception
–High metabolic rate –require abundant oxygen and glucose
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Neuron Structure
•Neurons come in all shapes and sizes, but all neurons share
certain basic structural features.
•A typical neuron has a cell body, dendrites,and axons.
a. Cell Body, Aka Soma or Perikaryon
•Contains usual organelles plus other structures
–Nissl bodies = chromatophilic substance = rough E.R:
primary site of protein synthesis
–Cytoskeleton of neurofilamentsand neurotubules
–No centrioles (hence its amitotic nature)
•control centerand is responsible for receiving, integrating, and
sending nerve impulses.
•Most neuronal cell bodies
–Located within CNS
–Ganglia-clusters of cell bodies that lie along nerves in PNS
•Tapers to form axon hillock
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•Neurons come in all shapes and sizes, but all neurons share
certain basic structural features.
•A typical neuron has a cell body, dendrites,and axons.
a. Cell Body, Aka Soma or Perikaryon
•Contains usual organelles plus other structures
–Nissl bodies = chromatophilic substance = rough E.R:
primary site of protein synthesis
–Cytoskeleton of neurofilamentsand neurotubules
–No centrioles (hence its amitotic nature)
•control centerand is responsible for receiving, integrating, and
sending nerve impulses.
•Most neuronal cell bodies
–Located within CNS
–Ganglia-clusters of cell bodies that lie along nerves in PNS
•Tapers to form axon hillock
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b. Dendritestend to be shorter, smaller processes that branch off
the cell body.
•Some neurons have only one dendrite, while others have many.
•Dendrites conduct nerve impulses towardthe cell body; they
receive input and then transfer it to the cell body for processing.
•The more dendrites a neuron has, the more nerve impulses that
neuron can receive from other cells.
c. Axon-larger, typically longernerve cell process emerging
from the cell body is the axon, sometimes called a nerve fiber.
•Most neurons have only one axon.
•The axon transmits a nerve impulse awayfrom the cell body
toward another cell.
•Axon hillock: Initial segment
•Multiple branches at end of axon, terminal branches
(telodendria)
–End in knobs called axon terminals it contain vesicles filled
with neuro-transmitter (NT)
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the cell body.
•Some neurons have only one dendrite, while others have many.
•Dendrites conduct nerve impulses towardthe cell body; they
receive input and then transfer it to the cell body for processing.
•The more dendrites a neuron has, the more nerve impulses that
neuron can receive from other cells.
c. Axon-larger, typically longernerve cell process emerging
from the cell body is the axon, sometimes called a nerve fiber.
•Most neurons have only one axon.
•The axon transmits a nerve impulse awayfrom the cell body
toward another cell.
•Axon hillock: Initial segment
•Multiple branches at end of axon, terminal branches
(telodendria)
–End in knobs called axon terminals it contain vesicles filled
with neuro-transmitter (NT)
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Neuron classification: Neurons vary widely in morphology and
location.
They can be classified according to either their structure or
their function
Structural classification: Uniplar neurons Bipolar neurons
Multipolar neurons
Neurons are classified according to the number of neuron
processes emerging directory from the cell body, as unipolar,
bipolar, or multipolar
Uniplar neurons: Have a single, short neuron process that
emerges from the cell body and branches like a T.
These neurons are also called pseudo unipolar because they
start out as bipolar neurons during development, but their two
processes fuse in to a single process. most sensory neurons
are unipolar.
Bipolar neurons: have two neuron processes that extend from
the cell body one axon and one dendrite.
location.
They can be classified according to either their structure or
their function
Structural classification: Uniplar neurons Bipolar neurons
Multipolar neurons
Neurons are classified according to the number of neuron
processes emerging directory from the cell body, as unipolar,
bipolar, or multipolar
Uniplar neurons: Have a single, short neuron process that
emerges from the cell body and branches like a T.
These neurons are also called pseudo unipolar because they
start out as bipolar neurons during development, but their two
processes fuse in to a single process. most sensory neurons
are unipolar.
Bipolar neurons: have two neuron processes that extend from
the cell body one axon and one dendrite.
These neurons are relatively uncommon in humans and
primarily limited to some of the special senses (taste, vision,
hearing, balance, smelling).
e.g Bipolar neurons are located in the olfactory epithelium of the
nose & in the retina of the eye
Multipolar neurons:Are the most common type of neuron.
Multiple neuron processes many dendrites and a single axon
extending from the cell body.
E.g multipolar neurons include motor neurons that innervate
muscle and glands.
primarily limited to some of the special senses (taste, vision,
hearing, balance, smelling).
e.g Bipolar neurons are located in the olfactory epithelium of the
nose & in the retina of the eye
Multipolar neurons:Are the most common type of neuron.
Multiple neuron processes many dendrites and a single axon
extending from the cell body.
E.g multipolar neurons include motor neurons that innervate
muscle and glands.
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Supporting Cells (Neuroglial Cells) in the CNS
usually only refers to supporting cells in the CNS but occur in
PNS
•Glial cells have branching processes and a central cell body
•Make up half the mass of the brain
•Can divide throughout life
•May divide abnormally -glioma-brain cancer
•Do not transmit nerve impulses.
•Smaller than neurons, support for neurons, intertwine with
neurons,
•line certain structures in brain and spinal cord, bind nervous
system to blood vessels,
•insulate and cover neuron axons with myelin, increase speed of
transmission, phagocytic.
•Include astrocytes, oligodendrocytes, microglia, ependymal
cells, Schwann cells (neurolemmocytes), and satellite cells.
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usually only refers to supporting cells in the CNS but occur in
PNS
•Glial cells have branching processes and a central cell body
•Make up half the mass of the brain
•Can divide throughout life
•May divide abnormally -glioma-brain cancer
•Do not transmit nerve impulses.
•Smaller than neurons, support for neurons, intertwine with
neurons,
•line certain structures in brain and spinal cord, bind nervous
system to blood vessels,
•insulate and cover neuron axons with myelin, increase speed of
transmission, phagocytic.
•Include astrocytes, oligodendrocytes, microglia, ependymal
cells, Schwann cells (neurolemmocytes), and satellite cells.
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Neuroglia of CNS:
Largest and most numerous
Functions include:
1. Astrocytes
1.Form the blood-brain barrier
–Take up and release ions (Na, K) to control the
environment around neurons
–Regulate what substances reach the CNS from the blood
2. Recapture and recycle neurotransmitters.
3. Involved with synapse formation in developing neural tissue
4. Aid in repair of damaged neural tissue
5. Produce molecules necessary for neural growth.
2. Ependymal Cells
Line brain ventricles and spinal cord central canal.
–Specialized versions of ependymal form choroid plexuses.
Choroid plexus-secrete cerebrospinal fluid. Cilia help move fluid
through the cavities of the brain.
Neuroglia of CNS:
Largest and most numerous
Functions include:
1. Astrocytes
1.Form the blood-brain barrier
–Take up and release ions (Na, K) to control the
environment around neurons
–Regulate what substances reach the CNS from the blood
2. Recapture and recycle neurotransmitters.
3. Involved with synapse formation in developing neural tissue
4. Aid in repair of damaged neural tissue
5. Produce molecules necessary for neural growth.
2. Ependymal Cells
Line brain ventricles and spinal cord central canal.
–Specialized versions of ependymal form choroid plexuses.
Choroid plexus-secrete cerebrospinal fluid. Cilia help move fluid
through the cavities of the brain.
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3. Microglia –specialized macrophages. Respond to
inflammation, phagocytes necrotic tissue, microorganisms, and
foreign substances that invade the CNS.
4. Oligodendrocytes-form myelin sheaths if surrounding axon.
Single oligodendrocytes can form myelin sheaths around
portions of several axons.
Peripheral gilial cells
Schwann cells or neurolemmocytes:
–Wrap around portion of only one axon to form myelin sheath.
–Wrap around many times.
–As cells grow around axon, cytoplasm is squeezed out and
multiple layers of cell membrane wrap the axon.
–Outer surface of Schwann cell called the neurilemma
Satellite cells: surround neuron cell bodies in ganglia, provide
support and nutrients
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inflammation, phagocytes necrotic tissue, microorganisms, and
foreign substances that invade the CNS.
4. Oligodendrocytes-form myelin sheaths if surrounding axon.
Single oligodendrocytes can form myelin sheaths around
portions of several axons.
Peripheral gilial cells
Schwann cells or neurolemmocytes:
–Wrap around portion of only one axon to form myelin sheath.
–Wrap around many times.
–As cells grow around axon, cytoplasm is squeezed out and
multiple layers of cell membrane wrap the axon.
–Outer surface of Schwann cell called the neurilemma
Satellite cells: surround neuron cell bodies in ganglia, provide
support and nutrients
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Myelin Sheaths
•Segmented structures composed of the lipoprotein myelin
•Form an insulating layer
–Prevent leakage of electrical current
•Increase the speed of impulse conduction
•In the PNS, myelin sheaths form from neurolemmocytes
(Schwann cells).
•In the CNS, they form from oligodendrocytes.
•Myelination –formation of myelin sheath
•Neurilemma–material external to myelin layers
•Nodes of Ranvier –gaps along axon
•Degeneration of myelin sheaths occurs in multiple sclerosis and
some cases of diabetes mellitus.
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•Segmented structures composed of the lipoprotein myelin
•Form an insulating layer
–Prevent leakage of electrical current
•Increase the speed of impulse conduction
•In the PNS, myelin sheaths form from neurolemmocytes
(Schwann cells).
•In the CNS, they form from oligodendrocytes.
•Myelination –formation of myelin sheath
•Neurilemma–material external to myelin layers
•Nodes of Ranvier –gaps along axon
•Degeneration of myelin sheaths occurs in multiple sclerosis and
some cases of diabetes mellitus.
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Mylenated vs. Unmylenated Axons
•In a myelinated axon, the nerve impulse “jumps” from neurofibril
node to neurofibril node and is known as saltatory conduction.
•In an unmyelinated axon, the nerve impulse must travel the
entire length of the axon, a process called continuous
conduction.
•A myelinatedaxon produces a fasternerve impulse.
•In an unmyelinated axon, a nerve impulse takes longerto reach
the end of the axon.
•A myelinated axonalso requires less energy(ATP) than does
an unmyelinated axon.
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•In a myelinated axon, the nerve impulse “jumps” from neurofibril
node to neurofibril node and is known as saltatory conduction.
•In an unmyelinated axon, the nerve impulse must travel the
entire length of the axon, a process called continuous
conduction.
•A myelinatedaxon produces a fasternerve impulse.
•In an unmyelinated axon, a nerve impulse takes longerto reach
the end of the axon.
•A myelinated axonalso requires less energy(ATP) than does
an unmyelinated axon.
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Support and protection of the brain:
The brain is protected an isolated by multiple structures.
A. The bony cranium provides rigid support,
B. protective connective tissue membranes called meninges
surround and partition portions of the brain.
C. The blood-brain barrier to prevent entry of harmful materials from
the blood stream.
