brief anatomy of periphera nervous system

1. The Nervous System

3. Structural Classification of the
Nervous System
 Central nervous system (CNS)
Brain
Spinal cord
 Peripheral nervous system (PNS)
Nerve outside the brain and spinal cord

5. Central Nervous System (CNS)
 CNS develops from the embryonic
neural tube
The neural tube becomes the brain and
spinal cord
The opening of the neural tube becomes
the ventricles
Four chambers within the brain
Filled with cerebrospinal fluid

6. Regions of the Brain
Slide 7.27
Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings
 Cerebral
hemispheres
 Diencephalon
 Brain stem
 Cerebellum Figure 7.12

7. Functions of the Nervous System
1. Sensory input – gathering information
To monitor changes occurring inside and
outside the body (changes = stimuli)
2. Integration –
to process and interpret sensory input
and decide if action is needed.
3. Motor output
A response to integrated stimuli
The response activates muscles or glands

41. The anterior nerve root: consists of
1. Motor nerve fibres which are the axons of the nerve cells in the
anterior column of grey matter in the spinal cord and, in the
thoracic and lumbar regions,
2. Sympathetic nerve fibres which are the axons of cells in the
lateral columns of grey matter.
The posterior nerve root: consists of sensory nerve fibres.
Just outside the spinal cord there is a spinal ganglion
Sensory nerve fibres pass through these ganglia before
entering the spinal cord.
The area of skin supplied by each nerve is called dermatome

42. Anterior rami unite near their origins to form
large masses of nerves, or plexuses

44. Cervical plexus.
• Formed by the anterior rami of the first four
cervical nerves. lies opposite the 1st, 2nd, 3rd
and 4th cervical vertebrae.
• Superficial branches supply structures at
back of head and the skin of the front of the
neck to the level of the sternum.
• Deep branches supply muscles of the neck,
e.g. the sternocleidomastoid and the trapezius.

45. • The phrenic nerve:roots C3,4 and5 and
supply the muscle of the diaphragm with
impulses which stimulate contraction.

46. Brachial plexus (C5 – T1) The anterior rami of lower four
cervical nerves and a large part of the first thoracic nerve.
• Branches of the brachial plexus supply the
skin and muscles of the upper limbs and
some of the chest muscles.
• Five large nerves and a number of smaller
ones emerge from this plexus, each with a
contribution from more than one nerve root,
containing sensory, motor and autonomic
fibers

47. • Axillary (circumflex) nerve: C5, 6
• Radial nerve: C5, 6, 7, 8, Tl
• Musculocutaneous nerve: C5, 6, 7
• Median nerve: C5, 6, 7, 8, Tl
• Ulnar nerve: C7, 8, Tl
• Medial cutaneous nerve: C8, Tl.

49. The axillary (circumflex) nerve:
branches to supply the deltoid muscle, shoulder
joint and overlying skin.
Radial nerve: is the largest branch &
• supplies triceps muscle behind the humerus,
• Crosses in front of the elbow joint then winds
extensors of the wrist and finger joints.
• It continues into back of the hand to supply
the skin of the thumb, the first two fingers and
the lateral half of the third finger.

52. Musculocutaneous nerve:
• Passes downwards to lateral aspect of forearm.
• supplies the muscles of the upper arm and the
skin of the forearm.
The median nerve:
• passes down the midline of the arm in close
association with the brachial artery.
• It passes in front of the elbow joint then down
to supply the muscles

53. The ulnar nerve:
• In upper arm lies medial to the brachial artery.
• It passes behind the medial epicondyle of the
humerus to supply the muscles on the ulnar
aspect of the forearm.
• It continues downwards to supply the muscles
in the palm of the hand and the skin of the
whole of the little finger and the medial half of
the third finger.
• It gives off no branches above the elbow

54. The lumbar plexus: is formed by the anterior rami of
the first three and part of the fourth lumbar nerves.
• The plexus is situated in front of the
transverse processes of the lumbar vertebrae
and behind the psoas muscle.
• Main branches, and their nerve roots are:
• iliohypogastric nerve: L1
• ilioinguinal nerve: L1
• genitofemoral: L1, 2
• lateral cutaneous nerve of thigh: L2, 3

55. •The iliohypogastric, ilioinguinal and
genitofemoral nerve
• supply muscles and the skin in the area of the lower
abdomen,
•upper and medial aspects of the thigh and the inguinal
region.

