Comprehensive Overview of the Nervous System and Its Functions

This PowerPoint presentation provides an in-depth exploration of the nervous system, covering its structure, function, and the intricate network that coordinates bodily activities. Key topics include the central and peripheral nervous systems, neuron anatomy, synaptic transmission, and the role of neurotransmitters. Additionally, the presentation discusses common neurological disorders and their implications for health. This resource is ideal for students, healthcare professionals, and anyone interested in understanding the complexities of the nervous system.

1. Physiology of Nervous
S
ystem
1
Spinal
Cord
Brain
Nerves

2. 2
Organization of the NS…cont’d

3. Organization of the NS cont’d….
3

4. 4
Organization of the Nervous System …cont’d
Peripheral Nervous System -PNS
•The nervous system outside of the brain and spinal cord
•Consists of:
•-31 pairs of Spinal nerves
(8 pairs of cervical nerves (C1-C8),12 pairs of thoracic nerves (T1 –
T12),5 pairs of lumbar nerves (L1-L5),5 pairs of sacral nerves (S1-
S5),1 pair of coccygeal nerves (Co1))
-Carry info to and from the spinal cord
-12 pairs of Cranial nerves

5. 5
 Cranial
Nerve
 Name Sensory Motor
 Autonomic
Parasympathetic
 I OlfactorySmell   
 II Optic vision 
 IIIOculomotor
 
Proprioception
 
 
4 Extrinsic Eye
muscles
Pupillary
constriction
Accommodation
Focusing
 IV Trochlear Proprioception
1 Extrinsic Eye
muscle
(Sup. Oblique)
 
 V Trigeminal
Somatic senses
(Face, tongue)
Chewing  
 VIAbducens Proprioception 
1 Extrinsic Eye
muscle
(Lateral rectus)
 
Cranial nerves (I-VI)

6. 6
 Cranial
Nerve
 Name Sensory Motor
 Autonomic
Parasympathetic
 VII Facial
 Taste
Proprioception
Muscles of facial
expression
Salivary glands
Tear glands
 VIII
 Auditory
(Vestibulo
cochlear)
Hearing.&
Balance
  
 IX
 Glossopharyngeal
 -Taste
-Blood gases
-Blood pressure
Swallowing
Gagging
Salivary glands
 X Vagus
-Blood pressure
-Blood gases
 
-Taste
-Speech
-Swallowing
Gagging
Many visceral
organs
(heart, gut, lungs)
 XI Spinal accessory Proprioception
 
Neck muscles:
Sternocleidomastoid
Trapezius
 
 XII Hypoglossal Proprioception
 
Tongue muscles
Speech
 
Cranial nerves (VII-XII)

7. 7
Cranial Nerves Mediate 5 Special Senses: Smell, Vision, Hearing,
Taste, Equilibrium
•Smell: CN-I (Olfactory)
•Vision: CN- II (Optic)
•Hearing: CN-VIII (Cochlear division)
•Equilibrium: CN-VIII (vestibular division)
•Taste: CNs -VII, IX, X (minor) (Facial, Glossopharyngeal, Vagus)
Cranial nerves …. cont’d

8. Cranial nerves …. cont’d
Several of the Nerves Innervate Skeletal Muscles
•The Facial nerve (VII): controls muscles of facial expression
•The Spinal accessory (XI): stimulates the trapezius and
sternocleidomastoid muscles
•Chewing muscles (masseter, temporalis): are innervated by the
Trigeminal (V)
•Speech muscles (larynx): are under the control of the Vagus (X)
•The Hypoglossal (XII): moves the tongue
9

9. 10
Cranial nerves …. cont’d
Four of the cranial nerves Carry Parasympathetic Fibers
•Oculomotor (III): innervates iris constrictor (causes pupil
constriction); also controls ciliary muscle (focuses the lens)
•Facial (VII) and Glossopharyngeal (IX): stimulate salivary glands to
secrete saliva.
•Vagus (X): the major nerve of the parasympathetic system: goes to
most visceral organs (heart, lungs, kidneys, liver, stomach, intestines)