Cranial Meninges:
there are three connective tissue layers separates soft tissue
brain from the bone of cranium and enclosed and protect blood
vessel that supply the brain. contain and circulate cerebrospinal
fuild (CSF).
the cranial meninges are from the superficial to deep (close the
brain).
The brain is protected an isolated by multiple structures.
A. The bony cranium provides rigid support,
B. protective connective tissue membranes called meninges
surround and partition portions of the brain.
C. The blood-brain barrier to prevent entry of harmful materials from
the blood stream.
Cranial Meninges:
there are three connective tissue layers separates soft tissue
brain from the bone of cranium and enclosed and protect blood
vessel that supply the brain. contain and circulate cerebrospinal
fuild (CSF).
the cranial meninges are from the superficial to deep (close the
brain).
Meninges
The dura mater:
Dura Mater is an external tough, dense irregular connective
tissue layer composed of two fibrous layers.
The meningeal layer is usually fused to the periosteal layer,
except in specific areas where the two layers separate to form
large, blood filled spaces called Dura Venous Sinuses.
The dura venous sinusesare, in essence large veins that
drain blood from the brain and transport this blood to the
internal jugular veins.
The dura mater and the bones of the skull may be separated by
the potential epidural space,which contains the arteries and
veins that nourish the meninges and bones of the cranium.
Dura Mater is an external tough, dense irregular connective
tissue layer composed of two fibrous layers.
The meningeal layer is usually fused to the periosteal layer,
except in specific areas where the two layers separate to form
large, blood filled spaces called Dura Venous Sinuses.
The dura venous sinusesare, in essence large veins that
drain blood from the brain and transport this blood to the
internal jugular veins.
The dura mater and the bones of the skull may be separated by
the potential epidural space,which contains the arteries and
veins that nourish the meninges and bones of the cranium.
Arachnoid:
The arachnoid, also called the arachnoid mater or the
arachnoid membrane, lies immediately internal to the dura
mater.
Between the arachnoid and the over lying dura mater is a
potential space the subdural space, immediately deep to the
arachnoid is the subarachnoid space.
Pia mater:
The pia mater is the inner most of the cranial meninges.
It is a thin layer of delicate areolar connective tissue that tightly
adheres to the brain and follows every contour of the brain
surface.
The arachnoid, also called the arachnoid mater or the
arachnoid membrane, lies immediately internal to the dura
mater.
Between the arachnoid and the over lying dura mater is a
potential space the subdural space, immediately deep to the
arachnoid is the subarachnoid space.
Pia mater:
The pia mater is the inner most of the cranial meninges.
It is a thin layer of delicate areolar connective tissue that tightly
adheres to the brain and follows every contour of the brain
surface.
Brain Ventricles:
Ventricle are cavities or expansions with in the brain that are
derived from the plasma (opening) of the embryonic neural
tube.
There are four ventricles in the brain.
•Two lateral ventriclesare in the cerebrum, separated by a thin
medial partition called the septum pellucidum.
•With in the diencephalon is a smaller ventricle called the third
ventricle.
•Each lateral ventricle communicates with the third ventricle
through an opening called the inter ventricular foramen.
•A narrow canal called the mesencphalic (cerebral) aqueduct
passes through the mesenecephalon and connects the third
ventricle with the fourth ventricle.
All of the ventricle contain CSF.
Ventricle are cavities or expansions with in the brain that are
derived from the plasma (opening) of the embryonic neural
tube.
There are four ventricles in the brain.
•Two lateral ventriclesare in the cerebrum, separated by a thin
medial partition called the septum pellucidum.
•With in the diencephalon is a smaller ventricle called the third
ventricle.
•Each lateral ventricle communicates with the third ventricle
through an opening called the inter ventricular foramen.
•A narrow canal called the mesencphalic (cerebral) aqueduct
passes through the mesenecephalon and connects the third
ventricle with the fourth ventricle.
All of the ventricle contain CSF.
Cerebrospinal Fluid:
It is a clear color less liquid that circulates in the ventricles and sub
arachnoid space CSF performs several function.
A) Buoyancy: the brain floats in CSF, there by reducing it’s apparent
weight by more than 95% and preventing it from being crushed under
its own weight. With out CSF to support it the heavy brain would sink
though the foramen magnum.
B) Protection: CSF provides a liquid cushion to protect delicate
neural structures from sudden movements.
C) Environmental stability: CSF transports nutrients and chemical
messengers to the brain and remove waste products from the brain.
The waste products and excess CSF are eventually transported in to
the venous circulation.
It is a clear color less liquid that circulates in the ventricles and sub
arachnoid space CSF performs several function.
A) Buoyancy: the brain floats in CSF, there by reducing it’s apparent
weight by more than 95% and preventing it from being crushed under
its own weight. With out CSF to support it the heavy brain would sink
though the foramen magnum.
B) Protection: CSF provides a liquid cushion to protect delicate
neural structures from sudden movements.
C) Environmental stability: CSF transports nutrients and chemical
messengers to the brain and remove waste products from the brain.
The waste products and excess CSF are eventually transported in to
the venous circulation.
CSF Formation:
is formed by the choroid plexus in the ventricle. The choroid
plexus is composed of a layer of ependymal cells.
CSF is produced by secretion of a fluid from the ependymals
cells that originate from the blood plasma.
CSF Circulation:
The choroid plexus produces CSF at a rate of about 500
mililiters (ml) per day. The CSF eventually leaves the ventricles
and enters the subarachnoid space. where the total volume of
CSF at any given moment ranges between 100ml and 160ml.
this means that excess CSF is continuously removed from the
subarachnoid space so the fluid will not accumulate and
compress or damage the nervous tissue.
Excess CSF moves across the arachnoid membrane at the
arachnoid villi to return to the blood with in the dural venous
sinuses.
is formed by the choroid plexus in the ventricle. The choroid
plexus is composed of a layer of ependymal cells.
CSF is produced by secretion of a fluid from the ependymals
cells that originate from the blood plasma.
CSF Circulation:
The choroid plexus produces CSF at a rate of about 500
mililiters (ml) per day. The CSF eventually leaves the ventricles
and enters the subarachnoid space. where the total volume of
CSF at any given moment ranges between 100ml and 160ml.
this means that excess CSF is continuously removed from the
subarachnoid space so the fluid will not accumulate and
compress or damage the nervous tissue.
Excess CSF moves across the arachnoid membrane at the
arachnoid villi to return to the blood with in the dural venous
sinuses.
Blood Brain Barrier:
Nervous tissue is protected from the general circulation by the
blood brain barrier (BBB) which strictly regulates what
substances can enter the interstitial fluid of the brain.
The BBB prevents exposure of neurons in the brain to drugs,
waste products in the blood, and
variations in levels of normal substances (ions, Hormones) that
could adversely affect brain function.
BBB is markedly reduced or missing in three distinct locations
in the CNS :
The choroid plexus, hypothalamus, and pineal gland.
The capillaries of the choroid plexus must be permeable in
order to produce CSF.
Both the Hypothalamus and pineal gland produce some
hormones. Which must have ready access to the blood stream.
So their capillaries must be more permeable as well.
Nervous tissue is protected from the general circulation by the
blood brain barrier (BBB) which strictly regulates what
substances can enter the interstitial fluid of the brain.
The BBB prevents exposure of neurons in the brain to drugs,
waste products in the blood, and
variations in levels of normal substances (ions, Hormones) that
could adversely affect brain function.
BBB is markedly reduced or missing in three distinct locations
in the CNS :
The choroid plexus, hypothalamus, and pineal gland.
The capillaries of the choroid plexus must be permeable in
order to produce CSF.
Both the Hypothalamus and pineal gland produce some
hormones. Which must have ready access to the blood stream.
So their capillaries must be more permeable as well.
Blood-Brain Barrier
Basal lamina (cut)
Basal lamina (cut)
The four major region of brain:
The cerebrum The diencephalons
The brain steam The cerebellum.
1. CEREBRUM: the largest part of brain is divided in to right and
left hemispheres.
Cerebral hemispheres:
•The cerebrum is composed of two halves the right and left
cerebral hemisphere. paired cerebral hemisphere is
separated by a deep longitudinal fissurethat extends along
the mid sagittal plane.
•the largest of these white matter tracts, the corpus callosum
provides the main method of communication between these
hemispheres.
Lobes of cerebrum:
Each cerebral hemispheres is divided in to five
anatomically and functionally distinct lobes. these are: Frontal
lobe, parietal lobe, Temporal lobe, occipital lobe, insula,
The cerebrum The diencephalons
The brain steam The cerebellum.
1. CEREBRUM: the largest part of brain is divided in to right and
left hemispheres.
Cerebral hemispheres:
•The cerebrum is composed of two halves the right and left
cerebral hemisphere. paired cerebral hemisphere is
separated by a deep longitudinal fissurethat extends along
the mid sagittal plane.
•the largest of these white matter tracts, the corpus callosum
provides the main method of communication between these
hemispheres.
Lobes of cerebrum:
Each cerebral hemispheres is divided in to five
anatomically and functionally distinct lobes. these are: Frontal
lobe, parietal lobe, Temporal lobe, occipital lobe, insula,
A. Frontal lobe:lies deep to frontal bone and forms the anterior
part of the cerebral hemispheres. the frontal lobe ends
posteriorly at a deep groove is the central sulcus. The inferior
border of the frontal lobe is marked by the lateral sulcus.
NB; An importante anatomical feature of the frontal lobe is the
pre central gyrus.
B. parietal lobe:lies internal to the parietal bone and forms the
supro-posterior part of cerebral hemispheres. It terminates;
anteriorly at the central sulcus. posteriorly atparieto occipital
sulcus and laterally at lateral sulcus.
NB: an important anatomical feature of this lobe is the post
central gyrus.
C. temporal lobe: lies inferiorly to the lateral sulcus and lies the
temporal bone. This lobes involved with the hearing,
interpreting speech, and language, smell.
D. Occipital lobe:forms the posterior region of each
hemispheres and immediately under lies the occipital bone.
part of the cerebral hemispheres. the frontal lobe ends
posteriorly at a deep groove is the central sulcus. The inferior
border of the frontal lobe is marked by the lateral sulcus.
NB; An importante anatomical feature of the frontal lobe is the
pre central gyrus.
B. parietal lobe:lies internal to the parietal bone and forms the
supro-posterior part of cerebral hemispheres. It terminates;
anteriorly at the central sulcus. posteriorly atparieto occipital
sulcus and laterally at lateral sulcus.
NB: an important anatomical feature of this lobe is the post
central gyrus.
C. temporal lobe: lies inferiorly to the lateral sulcus and lies the
temporal bone. This lobes involved with the hearing,
interpreting speech, and language, smell.
D. Occipital lobe:forms the posterior region of each
hemispheres and immediately under lies the occipital bone.
Occipital lobe is responsible for processing incoming visual
information and store visual memories.
