ANATOMY

1. PERI[HERAL NERVOUS
SYSTEM

2. Peripheral nervous system (PNS)
 It is part of nervous system outside the CNS
 Consist mainly of the nerves that extends from the brain & spinal cord
 Spinal nerves: carry impulse to & from the spinal cord
 Cranial nerves: carry impulse to & from the brain
NB: PNS serves as a communication line linking all parts of the body
to CNS

3. Subdivision of PNS
• Afferent or sensory division
 Afferent means “carrying toward”
 Consist of all incoming sensory pathways
 That means it consist of nerve fibers that convey impulses to the CNS
from the sensory receptors located throughout the body e.g. skin.

4. Subdivision of PNS (cont.)
• Efferent or motor division:
 Efferent means “carrying away” or “bring about motor response
 Consist of all incoming sensory pathways
 That means they transmit impulse from CNS to the effector organs
e.g. the muscle & the glands
 These impulse activate muscle to contract & glands to secrete

5. Motor division has two main parts
• Somatic & autonomic nervous system
NB: that means the motor division is involved in activities that are
voluntary and involuntary

6. Motor division
1. Somatic nervous system
 It is often referred to as the voluntary nervous system since it allows
us to consciously control our skeletal muscle
 It is composed of somatic nerve fibers that conduct impulses from the
CNS to skeletal muscles

7. Motor division (cont.)
Autonomic nervous system
 Autonomic means “a law unto itself” we can not control activities
such as pumping of heart, or movement of food through GIT
 It is also referred to as involuntary NS
 Consist of visceral motor nerve fibers that regulate the activity of
smooth muscles, cardiac muscle & glands

8. The Autonomic NS has 2 functional
subdivision
• The sympathetic &
• Parasympathetic division
NB: they bring about opposite effects on the activity of the same
visceral organs. What one subdivision stimulate, the other inhibits

9. Autonomic subdivision
• Sympathetic division
 Prepares the body to deal with immediate threats to the external
environment
 Produces “fight-or-flight” response
Parasympathetic division
 Coordinates the body’s normal resting activity
 Sometimes called “rest & repair” division

10. The reflex arc
• Reflex is a rapid, predictable motor response to a stimulus
• Reflex prevent us from having to think about all the little details of
staying upright, and alive, helping us maintain posture, avoid pain and
control visceral activities

11. Reflex arc
• Is a single conduction route to & from the CNS, with the electrical
signal beginning in the receptors & ending in the effectors
• Three neuron arc: most common & consist of Afferent, interneurons
& efferent neurons
a) Afferent neurons: conduct impulses to the CNS from receptor
b) Efferent neurons: conduct impulse from CNS to effectors (muscle or
glandular tissue)

12. Components of reflex arc
• Receptor: site of the stimuli
• Sensory neuron: transmits afferent impulse to CNS
• Integration center: within the CNS
• Motor neuron: conducts efferent impulses from the integration
center to an effector organs.
• Effector: muscle fiber or glands cell that responds to the efferent
impulse by contracting or secreting

13. Reflex arc (cont.)
• Reflex are classified functionally as somatic reflex if they activate
skeletal muscle, or
• As autonomic (visceral) reflex if they activate smooth or cardiac
muscle or glands

14. PERIPHERAL NEARVOUS SYSTEM (PNS)
• The PNS is made up of the 31 pairs of spinal cord, & 12 pairs of cranial
nerves that emerge from the brain

15. SPINAL NERVES
• There are 31 pairs of spinal nerves
• They are named and grouped according to the vertebrae with which
they are associated
• They do not have special names like cranial nerves
• Each pair of nerves contain thousands of nerve fibers
• They supply all parts of the body except the brain

16. Spinal nerves (cont)
• All spinal nerves are mixed nerves
• There are
 8 cervical nerve pairs (C1 through C8)
 12 thoracic nerve pairs (T1 through T12)
 5 lumber nerve pairs (L1 through L5)
 5 sacral nerve pairs (S1 through S5)
 1 coccygeal nerve pair (Co 1)

18. Structure of the spinal nerve
• Each spinal nerve attaches to spinal cord by a Ventral (anterior) root
and dorsal (posterior) root
• The dorsal root of each spinal nerve is easily recognised by swelling
called the dorsal root ganglion
• All spinal nerves are mixed nerve

19. Rami of Spinal Nerves

20. Nerve plexuses
• Plexuses: is the complex network formed by ventral rami of most
spinal nerve except (T2 trough T12)
• They join together to make one nerve
• They are regrouped before proceeding to supply skin, bones, muscles
& joints of particular area
• These structures have nerve supply from more than one spinal nerve,
therefore damage to one spinal nerve does not cause loss of
functions of a region

21. Plexuses (cont)
• In the thoracic region the anterior rami does not form plexus
• There a 5 plexuses on each side of the vertebral:
 Cervical
 Brachial
 lumber
 Sacral
 Coccygeal (small plexus)

22. Cervical plexus
• Located deep within the neck
• Formed by the anterior rami of the first four cervical nerves
• Lie under the protection of stenocledomastoid muscle
• Superficial branch supply the structures of the back, & side of the
head & the skin of the front of the neck to the level of sternum

23. Cervical (cont)
• Deep branches supply the muscles of the neck e.g.
Stenocledomastoid & the trapezium
• The phrenic nerve found in this plexus supply the diaphragm with
impulses that stimulate the contraction, initiating inspiration
NB: irritation to this nerve cause spasms of the diaphragm or hiccup. If
both phrenic nerve is damaged, respiratory arrest will occur