10. 11
Cranial nerves …. cont’d
Damage to cranial nerves causes many medical problems
•Anosmia (loss of smell): sometimes caused by fractures which damage the
cribiform plate. This damages the Olfactory nerve as it passes through this plate.
•Bell's Palsy: paralysis of the muscles of facial expression on one side. Caused
by inflammation of the Facial nerve.
•Trigeminal neuralgia: severe facial pain caused by inflammation of the
trigeminal nerve.
•Blindness: caused by damage to optic nerve.

11. 12
Comparison of somatic NS vs Autonomic NS
Somatic NS
1.Controls voluntary activities
2.Effector organs - the skeletal
muscle
3.Nerve fibres are originated
from the anterior horn of the
grey matter of the spinal cord
4.The motor nerve (pathway)
contains single neuron to the
effector cell
5.Always excitatory
6.The NT is always
acetylcholine and the
receptor is cholinergic
receptor (nicotinic receptor)
Autonomic NS
1.Controls involuntary activities
2.Effector organs – smooth muscle,
cardiac muscle and glands
3.Nerve fibres are originated from
lateral horn of the spinal cord
4.Autonomic nerves motor
pathway contains two
consecutive neurons
(preganglionic & postganglionic
neurons) to effector cell
5. It can be inhibitory or excitatory
6.The NTs are acetylcholine and
norepinephrine and the receptors
are adrenergic and cholinergic

12. 13

13. 14
Autonomic Nervous System
It is the portion of the nervous system that controls most visceral
functions of the body
This system helps to control:
oarterial pressure
ogastrointestinal motility
ogastrointestinal secretion
ourinary bladder emptying
osweating
obody temperature

14. 15
…cont’d
•Can be divided into:
–Sympathetic Nervous System
– It controls the body's "fight or
flight" responses, or how the body
reacts to perceived danger.
–Parasympathetic Nervous System
•The parasympathetic nervous
system controls the "rest and
digest" functions of the body.
•However, there is often dual
innervation

15. 16
Dual innervation
•Innervation by both PaSN and syNS
•Most body structures receive dual innervations
•Purpose: For better control
•The following structures do not receive dual innervation only
sympathetic and cholinergic:
–The sweat glands
–Adrenal medulla
–Blood vessels of the skeletal muscles
–Skin piloerectors

16. Autonomic innervation

17. 18
Sympathetic Division: (Thoracolumbar out flow)
•Originates in lateral horns of T
1
-T
12
and L
1
-L
2
region of spinal
cord
            
• Components of the Sympathetic neurons
–Cell bodies of preganglionic motor neurons are located in
the thoracic and lumbar part of the spinal cord
–Preganglionic axons synapse in ganglia, which are located
near the spinal cord far away from the organs being
innervated
–Contains short preganglionic neurons which are cholinergic.
–Sympathetic postganglionic axons travel to the target organ
–Contains long postganglionic neurons

18. 19

19. 20
Functions of the Sympathetic NS
•Sympathetic - largely fight or flight response
•Increases metabolic rate
•Increases cardiac output during exercise and excitements
•Generally excitatory to almost all body parts except for the
gastrointestinal tract (GIT).
•Has inhibitory effects on the GIT

20. See effects
21

21. 22
Parasympathetic Division: (Craniosacral)
•Originates from cranial and sacral regions.
•Cranial components are part of CN III (Oculomotor), VII (Facial),
IX (Glossopharyngeal), and X (Vagus)
•Sacral components from S
2 - S
4 segments of the spinal nerves.
Organization of the parasympathetic neurons
1.Cell bodies of preganglionic motor neurons located in parts of certain
nuclei of cranial nerves and in the sacral part of the spinal cord
2.Preganglionic axons synapse in terminal ganglia which are located
close to or on the organ being innervated
3.Contains long preganglionic neurons
4.Parasympathetic postganglionic axons travel from the terminal
ganglia to the target organ
5.Contains short postganglionic cholinergic neurons

22. see
23

23. 24
Function of PsNS
•Regulation of digestion, defecation and micturition
•Conservation of energy, anabolic, maintains a homeostatic
environment
 ”resting and digesting" system
•There is tonic impulse discharge to the heart
•Parasympathetic neurons in general have inhibitory effect on
almost all body tissues except in the GIT. They have excitatory
effects on the GIT.