E. Insula:is the small lobe deep to lateral sulcus. Involved in
memory and the inter pretation of taste.
Functional areas of the cerebrum
Three categories of functional areas are recognized :
A. Motor areas:that control voluntary motor functions.
B. Sensory areas:that provide conscious awareness of
sensation and
C. Association areas:that primarily integrate and store
information.
Motor Area
•The cortical areas that control motor functions are housed with
in the frontal lobes. The primary motor cortex, also called the
somatic motor area, is located with in the precentral gyrus of
the frontal lobe.
information and store visual memories.
E. Insula:is the small lobe deep to lateral sulcus. Involved in
memory and the inter pretation of taste.
Functional areas of the cerebrum
Three categories of functional areas are recognized :
A. Motor areas:that control voluntary motor functions.
B. Sensory areas:that provide conscious awareness of
sensation and
C. Association areas:that primarily integrate and store
information.
Motor Area
•The cortical areas that control motor functions are housed with
in the frontal lobes. The primary motor cortex, also called the
somatic motor area, is located with in the precentral gyrus of
the frontal lobe.
Motor Areas
•The axons of these neurons project contra laterally (to the
opposite side) to the brain stem and spinal cord. Thus the left
primary motor cortex controls the right side voluntary muscles,
and vice versa.
Sensory Areas :
The cortical area with in the parietal, temporal and occipital
lobes are involved with conscious awareness of sensation.
The primary somato sensory cortex: is housed with in the
post central gyrus of the parietal lobes. Neurons in this cortex
receive general somatic sensory information from touch
pressure, pain and temperature receptors.
sensory information for sight, sound, taste and smell:
arrives at other cortical regions.
The primary visiual cortex: located in the occipital lobe,
receives and processes incoming visual information.
The primary auditory cortex: located in the temporal lobe,
receives and processes auditory information.
opposite side) to the brain stem and spinal cord. Thus the left
primary motor cortex controls the right side voluntary muscles,
and vice versa.
Sensory Areas :
The cortical area with in the parietal, temporal and occipital
lobes are involved with conscious awareness of sensation.
The primary somato sensory cortex: is housed with in the
post central gyrus of the parietal lobes. Neurons in this cortex
receive general somatic sensory information from touch
pressure, pain and temperature receptors.
sensory information for sight, sound, taste and smell:
arrives at other cortical regions.
The primary visiual cortex: located in the occipital lobe,
receives and processes incoming visual information.
The primary auditory cortex: located in the temporal lobe,
receives and processes auditory information.
The gustatory (taste) cortex: is in the insula and is involved in
processing taste information.
The olfactory (smell) cortex: located in the temporal lobe,
provides conscious awareness of smells.
Association Areas
The primary motor and sensory cortical regions are connected
to adjacent association areas that process and interpret
incoming data.
Following are description of main association areas :
oThe pre motor cortex: also called the somatic motor
association area is located in the Frontal lobe, immediately
anterior to the pre central gyres. It is primarily responsible for
coordinating learned, skilled motor activities, such as playing
the piano.
oThe somato sensory association area: is located in the
parietal lobe and lies immediately posterior to the primary
somato sensory cortex.
processing taste information.
The olfactory (smell) cortex: located in the temporal lobe,
provides conscious awareness of smells.
Association Areas
The primary motor and sensory cortical regions are connected
to adjacent association areas that process and interpret
incoming data.
Following are description of main association areas :
oThe pre motor cortex: also called the somatic motor
association area is located in the Frontal lobe, immediately
anterior to the pre central gyres. It is primarily responsible for
coordinating learned, skilled motor activities, such as playing
the piano.
oThe somato sensory association area: is located in the
parietal lobe and lies immediately posterior to the primary
somato sensory cortex.
oIt integrates and interprets sensations to determine the texture,
temperature, pressure and shape of objects.
oThe auditory association area: is located with in the temporal
lobe, postero inferior to the primary auditory cortex, with in this
area the cortical neurons interpret the characteristics of sound
and store memories of sound heard in the past.
oThe visual association area: Is located the occipital lobe and
surrounding the primary visual area. It enables us to process
visual information by analyzing color movement, and form and
to use this information to identify the things we see.
temperature, pressure and shape of objects.
oThe auditory association area: is located with in the temporal
lobe, postero inferior to the primary auditory cortex, with in this
area the cortical neurons interpret the characteristics of sound
and store memories of sound heard in the past.
oThe visual association area: Is located the occipital lobe and
surrounding the primary visual area. It enables us to process
visual information by analyzing color movement, and form and
to use this information to identify the things we see.
Diencephalon:
•is a part of the prosencephalon between the inferior regions of
the cerebral hemisphere. This regions is often referred to as the
“in-between-Brain”.
•The components of diencephalon including thalamus,
epithalamus, hypothalamus.
•The diencephalon provides the relay and switching centers for
some sensory and motor pathways and for central of visceral
activities.
Epithalamus
•The epithalamus partially forms the posterior roof of the
diencephalon and covers the third ventricle.
Thalamus:
•The thalamus refers to paired oval masses of gray matter that
on either side of the third ventricle.
lateral geniculate nuclei: Relay visual information ffrom optic
tract to visual cortex and mid brain.
•is a part of the prosencephalon between the inferior regions of
the cerebral hemisphere. This regions is often referred to as the
“in-between-Brain”.
•The components of diencephalon including thalamus,
epithalamus, hypothalamus.
•The diencephalon provides the relay and switching centers for
some sensory and motor pathways and for central of visceral
activities.
Epithalamus
•The epithalamus partially forms the posterior roof of the
diencephalon and covers the third ventricle.
Thalamus:
•The thalamus refers to paired oval masses of gray matter that
on either side of the third ventricle.
lateral geniculate nuclei: Relay visual information ffrom optic
tract to visual cortex and mid brain.
Thalamus
Thalamus
Medial geniculate nuclei: relay auditory information from
inner ear to auditory cortex.
Hypothalamus:
•The hypothalamus is the antero inferior region of the
diencephalon. The thin, stalk like infundibulum extends
inferiorly form the hypothalamus to attach to the pituitary gland.
Brain Stem:
It connects the proscencephalon and cerebellum to the spinal
cord. Three regions form the brain stem from superior to
inferior mesencephalon, pons, and medulla oblongata.
The brain steam is a bidirectional passage way for all tracts
extending b/n the cerebrum and the spinal cord.
It also contains many autonomic centers and reflex centers
required for out survival and it house nuclei of many of the
cranial nerves.
inner ear to auditory cortex.
Hypothalamus:
•The hypothalamus is the antero inferior region of the
diencephalon. The thin, stalk like infundibulum extends
inferiorly form the hypothalamus to attach to the pituitary gland.
Brain Stem:
It connects the proscencephalon and cerebellum to the spinal
cord. Three regions form the brain stem from superior to
inferior mesencephalon, pons, and medulla oblongata.
The brain steam is a bidirectional passage way for all tracts
extending b/n the cerebrum and the spinal cord.
It also contains many autonomic centers and reflex centers
required for out survival and it house nuclei of many of the
cranial nerves.
Mesencephalon(mid brain):
Is the rostra (superior) portion of the brain stem.
Mesencephalic aqueducte extending through the
mesenephalon , that connecting the third and fourth ventricles.
The nuclei of two cranial nerves that control some eye
movements are housed in the mesencephalon the oculo
motor nerve(CN III) and the trochlear nerveCN IV).
It contains two pairs of sensory nuclei.
The superior and inferior colliculi which are collectively called
the corpora quadrigemina.
These nuclei are relay stations in the processing pathway of visual
and auditory sensations.
Is the rostra (superior) portion of the brain stem.
Mesencephalic aqueducte extending through the
mesenephalon , that connecting the third and fourth ventricles.
The nuclei of two cranial nerves that control some eye
movements are housed in the mesencephalon the oculo
motor nerve(CN III) and the trochlear nerveCN IV).
It contains two pairs of sensory nuclei.
The superior and inferior colliculi which are collectively called
the corpora quadrigemina.
These nuclei are relay stations in the processing pathway of visual
and auditory sensations.
The Midbrain
Pons:
oIt is a bulging region on the anterior part of the brain stem
that forms from part of the metencephalon.
oHoused with in the Pons are sensory and motor tracts that
run through the Pons and connect to the brain and spinal
cord.
oThe middle cerebellar peduncles are transverse fibers that
connect the Pons to the cerebellum.
oThe Pons also houses two autonomic respiratory centers.
The pneumotaxic center
The apneustic center
These centers regulate the rate and depth of breathing.
oThe pons houses sensory and motor cranial nerve nuclei for
trigeminal (CNV),
abducens (CN VI),
facial (CN VII)cranial nerves.
nuclei for the vestibule cochleorcranial nerve (CN VIII) are located
there.
oIt is a bulging region on the anterior part of the brain stem
that forms from part of the metencephalon.
oHoused with in the Pons are sensory and motor tracts that
run through the Pons and connect to the brain and spinal
cord.
oThe middle cerebellar peduncles are transverse fibers that
connect the Pons to the cerebellum.
oThe Pons also houses two autonomic respiratory centers.
The pneumotaxic center
The apneustic center
These centers regulate the rate and depth of breathing.
oThe pons houses sensory and motor cranial nerve nuclei for
trigeminal (CNV),
abducens (CN VI),
facial (CN VII)cranial nerves.
nuclei for the vestibule cochleorcranial nerve (CN VIII) are located
there.
Medulla Oblongata:
is formed from the Myelencephalon. It is the most caudal
(inferior) part of the brain stem and is continuous with the spinal
cord inferiorly.
•All communication between the brain and spinal cord involves
tracts that ascend or descend through the medulla oblongata.
•The anterior surface exhibits two longitudinal ridges called the
pyramids.
•In the caudal region of the medulla, most of these pyramidal
axons cross to the opposite side of the brain at a point called
the decussation of the pyramids.
•. The cranial nerves nuclei are associated with the vestibule
cochleor (CN VIII), gloss pharyngeal (CN IX), vague (CN X),
accessory (CN XI) and Hypoglossal (CN XII)cranial nerves.
Finally, the medulla contains several autonomic nuclei, which
regulate functions vital for life.
The most important Autonomic centerin the Medulla are :
I. The cardiac center: regulates both the heart’s rate and it’s
strength of contraction.
is formed from the Myelencephalon. It is the most caudal
(inferior) part of the brain stem and is continuous with the spinal
cord inferiorly.
•All communication between the brain and spinal cord involves
tracts that ascend or descend through the medulla oblongata.
•The anterior surface exhibits two longitudinal ridges called the
pyramids.
•In the caudal region of the medulla, most of these pyramidal
axons cross to the opposite side of the brain at a point called
the decussation of the pyramids.
•. The cranial nerves nuclei are associated with the vestibule
cochleor (CN VIII), gloss pharyngeal (CN IX), vague (CN X),
accessory (CN XI) and Hypoglossal (CN XII)cranial nerves.
