bio 161 _lab__9_cranial_nerves

SCOTT.LEHBAUER@LETHBRIDGECOLLEGE.AB.CA

Cranial Nerves

Cranial Nerves

Cranial nerves are nerves that originate in the cranium

There are 12 pairs of cranial nervesThe first two pairs attach to the forebrain The others originate in the brain stem

Cranial Nerves

I – Olfactory Nerve

FUNCTIONPurely sensory

nerveCarries afferent

impulses for the sense of smell

TEST smell bilaterally

Olfactory Nerve (83)

II – Optic Nerve

FUNCTIONPurely sensoryCarry afferent

impulses for vision

TEST See bilaterally Optic Nerve (84)

III – Oculomotor Nerve

FUNCTIONChiefly motor nerveCause pupil

constrictionEye movement

TEST Pupil contraction

when light is shined into eye Oculomotor Nerve (85)

IV – Trochlear Nerve

FUNCTIONPrimarily motor

nervesCause eye

movement in one of the extrinsic eye muscles (Superior oblique)

TESTTracking of eye from

left to right

Trochlear Nerve (86)

V – Trigeminal Nerve (The largest Cranial Nerve)

FUNCTION Mixed nerve Provides sensory

and motor input for the face and associated structures

TEST Sensation on three

sections of the face bilaterally

Trigeminal Nerve (87)

VI – Abducens Nerve

FUNCTIONMotor nerveSupplies motor

fibers to the lateral rectus muscles which move the eye

TEST eye tracking from

left to right Abducens (88)

VII – Facial Nerve

FUNCTIONMixed nerve the chief motor

nerve for the muscles of the face

TEST Wrinkle foreheadClose eyesmile Facial Nerve (89)

Bell’s Palsy

Is characterized by paralysis of the face muscles on the affected side and partial loss of taste sensation.

The lower eyelid droops, corner of the mouth sags, tears may continuously drip from eye to eye

These symptoms are caused by damage to the facial nerve

VIII – Auditory Nerve

FUNCTIONMostly sensory,

some motorBranches transmit

the afferent fibers affecting the sense of equilibrium and hearing

TEST Bilateral hearingBalance with your

eyes closedAuditory Nerve (90)

IX – Glossopharyngeal Nerve

FUNCTIONMixed nerveProvides motor

fibers to the muscles of the tongue and pharynx

TEST Gag reflex Glossopharyngeal Nerve (91)

X – Vagus Nerve

FUNCTION Mixed nerve Motor fibers supply

heart, lungs and abdominal viscera

Regulates heart rate, breathing rate and digestive system activity

TEST Say “Ah” uvula is

midline Swallow

Vagus Nerve (92)

XI – Spinal Accessory Nerve

FUNCTIONMotor Nerveinnervates

trapezius and Sternocleidomastoid

TEST Shoulder Shrug

against resistance Spinal Accessory Nerve (93)

XII – Hypoglossal Nerve

FUNCTIONMotor Nerve

(primarily motor)Carries motor

fibers to the tongue

TESTStick out tongue

and look for tremors Hypoglossal Nerve (94)