24. 25
Properties of pre- and post -ganglionic neurons
•All preganglionic neurons are cholinergic neurons.
–They secrete acetylcholine and are excitatory
•Sympathetic post ganglionic neurons are adrenergic with few
exceptions
–They secrete norepinephrine and are either excitatory or
inhibitory.
•Parasympathetic post ganglionic neurons are cholinergic.
–They secrete acetylcholine and are either excitatory or
inhibitory.

25. 26

26. 27
Receptors in the autonomic nervous system
•The receptor on cell membrane is a protein molecule that
penetrates all the way through the cell membrane
•When the neurotransmitter substance binds with the receptor, this
causes a conformational change in the structure of the receptor
protein molecule
1.Acetylcholine Receptors (Cholinergic receptors)
•Two principal receptors of
a.Nicotinic receptors
b.Muscarinic receptors

27. 28
…cont’d
a.Muscarinic receptors
found on all effector cells that are stimulated by the
postganglionic cholinergic neurons of either the PNS or
SNS
b .Nicotinic receptors
activated by nicotine a chemical found in tobacco
are found in the autonomic ganglia at the synapses between
the pre- and postganglionic neurons of both the SNS and
PNS
also found at the NMJs in skeletal muscle (somatic
division)

28. 29
…cont’d
2.Adrenergic receptors
•there are two types of adrenergic receptors: alpha (alpha
1
and
alpha
2)
receptors and beta (beta
1
, beta
2
) receptors
•NE excites mainly alpha receptors but excites the beta receptors
to a lesser extent as well
•epinephrine excites both alpha & beta receptors approximately
equally

29. 30
ANS Neurotransmitters
•Two neurotransmitters are used in the ANS.
– acetylcholine (ACh)
– nor epinephrine (NE)
•Neurotransmitters are released by the presynaptic cell or
preganglionic cells.
•Bind to specific receptors in the postsynaptic cell membrane.
•Binding has either an excitatory or an inhibitory effect on the
effector, depending on the specific receptor.

30. 31
ANS Neurotransmitters…cont’d
•Both preganglionic and postganglionic neurons in the
parasympathetic division release acetylcholine and thus are called
cholinergic.
•The preganglionic axon and a few postganglionic neurons in the
sympathetic division are also cholinergic.
•Most of the postganglionic neurons of the sympathetic
division release norepinephrine and are called adrenergic.

31. 32
Autonomic reflexes
•A reflex is a fast and involuntary response to a stimulus
•A reflex action consists of an action that is signalled to CNS
and a reaction sent by the CNS
•Any reflex is transmitted through a reflex arc
•A reflex arc of any reflex has 5-components
1.A receptor that detects changes and generates AP
2.Afferent (sensory) pathway: conducts AP to CNS
3.Integrating centre (spinal cord, brain stem, hypothalamus,
cerebral cortex.)
4.Efferent (motor) pathway: conducts AP to effectors
5.Effectors organs (cardiac muscles, smooth muscles and
glands): receive feedback and accordingly respond.

32. 33
Autonomic reflexes...cont’d
Representative autonomic reflexes:
•The Baroreceptor reflex: maintaining BP
•The chemoreceptor reflex: the carotid bodies and aortic bodies
monitor blood O
2, CO
2 and pH.
•Defecation reflex: the final act of digestion by w/c faecal matter
eliminate from the body.
•Micturition reflex: causes contraction of the detrusor muscle and
relaxation of the external and internal sphincter to result in
emptying of the bladder.