24. Brachial plexus
• Found deep within the shoulder
• Pass through C5 though T1
• Branches supply the skin & muscle of the upper limbs & some of the
chest muscle
• The axillary (circumflex) nerve found around humerus supply deltoid
muscles, shoulder joint

25. Brachial (cont)
• Radial nerve: is the largest branch of brachial plexus. Supply the
triceps muscle behind humerus, wrist & finger joints. It also supply
the skin of the thumb, the first finger & lateral half of the third finger
• Musculocutaneous nerve: passes downwards to the lateral aspect of
the forearm to supply the muscles of the upper arm & skin of the
forearm

26. Brachial (cont)
• The medial nerve: passes down the midline of the arm in close
association with brachial artery. Pass in front of the elbow joint.
supply the muscle of the front forearm. Continue to the hand to
supply the small muscle of the skin of the front thumb
activates muscle of the forearm, flex the fingers

27. Brachial plexus
• Ulna nerve: largest branch of brachial plexus.
supply the muscles of the ulna aspect of the forearm, the palm of the
hand & the skin of the whole of little finger & the medial half of the
third finger

28. Lumber plexus
• Located in the lumber region of the back of the psoas muscle
• Formed by fibers of the first four lumber nerve (L1 through L4)
• Femoral nerve is one of the several nerve that emerge from the
lumber plexus
• It divides into many branches to supply the thigh & the leg

29. Sacral plexus
• Located in the pelvic cavity in the anterior surface of the periformis
muscle
• Formed by intermingling fibers from L4 though S4
• Because of their close proximity & overlap of fibers lumber & sacral
plexuses are considered together as the lumbasacral plexus
• Supply muscle of the skin of pelvic floor & muscle around the hip joint
& pelvic organs.

30. CRANIAL NERVES
• Twelve pairs of cranial nerves connect to the brain mostly brain-stem
• Both names & numbers identify the cranial nerves
• Their name suggest either their distribution or their functions
• Their numbers indicate the order in which they connect to the brain
from anterior or posterior

31. Cranial nerves (cont.)
• Cranial nerves are made up of bundle of axons
 Mixed cranial nerve: contains axons of sensory & motor neurons
 Sensory cranial nerve: contain axons of sensory neurons only
 Motor cranial nerve: consist mainly of motor axons, also contain
small number of sensory fibers.

32. Cranial nerves (cont.)
1. Olfactory nerve
Composed of axons of neurons whose dendrites & cell bodies lie in
nasal mucosa & terminate in the olfactory bulb
Caries information about sense of smell

33. Cranial nerve (cont.)
Optic nerve
Composed of axons from the innermost layer of sensory neurons of
the retina
Carries visual information from the eye to the Brain

34. Oculomotor nerve
Fibers of each oculomotor nerve originate from cells in the
oculomotor nucleus & extend to some of the external eye movement
Efferent autonomic fiber are also present, which extent to the
intrinsic muscle of the eye to regulate amount of light to the eye &
aid in focusing on near object
Sensory fibers from proprioceptors in the eye muscle are present also

35. Trochlear nerve
Motor fibers originate in the cells of the midbrain & extend to the
superior oblique of the eye
Also contains afferent fibers from proprioceptors in the superior
oblique muscle of the eye

36. Trigeminal nerve
Has 3 branches, ophthalmic nerve, maxillary nerve & mandibular
nerve
Sensory neurons carry afferent impulses from skin & mucosa of head
& teeth to cell bodies in trigeminal ganglion
Motor fiber originate in trifacial motor nucleus & extent to the
muscle of mastication though the mandibular nerve

37. Adducens nerve
Motor nerve with fibers originating from a nucleus in the pons on the
floor of the fourth ventricle extending to lateral rectus muscle of the
eye
Contain afferent fiber from proprioceptors in the lateral rectus
muscle

38. Facial nerve
Motor fibers originate from a nucleus in lower part of pons extended
to superficial muscles of the face & scalp
Autonomic fibers extend to submaxillary & sublingual salivary glands
Also contains sensory fiber from test buds

39. Vestibulocochler nerve
Two distal divisions that are both sensory: vestibular nerve &
cochlear nerve
Vestibular nerve fiber originate in the semicircular canals in inner ear
& transmit impulses that result in sensations of equilibrium
Cochlear nerve fiber originate in the organ of corti in the cochlear of
the inner ear & transmit impulses that result in sensation of hearing

40. Glossopharyngeal nerve
Composed sensory, motor & autonomic nerve fibers
Supplies fibers to tongue, pharynx & carotid sinus

41. Vagus nerve
Composed of sensory & motor fibers with many widely distributed
branches
Sensory fibers supply pharynx, larynx, trachea, heart, lungs, bronchi,
esophagus, stomach, small intestines & gall bladder
Somatic motor fibers innervate the pharynx & larynx & are mostly
autonomic fibers

42. Accessory nerve
Motor nerve that is an “accessory” to the vagus nerve
Innervates thoracic & abdominal viscera, pharynx, larynx, trapezium
& sternocleidomastoid

43. Hypoglossal nerve
Composed of motor & sensory fibers
Motor fibers innervate the muscle of the tongue
Contains sensory fibers from proprioceptors in muscle of the tongue

44. Somatic nervous system
• Is the part of peripheral nervous system
• Associated with voluntary movement, control body movement via
skeletal muscles
• Consist of efferent nerves responsible for stimulating muscle
contraction
• Made up of nerves that connect to skin, sensory organs & all skeletal
muscle

45. Functions of SNS
• Responsible for carrying motor & sensory information both to & from
the CNS
• This system is responsible for all voluntary muscle movement
• SNS control such voluntary actions such as walking, smiling through
the use of efferent motor nerves