02 Lecture ..General Anatomy-of-the-Nervous-System(General anatomy of brain and spinal cord.ppt

General anatomy of brain and spinal cord

1. ANATOMY OF THE NERVOUS
SYSTEM
Dr. Habib khan PT
DPT(KMU), MS-NMPT(RIU)

2. Structural Division OF NS
The nervous system is divided into two main parts:
Central nervous system: which consists of the
brain and spinal cord.
Peripheral nervous system: which consists of 12
pairs of cranial nerves and 31 pairs of spinal
nerves and their associated ganglia.

3. Functional Division of the NS
Functionally, the nervous system can be
divided into:
• Somatic Nervous System: Which controls
voluntary activities.
•Autonomic Nervous System: Which controls
involuntary activities.
•The nervous system, together with the
endocrine system, controls and integrates the
activities of the different parts of the body.

4. Nervous System

5. •Nervous tissue consists of two main cell
types:
•neurons (nerve cells) and
•neuroglia (non-neuronal, non-excitable glial
cells).

6. Neurons
•Neurons are the structural and functional
units of the nervous system specialized for
rapid communication.
•A neuron is composed of a cell body with
processes (extensions) called dendrites and
an axon, which carry impulses to and away
from the cell body, respectively.

8. Classification of Neuron

9. Anaxonic neurons
•no anatomical clues to
determine axons from
dendrites
• uncommon, found in brain
•functions unknown

10. Multipolar neuron
• Multiple dendrites &
single axon
• Most common type
• Most common in CNS

11. Bipolar neuron
• Two processes coming
off cell body – one
dendrite & one axon
• Only found in eye, ear &
nose

12. Unipolar (pseudounipolar)
neuron
• single process coming
off cell body, giving
rise to dendrites (at one
end) & axon (making
up rest of process)
• Common in sensory
neuron of PNS

13. Myelin sheath
•Myelin is an insulating layer that forms around
nerves, including those in the brain and spinal
cord(ependymal cells). It is made up of protein
and fatty substances.
•The purpose of the myelin sheath is to allow
impulses to transmit quickly and efficiently along
the nerve cells.
•If myelin is damaged, the impulses slow down.
This can cause diseases such as multiple sclerosis.

15. A. Multipolar motor neuron with connector neuron synapsing with it. B. Section through thoracic segment of
spinal cord with spinal roots and posterior root ganglion. C. Cross section of thoracic segment of spinal cord
showing roots, spinal nerve, and anterior and posterior rami and their branches

16. Neurotransmitters
The communication occurs by means of
neurotransmitters, chemical agents released
or secreted by one neuron, which may excite
or inhibit another neuron, continuing or
terminating the relay of impulses or the
response to them.

17. Synapse

18. Central Nervous System
•The central nervous system is composed of large numbers
of nerve cells and their processes, supported by specialized
tissue called neuroglia. Neuron is the term given to the
nerve cell and all its processes.
• The nerve cell has two types of processes, called dendrites
and an axon. Dendrites are the short processes of the cell
body; the axon is the longest process of the cell body .
•The interior of the central nervous system is organized into
gray and white matter. Gray matter consists of nerve cells
embedded in neuroglia. White matter consists of nerve
fibers (axons) embedded in neuroglia.

19. Gray and white Matter of the brain

20. Peripheral Nervous System
The peripheral nervous system consists of the
cranial and spinal nerves and their associated
ganglia.

21. Peripheral nervous system

22. Cranial Nerves
•There are 12 pairs of cranial nerves that leave
the brain and pass through foramina in the
skull.
•All the nerves are distributed in the head and
neck except the Xth (vagus), which also
supplies structures in the thorax and abdomen

23. Cranial Nerves

24. Spinal Nerves
 A total of 31 pairs of spinal nerves leave the
spinal cord and pass through intervertebral
foramina in the vertebral column.
 The spinal nerves are named according to the
region of the vertebral column with which they
are associated: 8 cervical, 12 thoracic, 5 lumbar,
5 sacral, and 1 coccygeal.
 Note that there are eight cervical nerves and
only seven cervical vertebrae and that there is
one coccygeal nerve and four coccygeal
vertebrae.

26. •Each spinal nerve is connected to the spinal cord
by two roots: the anterior root and the posterior
root . The anterior root consists of bundles of
nerve fibers carrying nerve impulses away from
the central nervous system . Such nerve fibers
are called efferent fibers.
•Those efferent fibers that go to skeletal muscle
and cause them to contract are called motor
fibers. Their cells of origin lie in the anterior gray
horn of the spinal cord.

27. •The posterior root consists of bundles of nerve
fibers that carry impulses to the central nervous
system and are called afferent fibers . Because
these fibers are concerned with conveying
information about sensations of touch, pain,
temperature, and vibrations, they are called
sensory fibers.
•The cell bodies of these nerve fibers are situated
in a swelling on the posterior root called the
posterior root ganglion.

29. •At each intervertebral foramen, the anterior and posterior
roots unite to form a spinal nerve . Here, the motor and
sensory fibers become mixed together, so that a spinal
nerve is made up of a mixture of motor and sensory fibers .
• On emerging from the foramen, the spinal nerve divides
into a large anterior ramus and a smaller posterior ramus.
The posterior ramus passes posteriorly around the
vertebral column to supply the muscles and skin of the
back .
• The anterior ramus continues anteriorly to supply the
muscles and skin over the anterolateral body wall and all
the muscles and skin of the limbs.

31. •In addition to the anterior and posterior rami,
spinal nerves give a small meningeal branch
that supplies the vertebrae and the coverings
of the spinal cord (the meninges).
• Thoracic spinal nerves also have branches,
called rami communicantes, that are
associated with the sympathetic part of the
autonomic nervous system.

33. •At the root of the limbs, the anterior rami join
one another to form complicated nerve
plexuses .
•The cervical and brachial plexuses are found
at the root of the upper limbs, and the lumbar
and sacral plexuses are found at the root of
the lower limbs.

34. Nerve Plexus

35. •The nerve plexus is actually made up of a
multitude of nerve branches. These branches
come from the spinal nerves, except for the
thoracic spinal nerves 2 through 12. The
remaining nerves donate their anterior rami,
which branch off from the spinal nerves only
to adjoin with each other.

37. Autonomic Nervous System
Responsible for control of involuntary or visceral
bodily functions visceral functions
•cardiovascular
•Respiratory
•digestive
•urinary
•reproductive functions
•Key role in the bodies response to stress

38. Autonomic Nervous System
Sympathetic nervous system
(Thoracolumber outflow)
allow body to function under stress
fight or flight
Parasympathetic nervous system
(Craniosacral outflow)
controls vegetative functions
feed or breed or rest and repose
constant opposition to sympathetic system

39. Autonomic nervous system