33. 34
Synapses
-A synapse is the tiny gap across which a nerve cell, or neuron, can
send an impulse to another neuron or muscles
-The junction between two cells in which one must be a neuron.
presynaptic neuron (pre-before) refers to a nerve cell that carries a nerve
impulse toward a synapse
a postsynaptic neuron (post-after) is a neuron that carries a nerve impulse
away from a synapse
There are 3 types of synapses
1. Neuroneuronal junction -the junction b/n two neuron.
Presynaptic neuron and postsynaptic neuron
2. Neuromuscular junction - the junction occurred between
neuron & muscle.
3. Neuroglandualr junction-the junction occurred between
neuron & gland

34. Synapsis … cont’d
•There are 3 types of
neuroneuronal junctions

1.1 Axo-dendritic junctions

1.2 Axo-somatic junctions
1.3 Axo-axonic junctions

35. 36
Synaptic Transmission
Two modes of transmission
1. Electrical transmission
2. Chemical transmission
 One neuron will transmit impulse to another
neuron or to a muscle or gland cell by releasing
chemicals called neurotransmitters.

36. Electrical synapses
 in an electrical synapse, two neurons are
connected by gap junctions, which allow
charge-carrying ions to flow directly
between the two cells in either direction
 electrical synapses are relatively rare in
the human nervous system
 gap junctions are more numerous in
smooth muscle and cardiac muscle cells.
37
Electr ical Synapses: Anat omy

37. 38
Chemical Synapses
•Chemical messenger (neurotransmitter) is released from a neuron into the
synaptic cleft.
•Neurotransmitter in the synaptic cleft binds to a receptor on the target cell.
•Acts slower than electrical synapses because the neurotransmitter must
diffuse across the synaptic cleft to bind the receptor.

38. 39
Synapse……
1.Presynaptic terminal
contains neurotransmitter (NT)
2.Synaptic cleft
contains ECF and Enzymes
3.Postsynaptic neuron
contains receptor for the action
of NT

39. 40
Mechanism of Chemical Synaptic Transmission…cont’d
•When the NT-R combination
triggers the opening of ligand
gated Na-channels, this leads to
membrane depolarization,
EPSP.
e.g. Ach on Nicotinic receptor
•When the NT-R combination
triggers the opening of ligand
gated K or Cl-channels, this
leads to membrane
hyperpolarization, IPSP.
e.g. GABA on GABA
b receptor

40. 41
Excitatory Synapses
•Depolarizes postsynaptic cell
–Causes depolarization because of the stronger
force of Na to flow into the cell.
•Depolarization = EPSP (excitatory
postsynaptic potential)

41. 42
•Neurotransmitter binds to receptor,
channels for either K or Cl open
 hyperpolarizes the cell
•If K channels open
– K
+
moves out of the cell IPSP
(inhibitory postsynaptic potential)
•If Cl channels open,
– Cl
-
moves in IPSP

Inhibitory Synapses

42. 43
The Central nervous system
The nervous system is one of the two
regulatory systems in the human body
The CNS contains more than 100
billion neurons.
Consists of:-Brain and Spinal cord.
The Function of CNS:
 Receives input from sensory
neurons.
 Directs activity of motor neurons.
 Association neurons (interneurons)
maintain homeostasis in the internal
environmentenvironment

43. 44
Spinal cord
•Extends from foramen magnum – 2
nd
lumbar vertebra
•Has central grey H-shaped portion & peripheral white
portion.
•Close to spinal cord, sensory and motor nerve fibers
separate into dorsal and ventral root.
•Spinal nerves are 31 pairs:
8 … Cervical
12 … Thoracic
5 … Lumbar
5 … Sacral
1 … Coccygeal (coccyx)

44. 45
The Spinal Cord
The spinal cord has two functions:
1.Common passageway for ascending
and descending tracts.
2. Center for reflexes
-Integrate incoming sensory
information & respond with motor
impulses that control muscles or
glands.
-Reflex -Fast & involuntary
response to a stimulus that doesn’t
involve conscious thought.