Finally, the medulla contains several autonomic nuclei, which
regulate functions vital for life.
The most important Autonomic centerin the Medulla are :
I. The cardiac center: regulates both the heart’s rate and it’s
strength of contraction.
II. The vasomotor center:controls blood pressure by regulating
the contraction and relaxation of smooth muscle in the walls of
the smallest arteries. Blood pressure increase when vessels
walls are constricted and lowers when vessel walls are dilated.
III. The Respiratory Center:regulates the respiratory rate. It is
influenced by the apneustic and pneumotaxic centers of the
pons.
IV. Other nuclei in the medulla re involved in coughing, sneezing,
salivation, swallowing, gagging and vomiting.
Cerebellum
The cerebellum is the second largest part of the brain, and it
develops from the Metencephalon.
The cerebellum has a complex, highly convoluted surface covered
by a layer of cerebellar cortex.
Cerebellar Peduncles:
Three thick tracts, called peduncles, link the cerebellum with
the brain stem.
•The superior cerebellar peduncles: connects the cerebellum
to the Mesencephalon.
the contraction and relaxation of smooth muscle in the walls of
the smallest arteries. Blood pressure increase when vessels
walls are constricted and lowers when vessel walls are dilated.
III. The Respiratory Center:regulates the respiratory rate. It is
influenced by the apneustic and pneumotaxic centers of the
pons.
IV. Other nuclei in the medulla re involved in coughing, sneezing,
salivation, swallowing, gagging and vomiting.
Cerebellum
The cerebellum is the second largest part of the brain, and it
develops from the Metencephalon.
The cerebellum has a complex, highly convoluted surface covered
by a layer of cerebellar cortex.
Cerebellar Peduncles:
Three thick tracts, called peduncles, link the cerebellum with
the brain stem.
•The superior cerebellar peduncles: connects the cerebellum
to the Mesencephalon.
•The middle cerebellar peduncles: connect the pons to the
cerebellum.
•The inferior cerebellar peduncles: connects the cerebellum
to medulla oblongata.
It is these extensive communications that enable the
cerebellum to “Fine tune” skeletal muscle movements and
interpret all body proprioceptive movement.
Spinal Cord and Spinal Nerves:
The spinal cord and its attach spinal nerves serve two important
functions.
First: they are a pathway for sensory and motor impulses.
Second: the spinal cord and spinal nerves are responsible for
reflexes, which are our quickest reactions to a stimulus.
Gross Anatomy of the spinal cord.
•A typical adult spinal cord ranges between 42 and 45cm in
length. Its external surface has two longitudinal depressions.
cerebellum.
•The inferior cerebellar peduncles: connects the cerebellum
to medulla oblongata.
It is these extensive communications that enable the
cerebellum to “Fine tune” skeletal muscle movements and
interpret all body proprioceptive movement.
Spinal Cord and Spinal Nerves:
The spinal cord and its attach spinal nerves serve two important
functions.
First: they are a pathway for sensory and motor impulses.
Second: the spinal cord and spinal nerves are responsible for
reflexes, which are our quickest reactions to a stimulus.
Gross Anatomy of the spinal cord.
•A typical adult spinal cord ranges between 42 and 45cm in
length. Its external surface has two longitudinal depressions.
The spinal cord may be subdivided in to the following regions :
•The cervical region: is the superior most region of the spinal
cord. It is continuous with the medulla oblongata. The cervical
region contains motor neurons whose axons contribute to the
cervical spinal nerves.
•The thoracic region: lies inferior to the cervical region. It
contains the motor neurons for the thoracic spinal nerves.
The lumbar region: is a shorter segment of the spinal cord that
contains the motor neurons for the lumbar spinal nerve.
•The sacrals regions: lies inferior to the lumbar region and
contains the motor neurons for the sacral spinal nerves.
•The coccygeal region: is the most inferior “tip” of the spinal
cord. One pair of coccygeal spinal nerves arises from this
region.
The spinal cord is associated with 31 pairs of spinal nerves that
connect the CNS to muscles, receptors, and glands.
•The cervical region: is the superior most region of the spinal
cord. It is continuous with the medulla oblongata. The cervical
region contains motor neurons whose axons contribute to the
cervical spinal nerves.
•The thoracic region: lies inferior to the cervical region. It
contains the motor neurons for the thoracic spinal nerves.
The lumbar region: is a shorter segment of the spinal cord that
contains the motor neurons for the lumbar spinal nerve.
•The sacrals regions: lies inferior to the lumbar region and
contains the motor neurons for the sacral spinal nerves.
•The coccygeal region: is the most inferior “tip” of the spinal
cord. One pair of coccygeal spinal nerves arises from this
region.
The spinal cord is associated with 31 pairs of spinal nerves that
connect the CNS to muscles, receptors, and glands.
Thus, each side of the spinal cord contains:
A. 8 Cervical Nerves (C1 –C8)
B. 12 Thoracic Nerves (T1 –T12)
C. 5 Lumbar Nerves (L1 –L5)
D. 5 Sacral Nerves (S1 –S5) and
E. 1 Coccygeal Nerves (Co)
Spinal Cord Meninges
•The spinal cord is protected and encapsulated by spinal cord
meninges, which are continuous with the cranial meninges.
•In addition, space between some of the meninges have clinigal
significance.
•The structures and spaces that encircle the spinal cord.
•Listed from outer most to inner most are as follows Vertebra
Epidural space dura matter subdural space arachnoid
subarachnoid space and finally pia matter.
A. 8 Cervical Nerves (C1 –C8)
B. 12 Thoracic Nerves (T1 –T12)
C. 5 Lumbar Nerves (L1 –L5)
D. 5 Sacral Nerves (S1 –S5) and
E. 1 Coccygeal Nerves (Co)
Spinal Cord Meninges
•The spinal cord is protected and encapsulated by spinal cord
meninges, which are continuous with the cranial meninges.
•In addition, space between some of the meninges have clinigal
significance.
•The structures and spaces that encircle the spinal cord.
•Listed from outer most to inner most are as follows Vertebra
Epidural space dura matter subdural space arachnoid
subarachnoid space and finally pia matter.
Sectional anatomy of the spinal cord
•The spinal cord is partitioned into an inner gray matterregion
and an outer white matterregion.
•The gray matter is dominated by the dendrites and cell bodies
of neurons and glial cells and unmyelinated axons,
•where as the white matter is composed primarily of Myelinated
axons.
Location and Distribution of Gray Matter
•The grey matter in the spinal cord is centrally located, and its
shape resembles a letter H or a butterfly.
•The grey matter may be subdivided into the following
components :Anterior horns, lateral horns, posterior horns
and the gray commissural.
Anterior horns: are the left and right anterior masses of gray
matter.
The anterior horns primarily house the cell bodies of somatic
motor neurons, which innervate skeletal muscle.
•The spinal cord is partitioned into an inner gray matterregion
and an outer white matterregion.
•The gray matter is dominated by the dendrites and cell bodies
of neurons and glial cells and unmyelinated axons,
•where as the white matter is composed primarily of Myelinated
axons.
Location and Distribution of Gray Matter
•The grey matter in the spinal cord is centrally located, and its
shape resembles a letter H or a butterfly.
•The grey matter may be subdivided into the following
components :Anterior horns, lateral horns, posterior horns
and the gray commissural.
Anterior horns: are the left and right anterior masses of gray
matter.
The anterior horns primarily house the cell bodies of somatic
motor neurons, which innervate skeletal muscle.
Lateral horns: are found in the T1 –L2 regions of the spinal
cord only. The lateral horns contain the cell bodies of autonomic
motor neurons, which innervate cardiac muscle, smooth muscle
and glands.
Posterior horns: are the left and right posterior masses of
gray matter. The axons of sensory neurons and the cell bodies
of inter neurons are located in the posterior horns.
•(Note that the cell bodies of these sensory neurons are not
found in the posterior horns. Rather They are located in the
posterior (dorsal) root ganglia.
The gray commissure: is a horizontal bar of gray matter that
surrounds a narrow central canal. The gray commisure
primarily contains un myelinated axons and serves as a
communication route between the right and left sides of the
gray matter.
cord only. The lateral horns contain the cell bodies of autonomic
motor neurons, which innervate cardiac muscle, smooth muscle
and glands.
Posterior horns: are the left and right posterior masses of
gray matter. The axons of sensory neurons and the cell bodies
of inter neurons are located in the posterior horns.
•(Note that the cell bodies of these sensory neurons are not
found in the posterior horns. Rather They are located in the
posterior (dorsal) root ganglia.
The gray commissure: is a horizontal bar of gray matter that
surrounds a narrow central canal. The gray commisure
primarily contains un myelinated axons and serves as a
communication route between the right and left sides of the
gray matter.
Location and Distribution of white matter
•The white matter of the spinal cord is external to the gray
matter. White matter on each side of the cord is also portioned
in to three regions, each called a funiculus.
The posterior funiculus:lies between the posterior gray horns
on the posterior side of the cord and the posterior median
sulcus.
The white matter region on each lateral side of the spinal cord
is the lateral funiculus.
The anterior funiculus: is composed of tracts of white matter
that occupy the space on each anterior side of the cord
between the anterior gray horns and the anterior median
fissure.
•The anterior funiculi are inter connected by the white
commissure.
•The axons with in each white matter funiculus are organized
into smaller structural units called tracts.
•The white matter of the spinal cord is external to the gray
matter. White matter on each side of the cord is also portioned
in to three regions, each called a funiculus.
The posterior funiculus:lies between the posterior gray horns
on the posterior side of the cord and the posterior median
sulcus.
The white matter region on each lateral side of the spinal cord
is the lateral funiculus.
The anterior funiculus: is composed of tracts of white matter
that occupy the space on each anterior side of the cord
between the anterior gray horns and the anterior median
fissure.
•The anterior funiculi are inter connected by the white
commissure.
•The axons with in each white matter funiculus are organized
into smaller structural units called tracts.
Individual tracts conduct either sensory impulses (ascending
tracts from the spinal cord to the brain) or motor commands
(descending tracts from the brain to the spinal cord) only.
Each funicular region (posterior , lateral and anterior) contains
both ascending and descending tracts.
Thus, each funiculus contains axons of both motor and sensory
nerves.
Spinal Nerves
•The 31 pairs of spinal nerves connect the CNS to muscles,
glands and receptors.
•Each spinal nerve is formed form the union of thousands of
motor and sensory axons.
•Motor axons originate from the spinal cord.
Spinal Nerve Distribution
A typical spinal nerve almost immediately splits in to branches,
termed rami.
tracts from the spinal cord to the brain) or motor commands
(descending tracts from the brain to the spinal cord) only.
Each funicular region (posterior , lateral and anterior) contains
both ascending and descending tracts.
Thus, each funiculus contains axons of both motor and sensory
nerves.
Spinal Nerves
•The 31 pairs of spinal nerves connect the CNS to muscles,
glands and receptors.
•Each spinal nerve is formed form the union of thousands of
motor and sensory axons.
