Exam 3 - Cranial Nerves***MOST IMPORTANT*** Flashcards
Each cranial nerve has a number indicating the order, from ____ to____, in which it arises from the brain
anterior to posterior
Each has a name that designates the nerve’s ___
function
Cranial nerves are functionally either sensory (afferent) neurons only, or mixed (some combination of afferent (sensory) and efferent (motor) neurons)
TRUE
Those that are mixed may be primarily ___ or primarily ____
primarily motor OR primarily sensory
Two cranial nerves contain only sensory neurons:
Cranial nerve I (olfactory)
Cranial nerve II (optic)
One cranial nerve is so predominantly sensory that its motor function is frequently overlooked:
Cranial nerve VIII (vestibulocochlear)
Cranial nerves I, II, and VIII are thus called…
sensory nerves (even though CN VIII is not exclusively sensory)
Motor Cranial Nerves
There are no cranial nerves that are exclusively motor throughout their entire length, however ______ are commonly called motor nerves because their function is predominantly motor
cranial nerves III, IV, VI, XI, and XII
They are often said to be “mixed, mainly motor” or “mixed, primarily motor” (as in the following slides)
Motor Cranial Nerves
It is a general principle that the sensory function of such nerves is ______ of the muscles over which they exert motor control (the following slides assume that fact, and do not necessarily repeat proprioceptive functions)
proprioception
Mixed cranial nerves
Cranial nerves ________ are termed mixed nerves because they have substantial motor and sensory functions, and contain axons of both sensory and motor neurons
Cranial nerves V, VII, IX, and X
Single function motor cranial nerves
Most cranial nerves that have a motor function innervate more than one muscle, but the sole mission of two cranial nerves is to innervate a single muscle each:
Trochlear (IV) innervates the superior oblique
Abducens (VI) innervates the lateral rectus
Trochlear (IV) innervates the superior oblique
Abducens (VI) innervates the lateral rectus
Both muscles are extrinsic muscles of the eye
Each nerve is primarily motor, with proprioception of its muscle being its sensory function
No motor function nerves?
Cranial Nerve I and II
Olfactory and Optic
Remember this cranial nerve is predominantly sensory, but DOES have a motor function
CN VIII
vestibulocochlear
Somatic and autonomic
All motor cranial nerves have neurons that innervate ____ (skeletal) muscles
somatic
Some motor cranial nerves also have autonomic motor axons:
III (oculomotor)
VII (facial)
IX (glossopharyngeal)
X (vagus)
The autonomic axons are part of the parasympathetic division, and innervate….
glands, smooth muscle, and cardiac muscle
Entirely sensory
Contains axons that conduct nerve impulses for the sense of smell (olfaction)
Olfactory bulb and olfactory tract are not CN I
Short function: smell
I – Olfactory
Olfactory bulb and olfactory tract are NOT…
CN I
CN I is sensory or motor?
sensory ENTIRELY
Olfactory receptors are bipolar neurons:
CN I (olfactory)
Bundles of axons of the receptors extend through the ____of the ____
Those bundles taken together are the ____
cribriform plate of the ethmoid
olfactory nerve
Olfaction is assessed by having patient state whether or not they can perceive a common….
non-offensive smell such as soap, cloves, flavored Chapstick®, coffee, or vanilla
Loss of the sense of smell is called…
anosmia
Entirely sensory
Contains myelinated axons that conduct nerve impulses for vision
Optic nerve versus optic tract; optic chiasma
Short function: vision
CN II - Optic
Assessment of peripheral vision is one test associated with
cranial nerve II
Mainly motor
Controls extrinsic eye muscles not innervated by IV and VI
Innervates intrinsic eye muscles: ciliary muscle (on lens) sphincter pupillae (iris)
Short function: eye movement
III – Oculomotor
Innervates intrinsic eye muscles: ciliary muscle (on lens) sphincter pupillae (iris)
III – Oculomotor
III – Oculomotor Innervates intrinsic eye muscles:
ciliary muscle (on lens) sphincter pupillae (iris)
Innervates most extrinsic eye muscles
Parasympathetic innervation to intrinsic eye muscles
Innervates levator palpebrae superioris (muscle of the upper eyelid)
III – Oculomotor
Innervates most extrinsic eye muscles
III – Oculomotor
III – Oculomotor Innervates…
Innervates levator palpebrae superioris (muscle of the upper eyelid)
This is the pupillary light response test
Both pupils should constrict when light is shined in only one eye
III – Oculomotor
Mainly motor
Smallest of the cranial nerves
Innervates superior oblique muscle of the eye
Only cranial nerve to arise from the posterior aspect of the brain stem
Short function: eye movement
IV – Trochlear
Smallest of the cranial nerves
IV – Trochlear
Innervates superior oblique muscle of the eye
IV – Trochlear
Only cranial nerve to arise from the posterior aspect of the brain stem
IV – Trochlear
Short function: eye movement
IV – Trochlear
IV – Trochlear
The trochlea (trochle = pulley) is a pulleylike loop through which the tendon of the _____ muscle passes
The superior oblique moves the eyeball…
The trochlea (trochle = pulley) is a pulleylike loop through which the tendon of the superior oblique muscle passes
The superior oblique moves the eyeball inferiorly and laterally
The superior oblique moves the eyeball
inferiorly and laterally
The trochlea (trochle = pulley) is a pulleylike loop through which the tendon of the _____ muscle passes
superior oblique
Following a moving object with the eyes assesses cranial nerves III, IV, and VI since all three innervate extrinsic muscles of the eye
IV – Trochlear
Mixed
Largest of the cranial nerves
Emerges from pons isolated from other cranial nerves
Provides sensory neurons to face, head, and anterior 2/3 tongue
Motor neurons control chewing movements
Short function: mastication, facial sensation
V – Trigeminal