Chapter 6

Cranial and Spinal Nerves

I. Cranial Nerves: 12 pairs, part of the PNS

A. I. = Olfactory:

1. Sensory: olfaction (smell)

B. II. = Optic:

1. Sensory: vision

C. III. = Oculomotor:

1. Motor - Voluntary: to superior, medial, inferior rectus, & inferior oblique

2. Motor - Involuntary:

a. Circular Muscle of Iris (constricts pupil)

b. Ciliary Muscle for changing the shape of the Lens

3. Sensory - Proprioception (detection of skeletal muscle and joint position)

D. IV. = Trochlear:

1. Motor - Voluntary to superior oblique

2. Sensory - Proprioception

E. V. = Trigeminal:

1. Sensory:

a. Cutaneous receptors of face (also; surface of eye, surface of tongue, lining of mouth, lining of nose, teeth & external ear)

b. Proprioception

2. Motor - Voluntary to muscles of mastication

F. VI. = Abducens:

1. Motor - Voluntary to lateral rectus

2. Sensory - Proprioception

G. VII. = Facial:

1. Sensory:

a. Taste, from the taste buds on the anterior 2/3rds of the tongue;

b. Proprioception

2. Motor:

a. Voluntary: to muscles of facial expression

b. Involuntary: to Lacrimal (tear), Submandibular (salivary), & Sublingual (salivary) glands

H. VIII. = Vestibulocochlear:

1. Sensory: hearing & equilibrium

I. IX. = Glossopharyngeal:

1. Sensory:

a. Taste, from the taste buds on the posterior 1/3rd of the tongue

b. Proprioception

2. Motor:

a. Voluntary: to pharynx (swallowing)

b. Involuntary: to Parotid (salivary) gland

J. X. = Vagus:

1. Sensory:

a. from smooth muscle in the organs of the thorax & abdomen

b. Proprioception

2. Motor:

a. Voluntary: to Pharynx (swallowing) & Larynx (phonation)

b. Involuntary: regulates contraction of smooth muscle and gland secretion of the organs in the thorax and abdomen

K. XI. = Accessory:

1. Cranial portion:

a. Motor - Voluntary to Pharynx (swallowing) and Larynx (phonation)

b. Sensory - Proprioception

2. Spinal portion:

a. Motor - Voluntary to Trapezius & Sternocleidomastoid

b. Sensory - Proprioception

L. XII. = Hypoglossal:

1. Motor - Voluntary to tongue muscles (swallowing and speech)

2. Sensory - Proprioception

Which of the following would be damaged if you couldn't move your eye straight up?

a. IV, trochlear

b. III, oculomotor

c. V, trigeminal

d. VII, facial

e. VI, abducens

I. Spinal Nerves: part of the PNS, 31 pairs, all mixed (both sensory & motor)

A. Structure

1. Dorsal root (sensory)

2. Ventral root (motor) When these two come together = Spinal Nerve (about 1 inch long!)

3. Dorsal root ganglion - contains cell bodies of sensory neurons

4. Spinal nerve - divides into Dorsal Ramus (goes posteriorly, short) & Ventral Ramus (goes laterally & anteriorly, & extends out into extremities, long)

B. Nerve plexus - networks formed by ventral rami only

1. Cervical plexus

a. Phrenic n. - to diaphragm

2. Brachial plexus

a. Axillary n. - shoulder

b. Radial n. - posterior arm, extensors

c. Musculocutaneous - anterior upper arm, flexors

d. Ulnar n. - medial, anterior forearm, & medial hand (4th & 5th fingers)

e. Median n. - lateral, anterior forearm, & lateral hand (1st, 2nd, & 3rd fingers)

3. Lumbar plexus

a. Femoral n.: Motor - to anterior thigh (Quadriceps)

Sensory - from anterior and lateral thigh and medial leg & top of foot

b. Obturator n. - to medial thigh (Adductors)

4. Sacral plexus

a. Many small nerves to lower back, posterior pelvis, & perineum

b. Sciatic n. - the Sciatic N. provides innervation to the posterior thigh muscles (hamstrings). Just above the knee the Sciatic N. divides into the;

i. Tibial Nerve - posterior leg (plantar flexors) and sole

ii. Common Fibular (Peroneal) Nerve - to anterior and lateral muscles of leg and foot.

Which of the following would be damaged if you were unable to extend your leg?

a. sciatic

b. femoral

c. obturator

d. tibial

e. common fibular (peroneal)


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