•Motor axons originate from the spinal cord.
Spinal Nerve Distribution
A typical spinal nerve almost immediately splits in to branches,
termed rami.
The posterior (dorsal) ramus: is the smaller of the two main
branches. It innervates the deep muscles of the back and the
skin of the back.
•The anterior (Ventral) ramus:is the larger of the two main
branches, which innervate the anterior and lateral portions of
the trunk, the upper limbs and the lower limbs.
•Vasculature
Arteries:The arterial supply to the spinal cord comes from two
sources. It consists of:
•longitudinally oriented vessels, arising superior to the cervical
portion of the cord, which descend on the surface of the cord;
•feeder arteries that enter the vertebral canal through the
intervertebral foramina at every level-these feeder vessels, or
segmental spinal arteries.
branches. It innervates the deep muscles of the back and the
skin of the back.
•The anterior (Ventral) ramus:is the larger of the two main
branches, which innervate the anterior and lateral portions of
the trunk, the upper limbs and the lower limbs.
•Vasculature
Arteries:The arterial supply to the spinal cord comes from two
sources. It consists of:
•longitudinally oriented vessels, arising superior to the cervical
portion of the cord, which descend on the surface of the cord;
•feeder arteries that enter the vertebral canal through the
intervertebral foramina at every level-these feeder vessels, or
segmental spinal arteries.
Nerve Plexuses:
is a network of inter weaving anterior rami of spinal nerves.
The anterior rami of most spinal nerves form nerve plexuses on
both the right and left sides of the body. The principal plexuses
are :-
A. The cervical plexuse
B. The brachial plexuse
C. The lumbar plexuse
D. The sacral plexuse
Cervical Plexuses: The left and right cervical plexuses are
located deep on each side of the neck, immediately lateral to
cervical vertebrae C1 –C4.
•They are formed primarily by the anterior rami of spinal nerves
C1 –C4.
•Branches of the cervical plexuses innervate anterior neck
muscles as well as the skin of the neck and portions of the
head and shoulders.
is a network of inter weaving anterior rami of spinal nerves.
The anterior rami of most spinal nerves form nerve plexuses on
both the right and left sides of the body. The principal plexuses
are :-
A. The cervical plexuse
B. The brachial plexuse
C. The lumbar plexuse
D. The sacral plexuse
Cervical Plexuses: The left and right cervical plexuses are
located deep on each side of the neck, immediately lateral to
cervical vertebrae C1 –C4.
•They are formed primarily by the anterior rami of spinal nerves
C1 –C4.
•Branches of the cervical plexuses innervate anterior neck
muscles as well as the skin of the neck and portions of the
head and shoulders.
Brachial Plexuses: The left and right brachial plexuses are networks of
nerves that supply the upper limb. Each brachial plexuses is formed
by the anterior rami of spinal nerves C5 –T1. Each Brachial plexuses
innervates the pectoral girdle and the entire upper limb of one side.
Terminal Branch Anterior Rami ofBrachial Plexus:
Axillary nerve (C5, C6):Formed from posterior cord, posterior
division of the brachial plexus.
Median nerve (C5, T1):Formed from medial and lateral cords,
anterior division of the brachial plexus.
Radial Nerve (C5, T1):Formed from the posterior cord, posterior
division of the brachial plexus.
Musculo cutaneous nerve (C5 –C7): Formed from the lateral cord,
anterior division of the brachial plexus.
Ulnar Nerve (C8 –T1):Formed from the medial cord, anterior
division of the brachial plexus.
nerves that supply the upper limb. Each brachial plexuses is formed
by the anterior rami of spinal nerves C5 –T1. Each Brachial plexuses
innervates the pectoral girdle and the entire upper limb of one side.
Terminal Branch Anterior Rami ofBrachial Plexus:
Axillary nerve (C5, C6):Formed from posterior cord, posterior
division of the brachial plexus.
Median nerve (C5, T1):Formed from medial and lateral cords,
anterior division of the brachial plexus.
Radial Nerve (C5, T1):Formed from the posterior cord, posterior
division of the brachial plexus.
Musculo cutaneous nerve (C5 –C7): Formed from the lateral cord,
anterior division of the brachial plexus.
Ulnar Nerve (C8 –T1):Formed from the medial cord, anterior
division of the brachial plexus.
Lumbar Plexuses: The left and right lumbar plexuses are formed
from the anterior rami of spinal nerves L1 –L4. located lateral
to the L1 –L4 vertebrae and with in the psoas major muscle in
the posterior abdominal wall.
Sacral Plexuses:The left and right sacral plexuses are formed
form the anterior rami of spinal nerves L4 –S5 and are located
immediately inferior to the lumbar plexuses.
Reflexes :
Reflexes are rapid, automatic, involuntary reactions of muscles
or glands to a stimulus.
A reflex arc is the neural “wiring” of a single reflex. It always
begin at a receptor in the PNS, communicates with the CNS,
and ends at a peripheral effector, such as a muscle or gland
cell.
from the anterior rami of spinal nerves L1 –L4. located lateral
to the L1 –L4 vertebrae and with in the psoas major muscle in
the posterior abdominal wall.
Sacral Plexuses:The left and right sacral plexuses are formed
form the anterior rami of spinal nerves L4 –S5 and are located
immediately inferior to the lumbar plexuses.
Reflexes :
Reflexes are rapid, automatic, involuntary reactions of muscles
or glands to a stimulus.
A reflex arc is the neural “wiring” of a single reflex. It always
begin at a receptor in the PNS, communicates with the CNS,
and ends at a peripheral effector, such as a muscle or gland
cell.
Five steps are involved in a neural reflex :
1) Stimulus activates receptor
2) Nerve impulse travels through sensory neuron to the
CNS.
3) Information from nerve impulse is processed in the
integration center by inter neurons.
4) Motor neuron transmits nerve impulse to effector.
5) Effector responds to nerve impulse from motor neuron.
1) Stimulus activates receptor
2) Nerve impulse travels through sensory neuron to the
CNS.
3) Information from nerve impulse is processed in the
integration center by inter neurons.
4) Motor neuron transmits nerve impulse to effector.
5) Effector responds to nerve impulse from motor neuron.
Reflex arcs may be ipsilateral or contralateral.
•A reflex arc is termed ipsilateral when both the receptor and
effector organs of the reflex are on the same side of the spinal
cord. For example
•E.g. 1An ipsilateral effect occurs when the muscles in your left
arm contract to pull your left hand away from a hot objects.
•A reflex arc is contra lateral when the sensory impulse from a
receptor organ cross over through the spinal cord, to activate
effector organs in the opposite limb.
•E.g. 2Contra lateral effect occurs when you step on a sharp
object with your left foot and then contract the muscles in your
right leg to maintain balance as you with draw your left leg.
From the damaging object.
•A reflex arc is termed ipsilateral when both the receptor and
effector organs of the reflex are on the same side of the spinal
cord. For example
•E.g. 1An ipsilateral effect occurs when the muscles in your left
arm contract to pull your left hand away from a hot objects.
•A reflex arc is contra lateral when the sensory impulse from a
receptor organ cross over through the spinal cord, to activate
effector organs in the opposite limb.
•E.g. 2Contra lateral effect occurs when you step on a sharp
object with your left foot and then contract the muscles in your
right leg to maintain balance as you with draw your left leg.
From the damaging object.
•The somatic motor system innervates only skeletal muscle,
stimulating voluntary and reflexive movement
Autonomic Nervous System
•The autonomic nervous system, classically described as the
visceral nervous system or visceral motor system, consists of
motor fibers that stimulate smooth (involuntary) muscle, modified
cardiac muscle (the intrinsic stimulating and conducting tissue of
heart), and glandular (secretory) cells.
ANS are organized into two systems or divisions:
•sympathetic (thoracolumbar) division
•Parasympathetic (craniosacral) division
stimulating voluntary and reflexive movement
Autonomic Nervous System
•The autonomic nervous system, classically described as the
visceral nervous system or visceral motor system, consists of
motor fibers that stimulate smooth (involuntary) muscle, modified
cardiac muscle (the intrinsic stimulating and conducting tissue of
heart), and glandular (secretory) cells.
ANS are organized into two systems or divisions:
•sympathetic (thoracolumbar) division
•Parasympathetic (craniosacral) division
Sympathetic (Thoracolumbar) Division of the ANS
•The cell bodies of the presynaptic neurons of the sympathetic
division of the ANS are found in only one location:
•the intermediolateral cell columns (IMLs) or nuclei of the spinal
cord.
•The paired (right and left) IMLs are a part of the gray matter of
the thoracic (T1-12) and the upper lumbar (T1-L2 or 3)
segments of the spinal cord .
Parasympathetic (Craniosacral) Division of the ANS
•Presynaptic parasympathetic neuron cell bodies are located in
two sites within the CNS, their fibers exiting by two routes.
•The cell bodies of the presynaptic neurons of the sympathetic
division of the ANS are found in only one location:
•the intermediolateral cell columns (IMLs) or nuclei of the spinal
cord.
•The paired (right and left) IMLs are a part of the gray matter of
the thoracic (T1-12) and the upper lumbar (T1-L2 or 3)
segments of the spinal cord .
Parasympathetic (Craniosacral) Division of the ANS
•Presynaptic parasympathetic neuron cell bodies are located in
two sites within the CNS, their fibers exiting by two routes.
•This arrangement accounts for the alternate name of the
parasympathetic (craniosacral) division of the ANSIn the gray
matter of the brainstem, the fibers exit the CNS within cranial
nerves (CN) III, VII, IX, and X;
•these fibers constitute the cranial parasympathetic outflow.
•In the gray matter of the sacral segments of the spinal cord (S2-
4), the fibers exit the CNS through the anterior roots of sacral
spinal nerves S2 -4 and the pelvic splanchnic nerves that
arise from their anterior rami;
•these fibers constitute the sacral parasympathetic outflow
parasympathetic (craniosacral) division of the ANSIn the gray
matter of the brainstem, the fibers exit the CNS within cranial
nerves (CN) III, VII, IX, and X;
•these fibers constitute the cranial parasympathetic outflow.
•In the gray matter of the sacral segments of the spinal cord (S2-
4), the fibers exit the CNS through the anterior roots of sacral
spinal nerves S2 -4 and the pelvic splanchnic nerves that
arise from their anterior rami;
•these fibers constitute the sacral parasympathetic outflow
•The cranial outflow provides parasympathetic innervation of the
head, and the sacral outflow provides the parasympathetic
innervation of the pelvic viscera.
•The cranial outflow through the vagus nerve (CN X) is
dominant. It provides innervation to all the thoracic viscera and
most of the gastrointestinal (GI) tract from the esophagus .
•The sacral outflow to the GI tract supplies only the descending
and sigmoid colon and rectum.
head, and the sacral outflow provides the parasympathetic
innervation of the pelvic viscera.