45. The Brain
Microscopically, the CNS contains 2
neural elements:
–Neuron cell bodies (clusters are
known as nuclei)
–Nerve fibers (axons) in bundles
called tracts.
Viewed macroscopically, CNS tissues
can be distinguished by color:
–Gray matter consists of somata,
dendrites and unmyelinated axons.
–White matter consists primarily of
myelinated axons.
46

46. Brain Regions
1.Cerebrum
2.Basal ganglia
3.Diencephalon
Thalamus
Hypothalamus
4. Brainstem
Midbrain
Pons
Medulla ob.
5. Cerebellum
Cerebellum
47

47. Cerebrum
•Largest portion of the brain (80% by mass).
•Responsible for higher mental functions
concerning:
–Perception of fine sensation
–Learning, memory, speech
–Judgment
–Planning
•Corpus callosum:
–Major tract of axons that functionally
interconnects right & left cerebral hemispheres.
48

48. Cerebrum:-Cerebrum has 3 functional areas
Sensory areas are involved in the perception of sensory
information
motor areas control the execution of voluntary movements,
and
association areas deal with more complex integrative functions
such as memory, personality traits, and intelligence.
49

49. 50
Cerebral Cortex
3 types of functional areas:
1.Motor
- control voluntary motor
functions.
2.Sensory
- allow for conscious
recognition of stimuli.
3.Association
- integration.
M
S
A

50. Cerebral cortex …
•Each hemisphere contains 4 lobes:
–frontal, parietal, occipital & temporal.
•Has an outer cortex of gray matter
surrounding an interior that is mostly white
matter, except for a few small portions.
•The surface is marked by ridges called gyrus
separated by grooves called sulcus.
–Each gyrus contains one or more functional areas
called Brodmann´s areas.
51

51. Brodmann´s areas of cerebral cortex
52

52. Medulla oblongata
Contains sensory (ascending) tracts
and motor (descending) tracts.
Reticular formation (also in pons,
midbrain, and diencephalon) functions
in consciousness and arousal.
Vital centers regulate heartbeat,
breathing (together with pons), and
blood vessel diameter.
Other centers coordinate swallowing,
vomiting, coughing, and sneezing
Medulla oblongata

53. Pons and Midbrain
Pons: Contains sensory tracts and motor
tracts.
Together with the medulla, helps control
breathing.
Midbrain: Contains sensory tracts and motor
tracts.
Superior colliculi coordinate movements of
head, eyes, and trunk in response to visual
stimuli.
Inferior colliculi coordinate response to
auditory stimuli.
The substantia nigra and red nucleus
contribute to control of movement.
Midbrain
Pons

54. Thalamus, Hypothalamus
Thalamus: Relays almost all
sensory input to the cerebral cortex.
Contributes to motor functions by
transmitting information from the
cerebellum and basal ganglia to
motor areas of the cerebral cortex.
Also plays a role in maintaining
consciousness. Hypothalamus
Thalamus

55. Hypothalamus
•Part of the diencephalons,
•Located near the bottom of
the brain (below thalamus).
•Represents <1% of the brain mass, about 5 gm.
–regardless of its size, it plays most important role in
controlling homeostasis.
–it is the main brain structure involved in regulating
hormonal levels in the body.
56

56. 57
Function of Hypothalamus
1. Controls the ANS
•Anterior nuclei acts as a parasympathetic center.
•Posterior nuclei acts as a sympathetic center.
2.Endocrine function
- Controls:
•Adenohypophyseal hormones.
•Neurohypophyseal hormones.
•Adrenal medulla.

