Lecture prepared by Dr. Hamid Husain , Riphah international university

3. INTRODUCTION TO
NERVOUS SYSTEM-02
HAMID HUSSAIN

4. DIVISIONS OF
THE NERVOUS
SYSTEM
Peripheral nervous system: which consists of 12
pairs of cranial nerves and 31 pairs of spinal
nerves and their associated ganglia.
Central nervous system: which consists of the
brain and spinal cord.
The nervous system is divided into two main
parts:

5. FUNCTIONAL DIVISION OF THE NERVOUS SYSTEM
Functionally, the nervous system can be further 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.

6. NERVOUS SYSTEM

7. 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.

8. 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

9. PERIPHERAL NERVOUS SYSTEM
The peripheral nervous system consists of the cranial and spinal nerves and their
associated ganglia.

10. PERIPHERAL NERVOUS SYSTEM

11. 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

12. CRANIAL NERVES

13. 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.

15. • 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.

16. • 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.

18. • 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.

20. • 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.

21. GRAY AND WHITE MATTER OF THE BRAIN

23. • 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.

24. NERVE PLEXUS

25. • 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.

27. 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

28. AUTONOMIC
NERVOUS
SYSTEM
Sympathetic nervous system
allow body to function under stress
fight or flight
Parasympathetic nervous system
controls vegetative functions
feed or breed or rest and repose
constant opposition to sympathetic system

29. AUTONOMIC NERVOUS SYSTEM

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

31. 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.

34. 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.

35. SYNAPSE

36. MYELIN SHEATH
• Myelin is an insulating layer that forms around nerves, including those in the
brain and spinal cord. 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.

38. CLASSIFICATION
OF NEURON

39. ANAXONIC NEURONS
• no anatomical clues to
determine axons from dendrites
• functions unknown

40. Multipolar neuron
• multiple dendrites & single
axon
• most common type

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

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

43. THANKS

44. KARORA (SHANGLA)