•The cranial outflow through the vagus nerve (CN X) is
dominant. It provides innervation to all the thoracic viscera and
most of the gastrointestinal (GI) tract from the esophagus .
•The sacral outflow to the GI tract supplies only the descending
and sigmoid colon and rectum.
•Functions of the Divisions of the ANS.
•Sympathetic system is a catabolic (energy-expending)
system that enables the body to deal with stresses, such as
when preparing the body for the fight-or-flight response.
•The parasympathetic system is primarily a homeostatic or
anabolic (energy-conserving) system, promoting the quiet
and orderly processes of the body, such as those that allow the
body to feed and assimilate.
•The autonomic nervous system is a sub-division of the motor
nervous system that controls functions of the body not under
conscious control.
•Sympathetic system is a catabolic (energy-expending)
system that enables the body to deal with stresses, such as
when preparing the body for the fight-or-flight response.
•The parasympathetic system is primarily a homeostatic or
anabolic (energy-conserving) system, promoting the quiet
and orderly processes of the body, such as those that allow the
body to feed and assimilate.
•The autonomic nervous system is a sub-division of the motor
nervous system that controls functions of the body not under
conscious control.
2) Peripheral Nervous System
•Connect the CNS with peripheral structures
•Made up of nerve fibersand cell bodies
•A peripheral nerve fiber is composed of an axon, a single
process of a neuron
•Peripheral nerves are protected by threeconnective tissue
coverings
•Endoneurium-Surrounds the neurolemma cells and axons
•Perineurium-Encloses a fascicle (bundle) of peripheral
nerve fibers, barrier against penetration of
foreign substances
•Epineurium-Surrounds and encloses a bundle of fascicles,
the outermost covering of the nerve
•It includes fatty tissues, blood vessels, and
lymphatics.
•Connect the CNS with peripheral structures
•Made up of nerve fibersand cell bodies
•A peripheral nerve fiber is composed of an axon, a single
process of a neuron
•Peripheral nerves are protected by threeconnective tissue
coverings
•Endoneurium-Surrounds the neurolemma cells and axons
•Perineurium-Encloses a fascicle (bundle) of peripheral
nerve fibers, barrier against penetration of
foreign substances
•Epineurium-Surrounds and encloses a bundle of fascicles,
the outermost covering of the nerve
•It includes fatty tissues, blood vessels, and
lymphatics.
Peripheral nerves and Associated structures
•A nerve is a cordlike
organ that is part of the
peripheral nervous
system
•Every nerve consists of
parallel bundles of
peripheral axons
enclosed by successive
wrappings of connective
tissue
•A nerve is a cordlike
organ that is part of the
peripheral nervous
system
•Every nerve consists of
parallel bundles of
peripheral axons
enclosed by successive
wrappings of connective
tissue
Peripheral Nervous System …
•A collection of nerve cell bodies outside the CNS is a
ganglion
•Peripheral nerves are
–Cranial(CN)---12 pairs arise from the
•All cranial nerves exit the cranial cavity through foramina in
the cranium (G. kranion, skull)
–Spinal nerves ---31 pairs arise from the spinal cord
–8 cervical (C), 12 thoracic (T), 5 lumbar (L), 5 sacral (S),
and 1 coccygeal (Co)
–All spinal nerves exit through intervertebral foramina in
the vertebral column.
•A collection of nerve cell bodies outside the CNS is a
ganglion
•Peripheral nerves are
–Cranial(CN)---12 pairs arise from the
•All cranial nerves exit the cranial cavity through foramina in
the cranium (G. kranion, skull)
–Spinal nerves ---31 pairs arise from the spinal cord
–8 cervical (C), 12 thoracic (T), 5 lumbar (L), 5 sacral (S),
and 1 coccygeal (Co)
–All spinal nerves exit through intervertebral foramina in
the vertebral column.
Cranial Nerves
•The 12 pairs of cranial nerves are part of the
peripheral nervous system (PNS) and pass through
foramina or fissures in the cranial cavity
•All nerves except one, the accessory nerve [XI],
originate entirely from the brain.
•Have components
•Somatic
•Visceral
•Special sensory and motor components
•The 12 pairs of cranial nerves are part of the
peripheral nervous system (PNS) and pass through
foramina or fissures in the cranial cavity
•All nerves except one, the accessory nerve [XI],
originate entirely from the brain.
•Have components
•Somatic
•Visceral
•Special sensory and motor components
Cranial nerves
•The 12 pairs of cranial nerves are part of the peripheral
nervous system (PNS) and associated with the brain
–All except one, the accessorynerve[XI], originate from the
brain
•They pass through foraminaor fissuresin the cranial
cavity
•The first two attach to the forebrain, while the rest
originate from the brain stem
•Cranial nerves serve only the head and neck structures
with the exceptionof the vagus nerves
•In most cases, the nerve are named for the structures
they serve or their primary functions
•The 12 pairs of cranial nerves are part of the peripheral
nervous system (PNS) and associated with the brain
–All except one, the accessorynerve[XI], originate from the
brain
•They pass through foraminaor fissuresin the cranial
cavity
•The first two attach to the forebrain, while the rest
originate from the brain stem
•Cranial nerves serve only the head and neck structures
with the exceptionof the vagus nerves
•In most cases, the nerve are named for the structures
they serve or their primary functions
Cranial Nerves
•The cranial nerves are
numbered from the most
rostralto the most caudal
•Some cranial nerves are
exclusively sensoryand
others are exclusively
motorand still others are
mixed
Motoronly –CN III, IV,
VI, XI, XII
Sensoryonly –CN I, II, VIII
Mixed–CN V, VII, IX & X
•The cranial nerves are
numbered from the most
rostralto the most caudal
•Some cranial nerves are
exclusively sensoryand
others are exclusively
motorand still others are
mixed
Motoronly –CN III, IV,
VI, XI, XII
Sensoryonly –CN I, II, VIII
Mixed–CN V, VII, IX & X
Origin of cranial
nerves
nerves
Olfactory CN I
•Fibers arise from
olfactory
epithelium of nasal
cavity
•12-20 olfactory
nerve fibers pass
through cribriform
plateof ethmoid
into the anterior
cranial fossa
•Synapse with olfactory bulb
which extends as olfactory tract
•Purely sensory; carries afferent
impulses for sense of smell
•Anosmia–loss of the sense of
•Fibers arise from
olfactory
epithelium of nasal
cavity
•12-20 olfactory
nerve fibers pass
through cribriform
plateof ethmoid
into the anterior
cranial fossa
•Synapse with olfactory bulb
which extends as olfactory tract
•Purely sensory; carries afferent
impulses for sense of smell
•Anosmia–loss of the sense of
Optic Nerve: CN II
Origin -ganglion cells of the
retina
•Part of the brain
developmentally, has
meninges
Course–three parts
Orbit → Optic canal
→ Cranial cavity
•Converge to form optic
chiasma with partial
crossover
•Enter thalamusand
synapse; thalamic fibers
runs as optic radiation to
visual cortex for
interpretation
nucleus of thalamus
Origin -ganglion cells of the
retina
•Part of the brain
developmentally, has
meninges
Course–three parts
Orbit → Optic canal
→ Cranial cavity
•Converge to form optic
chiasma with partial
crossover
•Enter thalamusand
synapse; thalamic fibers
runs as optic radiation to
visual cortex for
interpretation
nucleus of thalamus
•Fibers extend from
midbrainto the eye
•Purely motor and contain
parasymp.fibers arising
from Edinger Westephal
nuclei to sphincter
pupilae & ciliary muscles
•Supplies four(superior, inferior, medial recus and
inferior oblique) of six extrinsic muscles + lavator
palpabrae that move the eye ball
•In the cavernous sinus-two divisions
Superior
Inferior
•Leave the cranial cavity through superior orbital
Oculomotor Nerve: CN III
midbrainto the eye
•Purely motor and contain
parasymp.fibers arising
from Edinger Westephal
nuclei to sphincter
pupilae & ciliary muscles
•Supplies four(superior, inferior, medial recus and
inferior oblique) of six extrinsic muscles + lavator
palpabrae that move the eye ball
•In the cavernous sinus-two divisions
Superior
Inferior
•Leave the cranial cavity through superior orbital
Oculomotor Nerve: CN III
Trochlear Nerves: CN IV
•Fibers emerge
from midbrainto
enter orbits
through superior
orbital fissure
•Purely motor
Innervates
superior
oblique muscle
Midbrain
•Fibers emerge
from midbrainto
enter orbits
through superior
orbital fissure
•Purely motor
Innervates
superior
oblique muscle
Midbrain
Trigeminal Nerves: CN V
•Extends from pons to face, Mixed nereve
The sensory root-trigeminal ganglion
•Forms three divisions
–Ophthalmic–superior orbital fissureinto the orbit,
purely sensory
–Maxillary-foramen rotundumto pterygopalatine
fossa, purely sensory
–Mandibular–foramen ovaleto infratemporal fossa,
mixed
•Sensory-to the face, forehead, tongue, palate& cheek
•Motor-to the muscle of mastication
•Extends from pons to face, Mixed nereve
The sensory root-trigeminal ganglion
•Forms three divisions
–Ophthalmic–superior orbital fissureinto the orbit,
purely sensory
–Maxillary-foramen rotundumto pterygopalatine
fossa, purely sensory
–Mandibular–foramen ovaleto infratemporal fossa,
mixed
•Sensory-to the face, forehead, tongue, palate& cheek
•Motor-to the muscle of mastication
Abducent Nerves: CN VI
•Fibers leave
inferior pons
and enter orbit
through
superior orbital
fissure
•Purely motor
•Supply the
lateral rectus
•Fibers leave
inferior pons
and enter orbit
through
superior orbital
fissure
•Purely motor
•Supply the
lateral rectus
Facial Nerves: CN VII
•Fibers issue from the pons, enter into the inner ear through
internal acoustic meatus
•Leave the tympanic cavity through stylomastoid foramen,
•Mixed nerve
Sensory root -geniculate ganglion in internal acoustic
meatus
Special sense to anterior 2/3 of tongue
Parasympathetic fibers, secretomotor to
submandibular & sublingual salivary glands & to the
pterygopalatine ganglion ( lacrimal, oral cavity, nasal C)
•Fibers issue from the pons, enter into the inner ear through
internal acoustic meatus
•Leave the tympanic cavity through stylomastoid foramen,
•Mixed nerve
Sensory root -geniculate ganglion in internal acoustic
meatus
Special sense to anterior 2/3 of tongue
Parasympathetic fibers, secretomotor to
submandibular & sublingual salivary glands & to the
pterygopalatine ganglion ( lacrimal, oral cavity, nasal C)
Vestibulocochlear Nerves: CN VIII
•Purely
sensory
•This nerve
provides
hearing and
balance
•Fibers arise from
spiral ganglion &
vestibular ganglion
of the inner ear
•Enter cranial cavity
through internal
acoustic meatus