56. • Femoral nerve: L2, 3,4
• one of the larger branches.
• cutaneous and muscular branches to supply
skin and the muscles of the front of the thigh.
• Saphenous nerve: supplies the medial aspect
of the leg, ankle and foot.
• obturator nerve: L2, 3, 4
adductor muscles of thigh and skin of the
medial aspect of the thigh

58. • lumbosacral trunk: L4, (5).
• lumbosacral trunk descends into the pelvis and
makes a contribution to the sacral plexus

60. sacral plexus: formed by the anterior rami of
lumbosacral trunk and the first, second and third sacral.
• The sacral plexus divides into a number of branches,
supplying the muscles and skin of the pelvic floor,
muscles around the hip joint.
• Sciatic nerve: largest nerve in the body. 2 cm wide at
its origin.
• It passes through the greater sciatic foramen
• Descends through the posterior aspect of the thigh
supplying the hamstring muscles.
• it divides tibial and common peroneal nerve

61. • Tibial nerve:
• descends through the popliteal fossa to the
posterior aspect of the leg where it supplies
muscles and skin.
• Passes under the medial malleolus to
supply muscles and skin of the sole of the
foot and toes.
• One of the main branches is the sural nerve
which supplies the tissues in the area of the
heel, the lateral aspect of the ankle and a part
of the dorsum of the foot

62. • Common peroneal nerve:
• descends obliquely alongthe lateral aspect of
the popliteal fossa, winds round the neck of
the fibula into the front of the leg where it
divides into
• Deep peroneal (anterior tibial)
• Superficial peroneal (musculocutaneous)
nerves.
• These nerves supply the skin and muscles of
anterior aspect of the leg and the dorsum of
the foot and toes

64. • Pudendal nerve (S2, 3, 4).
• Perineal branch supplies the external anal
sphincter, the external urethral sphincter and
adjacent skin.
• Coccygeol plexus:
• is a very small plexus formed by part of the
fourth and fifth sacral and the coccygeal nerves.
• The nerves from this plexus supply the skin in
the area of the coccyx and the levators ani and
coccygeus muscles of the pelvic floor and the
external anal sphincter

66. Thoracic nerves
• Do not intermingle to form plexuses.
• There are 12 pairs and the first 11 are the
intercostal nerves.
• They pass between the ribs supplying them, the
intercostal muscles and overlying skin.
• The 12th pair are subcostal nerves.
• The 7th to the 12th thoracic nerves also
supply muscles and the skin of posterior and
anterior abdominal walls

68. Autonomic Nervous system or involuntary
• controls the functions of the body carried out
'automatically', i.e. initiated in the brain below
the level of the cerebrum.
• Although stimulation does not occur voluntarily
the individual may be conscious of its effects,
e.g. an increase in the heart rate.

70. • The effects of autonomic control are rapid
and essential for homeostasis.
The effector organs are:
• smooth muscle
• cardiac muscle
• glands

71. Effects of autonomic stimulation include:
• Changes in rate and force of the heartbeat
• Stimulation or depression of secretion of
glands
• Vasoconstriction or vasodilatation
• Bronchoconstriction or bronchodilation
• Changes in size of the pupils of the eyes

72. Preganglionic neurone:
• cell body is in the brain or spinal cord.
• Its axon terminals synapse with the cellbody
of the postganglionic neurone in an
autonomic ganglion outside the central
nervous system
• Postganglionic neurone:
• conducts impulses to the effector organ
• Cell body is located in autonomic Ganglion.