57. Function of Hypothalamus…
3. Regulation of body temperature
•Heat losing center (anterior HT)
•Heat gaining center (posterior HT)
•Thermostat center (anterior preoptic area)
4. Controls food intake (hunger sensation):
- Feeding center (lateral HT)
- Satiety center (ventromedial HT)
5. Control of water-electrolyte balance
- Thirst center (lateral HT)
- Osmoreceptors (anterior HT)
58

58. Language Areas
59
Wernicke’s area
 understanding oral
& written words.
Broca’s area
 speech production.

59. 60
Language areas …
 Broca’s area (area 44,45)
–Involves articulation of speech.
–In damage, unable to speak (aphasia) but
comprehension of speech is unimpaired.
 Wernicke’s area (area 39)
–Involves language comprehension.
–In damage, language comprehension is destroyed and
speech is rapid without any meaning.

60. Language areas …
•Damage to Wernicke's area loss of the ability to
understand language
–person can speak clearly, but the words that are put
together make no sense.
–This way of speaking has been called "word salad" because
it appears that the words are all mixed up like the vegetables
in a salad
•Damage to Broca's Area
–person can understand language words but he can't
properly formed speech or slurred speech.
61

61. Language areas …
Angular gyrus:
Allows us to associate multiple types of language-related
information whether auditory, visual or sensory
If we want speak object to see or the word we heard the brain
transfer this information from first site of perception to angular
gyrus for integration then wenick’s area
–Damage produces aphasias.
62

62. Language areas …

 Arcuate fasciculus (neural pathway)
Nerve fiber that connect language areas
–To speak intelligibly, words originating in Wernicke’s
area must be sent to Broca’s area.
–Broca’s area sends fibers to the motor cortex which
directly controls the musculature of speech.
63

63. 64
Language areas …

64. 65
Lateralization
•The fact that certain activities
are almost exclusively dominant
on 1 of the 2 hemispheres.
–In most people, the left hemisphere has a more
control over language, math, & logic.
–While the right hemisphere is geared towards
musical, artistic activities
•Most individuals with left cerebral dominance are right-
handed.

65. Cerebellum& Cerebrum
Cerebellum :-Compares intended movements
with what is actually happening to coordinate
complex, skilled movements.
Regulates posture and balance.
Cerebellum

66. CSF
•Cerebrospinal fluid (CSF) is a clear, colorless plasma-like
fluid that bathes the central nervous system (CNS).
Cerebrospinal fluid circulates through a system of cavities
found within the brain and spinal cord; ventricles,
subarachnoid space of the brain and spinal cord and the
central canal of the spinal cord.
•Most CSF is secreted by the specialized tissue called the
choroid plexus, which is located within the lateral, third and
fourth ventricles.
•The secretion of CSF equals its removal, so there is
around 150-270 milliliters of cerebrospinal fluid within the
CNS at all times.

67. Secretion
•Cerebrospinal fluid is produced by a specialized tissue
called the choroid plexus.
•Choroid plexuses are located in the walls of the lateral
ventricles and in the roofs of the third and fourth ventricles.
A choroid plexus shows numerous villi, via which it
secretes the cerebrospinal fluid. Structurally, each villus
consists of three components;
•A layer of modified ependymal cells (choroid cells), which
faces the lumen of the ventricles and secretes the CSF.
The cells show many apical villous projections and are
tightly bound to each other via tight junctions.
•A fenestrated capillary directly beneath the pia mater.

68. Compositions of CSF























69. Function of CSF
•CSF suspends to the CNS.
•Protection: CSF protects the
brain tissue from injury when
hit, by providing a fluid buffer
that acts as a shock absorber
from some forms of mechanical
injury.
•Prevention of brain ischemia:
The prevention of brain
ischemia is aided by
decreasing the amount of CSF
in the limited space inside the
skull.

70. …
•Homeostasis: CSF allows for regulation of the
distribution of substances between cells of the brain, and
neuroendocrine factors, to which slight changes can
cause problems or damage to the nervous system.
•Clearing waste: CSF allows for the removal of waste
products from the brain, and is critical in the brain's
lymphatic system.
•Metabolic waste products diffuse rapidly into CSF and
are removed into the bloodstream as CSF is absorbed.