•Finally to the brain
stem at pons -
medulla border
•Purely
sensory
•This nerve
provides
hearing and
balance
•Fibers arise from
spiral ganglion &
vestibular ganglion
of the inner ear
•Enter cranial cavity
through internal
acoustic meatus
•Finally to the brain
stem at pons -
medulla border
Glossopharyngeal CN IX
•Fibers emerge
frommedullaand
leave the cranial
cavity through
jugular foramen
and join the neck
region
•Enter the pharynx
between the
superior & middle
constrictors
Mixednerve
•Motor fibers-pharynx
•Sensory fibers -taste and general from the
posterior 1/3 of the tongue and pharynx
•Parasympathetic fibers-through lesser
petrosal to the parotid gland
•Fibers emerge
frommedullaand
leave the cranial
cavity through
jugular foramen
and join the neck
region
•Enter the pharynx
between the
superior & middle
constrictors
Mixednerve
•Motor fibers-pharynx
•Sensory fibers -taste and general from the
posterior 1/3 of the tongue and pharynx
•Parasympathetic fibers-through lesser
petrosal to the parotid gland
Vagus CN X
–Motor fibers –to striated,
smooth & muscles of pharynx
larynx, respiratory and GIT
tract and to myocardium
Parasympathetic fibers–
glands of respiratory and
alimentary tracts
–Taste fibers from the epiglottis
& root the tongue
–General sense (superior and
inferior vagal ganglia) –
carotid, external acoustic
meatus, tympanic membrane,
respiratory & alimentary tracts
–Other branches–meningeal,
auricular
•Mixedand originates from medulla →
jugular foramen
–Motor fibers –to striated,
smooth & muscles of pharynx
larynx, respiratory and GIT
tract and to myocardium
Parasympathetic fibers–
glands of respiratory and
alimentary tracts
–Taste fibers from the epiglottis
& root the tongue
–General sense (superior and
inferior vagal ganglia) –
carotid, external acoustic
meatus, tympanic membrane,
respiratory & alimentary tracts
–Other branches–meningeal,
auricular
•Mixedand originates from medulla →
jugular foramen
Accessory CN XI
–Cranial root–medulla, join
the spinal root in the cranial
cavity but the two roots
separate after passing through
Jugular and joins the vagus
–Spinal roots–5(C
1-5)
segmentswhich untimely fuse
and enter the cranial cavity
through foramen magnum and
join the cranial root
•Purely motor originating by two roots →
jugular foramen
Functions
•Cranial root –motor to muscles of palate, pharynx and
larynx
•Spinal root-sternocleidomastoid & trapezius
–Cranial root–medulla, join
the spinal root in the cranial
cavity but the two roots
separate after passing through
Jugular and joins the vagus
–Spinal roots–5(C
1-5)
segmentswhich untimely fuse
and enter the cranial cavity
through foramen magnum and
join the cranial root
•Purely motor originating by two roots →
jugular foramen
Functions
•Cranial root –motor to muscles of palate, pharynx and
larynx
•Spinal root-sternocleidomastoid & trapezius
Hypoglossal CN XII
•Purely motor
•Originating
from the
medulla
oblongata
•Leave the
cranial cavity
through
hypoglossal
canal
•Supply intrinsicand extrinsic muscles of
the tongueexcept Palatoglossus
•Purely motor
•Originating
from the
medulla
oblongata
•Leave the
cranial cavity
through
hypoglossal
canal
•Supply intrinsicand extrinsic muscles of
the tongueexcept Palatoglossus
Cranial nerve …
•In human embryology, six pharyngeal arches are
designated, but the fifthpharyngeal arch never develops
•Each of the pharyngeal arches that does develop is
associated with a developing cranial nerve or one of its
branches
–These cranial nerves carry efferent fibers that innervate the
musculaturederived from the pharyngeal arch
•Innervation of the musculature derived from the five
pharyngeal arches that do develop is as follows:
First arch-trigeminal nerve [V
3]
Second arch-facial nerve [VII]
Third arch-gloss pharyngeal nerve [IX]
Fourth arch-superior laryngeal branch of the vagus nerve [X]
Sixth arch-recurrent laryngeal branch of the vagus nerve [X]
•In human embryology, six pharyngeal arches are
designated, but the fifthpharyngeal arch never develops
•Each of the pharyngeal arches that does develop is
associated with a developing cranial nerve or one of its
branches
–These cranial nerves carry efferent fibers that innervate the
musculaturederived from the pharyngeal arch
•Innervation of the musculature derived from the five
pharyngeal arches that do develop is as follows:
First arch-trigeminal nerve [V
3]
Second arch-facial nerve [VII]
Third arch-gloss pharyngeal nerve [IX]
Fourth arch-superior laryngeal branch of the vagus nerve [X]
Sixth arch-recurrent laryngeal branch of the vagus nerve [X]
Nerve Exit from skull
Olfactory [I] Cribriform plate of ethmoid bone
Optic [II] Optic canal
Oculomotor [III] Superior orbital fissure
Trochlear [IV] Superior orbital fissure
Trigeminal [V] Sup. orbital fissure-ophthalmic [V
1]
Foramen rotundum-maxillary [V
2]
Foramen ovale-mandibular [V
3]
Abducent [VI] Superior orbital fissure
Facial [VII] Internal acoustic meatus
Vestibulocochlear [VIII]Internal acoustic meatus
Glossopharyngeal [IX]*Jugular foramen
Vagus [X]* Jugular foramen
Accessory [XI] Jugular foramen
Hypoglossal [XII] Hypoglossal canal
Olfactory [I] Cribriform plate of ethmoid bone
Optic [II] Optic canal
Oculomotor [III] Superior orbital fissure
Trochlear [IV] Superior orbital fissure
Trigeminal [V] Sup. orbital fissure-ophthalmic [V
1]
Foramen rotundum-maxillary [V
2]
Foramen ovale-mandibular [V
3]
Abducent [VI] Superior orbital fissure
Facial [VII] Internal acoustic meatus
Vestibulocochlear [VIII]Internal acoustic meatus
Glossopharyngeal [IX]*Jugular foramen
Vagus [X]* Jugular foramen
Accessory [XI] Jugular foramen
Hypoglossal [XII] Hypoglossal canal
Spinal Nerves
•There are 31 pairs of spinal
nerves each containing
thousands of nerve fibers
•All arise from the spinal cord
and supply all parts of the body
except the head and neck
•All are mixed nerves
•Spinal nerves are named
according to where they exit
the spinal cord
•There are 31 pairs of spinal
nerves each containing
thousands of nerve fibers
•All arise from the spinal cord
and supply all parts of the body
except the head and neck
•All are mixed nerves
•Spinal nerves are named
according to where they exit
the spinal cord
Distribution of Spinal Nerves
•The distribution of spinal
nerves
–Cervical (8)
–Thoracic (12)
–Lumbar (5)
–Sacral (5)
–Coccyx (1)
•Note that C1 has nerves
that exit superior and
inferior to the vertebrae
to add to the total of 8
cervical nerves
•The distribution of spinal
nerves
–Cervical (8)
–Thoracic (12)
–Lumbar (5)
–Sacral (5)
–Coccyx (1)
•Note that C1 has nerves
that exit superior and
inferior to the vertebrae
to add to the total of 8
cervical nerves
Innervation of Body Regions
•Except for T2-T12, all
ventral rami branch and
join one another lateral
to the vertebral column
forming nerve plexuses
–Cervical
–Brachial
–Lumbar
–Sacral
•Note that only ventral
roots form plexuses
•Except for T2-T12, all
ventral rami branch and
join one another lateral
to the vertebral column
forming nerve plexuses
–Cervical
–Brachial
–Lumbar
–Sacral
•Note that only ventral
roots form plexuses
Cervical Plexus and the Neck
•The cervical plexus
lies deep under the
sternocleidomastoid
muscle
•Plexus is formed by
the ventral rami of
the first 4 cervical
nerves
•Most branches are
cutaneous nerve
that transmit
sensory impulses
from the skin
•The cervical plexus
lies deep under the
sternocleidomastoid
muscle
•Plexus is formed by
the ventral rami of
the first 4 cervical
nerves
•Most branches are
cutaneous nerve
that transmit
sensory impulses
from the skin
Cervical Plexus and the Neck
•The single most
important nerve of
the plexus is the
phrenic nerve
•It receives its fibers
from C3 -C4
•The phrenic nerve
runs inferiorly
through the thorax
and supplies motor
and sensory fibers to
diaphragm
•Breathing
•The single most
important nerve of
the plexus is the
phrenic nerve
•It receives its fibers
from C3 -C4
•The phrenic nerve
runs inferiorly
through the thorax
and supplies motor
and sensory fibers to
diaphragm
•Breathing
Brachial Plexus and Upper Limb
•The plexus is formed by the intermixing of the ventral
rami of the four inferior cervical nerves C5-C8 and most
of T1
•It often receives fibers from C4 or T2
•The plexus is formed by the intermixing of the ventral
rami of the four inferior cervical nerves C5-C8 and most
of T1
•It often receives fibers from C4 or T2
Brachial Plexus and Upper Limb
•A summary of the differentiation of the brachial plexus
reveals how it gives rise to common nerves
•The five peripheral nerves that emerge are the main
nerves of the upper limb
•A summary of the differentiation of the brachial plexus
reveals how it gives rise to common nerves
•The five peripheral nerves that emerge are the main
nerves of the upper limb
Brachial Plexus and Upper Limb
•The main nerves that
emerge from the brachial
plexus are
Axillary
–It runs posterior to the surgical
neck of the humerous
–innervates the deltoidand teres
minor musclesand the skin and
joint of the shoulder
Musculocutaneous
•Muscular branches
–Biceps brachii
–Brachialis
–Coracobrachialis
•Cutaneous branches
–Cutaneous sensation of
anterolateral forearm
Roots
•The main nerves that
emerge from the brachial
plexus are
Axillary
–It runs posterior to the surgical
neck of the humerous
–innervates the deltoidand teres
minor musclesand the skin and
joint of the shoulder
Musculocutaneous
•Muscular branches
–Biceps brachii
–Brachialis
–Coracobrachialis
•Cutaneous branches
–Cutaneous sensation of
anterolateral forearm
Roots
Median Nerve
•The median nerve descends through the arm without branching
•In the anterior forearm, it gives off branches to the skin and most
of the flexor muscles
•It innervates the five intrinsic muscles of the lateral palm
Muscular branches
•Palmaris longus
•Flexor Carpi radials
•Flexor digitorium
superficialis
•Flexor pollicus longus
•Flexor digitorium
profundus
•Pronator
•Intrinsic muscles of fingers
2 & 3
Cutaneous branches
•Skin of lateral two-thirds
•The median nerve descends through the arm without branching
•In the anterior forearm, it gives off branches to the skin and most
of the flexor muscles
•It innervates the five intrinsic muscles of the lateral palm
Muscular branches
•Palmaris longus
•Flexor Carpi radials
•Flexor digitorium
superficialis
•Flexor pollicus longus
•Flexor digitorium
profundus
•Pronator
•Intrinsic muscles of fingers
2 & 3
Cutaneous branches
•Skin of lateral two-thirds
Ulnar Nerve
•The ulnar nerve branches off
the medial cord of the
plexus
•It descends along the medial
aspect of the arm toward
the elbow, swings behind
the medial epicondyle, then
