Peripheral Nervous System

The peripheral nervous system

the nervous system outside the brain and spinal cord

PNS relation with CNS

nerves allow the CNS to receive information and initiate action

Attach to the brain

cranial nerves

numbered from I to XII

cranial nerves

Where do cranial nerves I and II attach to

the forebrain

Where do all other cranial nerves attach

the brain stem

cranial nerves primarily serve what 2 structures

head and neck structures

Vagus nerve X

the only cranial nerve that extends into the abdomen

The Olfactory nerve function

• sensory

• Olfaction (smell)

Anosmia

the lost of smell (partial or permanent)

The sensory nerves of smell

olfactory nerves cranial I

CN II: the optic nerve function

• sensory 

• vision

Anopsia in optic nerves

vision loss or defect in the vision field

the sensory nerve of vision

Optic nerves cranial II

CN III: the oculomotor nerve function

motor function

How many extra ocular eye muscles does the oculomotor nerve control

4 of the 6

oculomotor nerve responsibility

moving the eye superiorly, inferiorly, medially

What is happening in the picture?

• external strabismus

the two extraocular eye muscles not served by CN III are unopposed and move the eye laterally + inferiorly. The patient experiences double vision

innervates 4 of the 6 extrinsic eye muscles

Oculomotor nerves cranial III

the superior oblique muscle

moves eye inferolaterally (below and to one side)

what is happening in this picture?

• trochlear nerve palsy

inferior oblique muscle is unopposed and moves the eye superomedially (up and towards the middle). The patient experiences double vision

innervates the superior oblique muscle (an extrinsic eye muscle)

trochlear nerves of the IV cranial nerve

CN V: the trigeminal nerve function

mixed (sensory and motor) function in 3 branches

Ophthalmic (v1)

sensory from the forehead, eyelids, and nose

Maxillary (V2)

sensory from lower eyelid, upper lip, and cheek

Mandibular (V3)

sensory to the lower jaw; motor to the muscles of mastication

CN V: the trigeminal nerve example

dental anesthesia

CN VI: the abducens nerve function

motor funcition

How many extra-ocular eye muscles does the abducens nerve control?

1 of the 6

Lateral rectus muscle in the abducens nerve function

moves eye laterally

What is happening in this picture?

• internal strabismus 

medial rectus muscle is unopposed and moves the eye medially. The patient experiences double vision.

Abducts the eyeball—innervates the lateral rectus muscle

VI (#6) abducen nerves

CN VII: the facial nerve function

mixed (sensory and motor) function

Sensory in the VII facial nerve

gustation (taste) from anterior 2/3 of tongue

Motor in the VII facial nerve

controls muscles of the face (facial expression)

innervates muscles of facial expression+taste on anterior (2/3 of the tongue)

CN VII facial nerves

What is happening in this picture?

CN VII: the facial nerve: bell’s palsy

CN VIII: the vestibulocochlear nerve function

sensory function

two types of sensory function in CN VIII: the vestibulocochlear nerve

Audition (hearing)

equilibrium (balance)

Example of CN VIII: the vestibulocochlear nerve

nerve deafness and vertigo

if the cochlear branch is damaged=

nerve deafness can occur

if the vestibular branch is damaged=

vertigo (dizziness, loss of balance, nausea, rapid eye movement) can occur

Sensory nerve of hearing and balance

CN VIII: the vestibulocochlear nerve

CN IX: the glossopharyngeal nerve function

mixed (sensory and motor) function

Sensory function in CN IX: the glossopharyngeal nerve

gustation (taste) from posterior 1/3 of tongue

Motor function in CN IX: the glossopharyngeal nerve

pharyngeal muscles (swallowing)

motor control of pharynx elevation (swallow reflex) + taste on posterior 1/3 of tongue

CN IX: the glossopharyngeal nerve

What is happening in this picture?

impaired swallowing (IX: the glossopharyngeal nerve)

another example of the glossopharyngeal nerve

loss of taste (ageusia) in posterior tongue

CN X: the Vagus nerve sensory function

sensation from organs (visceral sensory)

CN X: the Vagus nerve motor function

primary parasympathetic (“rest and digest”) nerve to the internal organs (visceral motor division)

Example of CN X: the Vagus nerve

• death

complete damage of the vagus nerve is incompatible with life

Slight damage symptoms of the Vagus nerve sensory function

impairments to digestion or leading to hoarseness + loss of voice

A mixed sensory and motor nerve

X Vagus Nerves

“Wanders” into thorax and abdomen

X Vagus nerves

Parasympathetic innervation of organs

X Vagus nerves

CN XI: the accessory nerve function

motor function

What 2 muscles does the XI: the accessory nerve control

• sternocleidomastoid muscle

• trapezius muscle

what is happening in this picture?

• damage of XI: the accessory nerve

accessory nerve damage

CN XII: the hypoglossal nerve function

motor function

• controls tongue movement

What is happening in this picture?

• Tongue deviation of the hypoglossal nerve

unilateral nerve damage leads to tongue deviation

bilateral damage of the tongue leads to what?

tongue paralysis

Runs inferior to the tongue

XII hypoglossal nerve

innervates the tongue muscles

XII hypoglossal nerve

how many pairs of spinal nerves and what do they contain?

31 pairs; contain thousands of nerve fibers

Connect to the spinal cord

spinal nerves

named for point of issue from the spinal cord

spinal nerves

C1-C8

8 pairs of cervical nerves

T1-T12

12 pairs of thoracic nerves

L1-L5

5 pairs of lumbar nerves

S1-S5

5 pairs of sacral nerves

CO1

1 pair of coccygeal nerves