follows the ulna along the
forearm
•Innervates most intrinsic
hand muscles
Muscular branches
Flexor Carpi ulnaris
Flexor digitorium
profundus (medial
half)
Intrinsic muscles of
the hand
•The ulnar nerve branches off
the medial cord of the
plexus
•It descends along the medial
aspect of the arm toward
the elbow, swings behind
the medial epicondyle, then
follows the ulna along the
forearm
•Innervates most intrinsic
hand muscles
Muscular branches
Flexor Carpi ulnaris
Flexor digitorium
profundus (medial
half)
Intrinsic muscles of
the hand
Radial Nerve
•The radial nerve is a continuation of the posterior cord
•The nerve wraps around humerous, runs anteriorly by the lateral
epicondyle at the elbow
•Divides into a super-ficial branch that follows the radius and a deep
branch that runs posteriorly
Muscular branches
Triceps brachii
Anconeus
Supinator
Brachioradialis
Extensor capri radialis
Extensor carpi brevis
Extensor carpi ulnaris
Muscles that extend fingers
Cutaneous branches
Skin of posterior surface of
entire limb
•The radial nerve is a continuation of the posterior cord
•The nerve wraps around humerous, runs anteriorly by the lateral
epicondyle at the elbow
•Divides into a super-ficial branch that follows the radius and a deep
branch that runs posteriorly
Muscular branches
Triceps brachii
Anconeus
Supinator
Brachioradialis
Extensor capri radialis
Extensor carpi brevis
Extensor carpi ulnaris
Muscles that extend fingers
Cutaneous branches
Skin of posterior surface of
entire limb
Lumbar Plexus and Lower Limb
•The lumbar plexus arises
from the first four spinal
nerves and lies within the
psoas major muscle
•Its proximal branches
innervate parts of the
abdominal wall and
iliopsoas
•Major branches of the
plexus descend to innervate
the medial and anterior
thigh
Lumbosacral Plexus
•The sacral and lumbar plexuses overlap substantially
•The lumbar plexus arises
from the first four spinal
nerves and lies within the
psoas major muscle
•Its proximal branches
innervate parts of the
abdominal wall and
iliopsoas
•Major branches of the
plexus descend to innervate
the medial and anterior
thigh
Lumbosacral Plexus
•The sacral and lumbar plexuses overlap substantially
Femoral Nerve
•The femoral nerve, the largest of the
lumbar plexus, runs deep to the inguinal
ligament to enter the thigh and then
divides into a number of large branches
•The motor branches innervate the anterior
thigh muscles while the cutaneous branch
serves anterior thigh
Muscular branch
Quadriceps group
Rectus femoris, vastus
laterialis, vastus medialis,
vastus intermedius
Sartorius
Pectineus
Iliacus
Cutaneous branches
Anterior femoral cutaneous
Skin of anterior and medial
•The femoral nerve, the largest of the
lumbar plexus, runs deep to the inguinal
ligament to enter the thigh and then
divides into a number of large branches
•The motor branches innervate the anterior
thigh muscles while the cutaneous branch
serves anterior thigh
Muscular branch
Quadriceps group
Rectus femoris, vastus
laterialis, vastus medialis,
vastus intermedius
Sartorius
Pectineus
Iliacus
Cutaneous branches
Anterior femoral cutaneous
Skin of anterior and medial
Obturator Nerve
•The obturator nerve enters
the medial thigh via the
obturator foramen and
innervates the adductor
muscles
Muscular branch
Adductor magnus (part)
Adductor longus
Adductor brevis
Gracilis
Obturator externus
Cutaneous branches
Sensory for skin of
medial thigh and hip and
knee joints
•The obturator nerve enters
the medial thigh via the
obturator foramen and
innervates the adductor
muscles
Muscular branch
Adductor magnus (part)
Adductor longus
Adductor brevis
Gracilis
Obturator externus
Cutaneous branches
Sensory for skin of
medial thigh and hip and
knee joints
Sacral Plexus and Lower Limb
•Half the nerves serve muscles of the buttocks and lower
limb while others innervate pelvic structures and the
perineum
•Half the nerves serve muscles of the buttocks and lower
limb while others innervate pelvic structures and the
perineum
Sciatic Nerve
•The sciatic nerve is the thickest and
longest nerve in the body
•The sciatic nerve leaves the pelvis via the
greater sciatic notch
•Actually the tibial and common peroneal
nerves
•It courses deep to the gluteus maximus
muscle
•It gives off branches to the hamstrings
and adductor magnus
Muscular branch
Bicep femoris
Semitendinous
Semimembranous
Adductor magnus
Cutaneous branches
Posterior thigh
•The sciatic nerve is the thickest and
longest nerve in the body
•The sciatic nerve leaves the pelvis via the
greater sciatic notch
•Actually the tibial and common peroneal
nerves
•It courses deep to the gluteus maximus
muscle
•It gives off branches to the hamstrings
and adductor magnus
Muscular branch
Bicep femoris
Semitendinous
Semimembranous
Adductor magnus
Cutaneous branches
Posterior thigh
Tibial Nerve
•The tibial nerve through the popliteal
fossa and supplies the posterior
compartment muscles of the leg and the
skin of the posterior calf and sole of foot
•Important branches of the tibial nerve
are the sural, which serves the skin of
the posterior leg and the plantar nerves
which serve the foot
Muscular branch
Tibialis posterior
Popliteus
Flexor digitorum longus
Flexor hallicus longus
Intrinsic muscle of the foot
Cutaneous branches
Skin of the posterior surface of the
leg and the sole of the foot
•The tibial nerve through the popliteal
fossa and supplies the posterior
compartment muscles of the leg and the
skin of the posterior calf and sole of foot
•Important branches of the tibial nerve
are the sural, which serves the skin of
the posterior leg and the plantar nerves
which serve the foot
Muscular branch
Tibialis posterior
Popliteus
Flexor digitorum longus
Flexor hallicus longus
Intrinsic muscle of the foot
Cutaneous branches
Skin of the posterior surface of the
leg and the sole of the foot
Common Peroneal Nerve
•The common peroneal nerve
descends the leg, wraps around the
head of the fibula, and then divides
into superficial and deep branches
•These branches innervate the knee
joint, the skin of the lateral calf and
dorsum of the foot and the muscles
of the anterolateral leg
•Muscular branch
–Biceps foemoris (short head)
–Peroneal muscles (longus, brevis, tertius)
–Tibialis anterior
–Extensor hallicus longus
–Extensor digitorum longus
–Extensor digitorum brevis
•Cutaneous branches
–Skin of the anterior surface of leg and
dorsum of foot
•The common peroneal nerve
descends the leg, wraps around the
head of the fibula, and then divides
into superficial and deep branches
•These branches innervate the knee
joint, the skin of the lateral calf and
dorsum of the foot and the muscles
of the anterolateral leg
•Muscular branch
–Biceps foemoris (short head)
–Peroneal muscles (longus, brevis, tertius)
–Tibialis anterior
–Extensor hallicus longus
–Extensor digitorum longus
–Extensor digitorum brevis
•Cutaneous branches
–Skin of the anterior surface of leg and
dorsum of foot
Sarcal Plexus Nerves …
•Superior and inferior gluteal
–Innervate the gluteal muscles and
tensor fasciae latae
•Pudendal
–Innervates the muscles of the skin
of the perineum
–Mediates the act of erection
–Voluntary control of urination
–External anal sphinter
•Superior and inferior gluteal
–Innervate the gluteal muscles and
tensor fasciae latae
•Pudendal
–Innervates the muscles of the skin
of the perineum
–Mediates the act of erection
–Voluntary control of urination
–External anal sphinter
Innervation of Skin: Dermatomes
•The skin that is
innervated by the
cutaneous branch of a
spinal nerve is called a
dermatome
•All spinal nerves except
C1 participate in
dermatomes
•Adjacent dermatomes
on the body trunk are
fairly uniform in width,
almost horizontal, and
in direct line with their
spinal nerves
•The skin of the upper limbs is supplied by C5-T1
•The ventral rami of the lumbar nerves supply most of the ant.
muscles of the thighs and legs
•The ventral rami of sacral nerves serve most of the post. surfaces of
the lower limbs
•The skin that is
innervated by the
cutaneous branch of a
spinal nerve is called a
dermatome
•All spinal nerves except
C1 participate in
dermatomes
•Adjacent dermatomes
on the body trunk are
fairly uniform in width,
almost horizontal, and
in direct line with their
spinal nerves
•The skin of the upper limbs is supplied by C5-T1
•The ventral rami of the lumbar nerves supply most of the ant.
muscles of the thighs and legs
•The ventral rami of sacral nerves serve most of the post. surfaces of
the lower limbs
Autonomic Nervous System
•visceral afferent (sensory)
–In their role as the afferent component of autonomic reflexes and
in conducting visceral pain impulses
–Visceral afferent (sensory) fibers also regulate visceral function
•Visceral efferent(motor)
–Fibers of this system are accompanied by visceral afferent (sensory)
fibers
–The visceral efferent (motor) fibers innervate
Involuntary (smooth) muscles
In the walls of organs and blood vessels
Cardiac muscle
Glands
Functional division
…
•visceral afferent (sensory)
–In their role as the afferent component of autonomic reflexes and
in conducting visceral pain impulses
–Visceral afferent (sensory) fibers also regulate visceral function
•Visceral efferent(motor)
–Fibers of this system are accompanied by visceral afferent (sensory)
fibers
–The visceral efferent (motor) fibers innervate
Involuntary (smooth) muscles
In the walls of organs and blood vessels
Cardiac muscle
Glands
Functional division
…
Autonomic Nervous System …
•The efferent nerve fibers and
ganglia of the ANS are organized
into two systems or divisions:
–Sympathetic(thoracolumbar)
division. In general, the effects of
sympathetic stimulation are catabolic
(preparing the body to flight or fight).
–Parasympathetic(craniosacral)
division. In general, the effects of
parasympathetic stimulation are
anabolic (promoting normal function
and conserving energy).
•Although both sympathetic and
parasympathetic systems innervate the
same structures, they have different
(usually contrasting) but coordinated
effects
•The efferent nerve fibers and
ganglia of the ANS are organized
into two systems or divisions:
–Sympathetic(thoracolumbar)
division. In general, the effects of
sympathetic stimulation are catabolic
(preparing the body to flight or fight).
–Parasympathetic(craniosacral)
division. In general, the effects of
parasympathetic stimulation are
anabolic (promoting normal function
and conserving energy).
•Although both sympathetic and
parasympathetic systems innervate the
same structures, they have different
(usually contrasting) but coordinated
effects
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