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A&P Test 3 Cranial Nerves (4)

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T/F Cranial nerves are all sensory (afferent)
False
Can be both sensory and motor
Which cranial nerves are ONLY sensory?
Cranial nerve I (olfactory)
Cranial nerve II (optic)
Is CN VIII sensory or motor?
Both
Predominantly sensory
- Cranial nerves I, II, and VIII are thus called sensory nerves (even though CN VIII is not exclusively sensory)
Which CNs are called motor nerves?
CN 3, 4, 6, 11, and 12
T/F Cranial nerves III, IV, VI, XI, and XII are motor their entire length
False
- NO cranial nerves are exclusively motor their entire length
- CN 3, 4, 6, 11, and 12 are commonly called motor nerves because their function is predominantly motor but they are mixed
What is the sensory function for Cranial nerves III, IV, VI, XI, and XII?
Proprioception of the muscles over which they exert motor control
Describe the sensory pathway for Cranial nerves 3, 4 and 6
Associated with eye movement
- Their proprioceptive sensory axons begin toward brain in the corresponding nerve
- Soon leave nerve to join the ophthalmic branch of the trigeminal nerve
Describe the sensory pathway for CN 11 and 12
Sensory axons that originate from proprioceptors in muscles supplied by these nerves begin their course toward the brain within the corresponding nerve
- Later leave nerve
- Accessory (XI) nerve sensory axons join nerves of the cervical plexus
- Hypoglossal (XII) sensory axons join cervical spinal nerves
Which CNs are termed mixed nerves?
CN 5, 7, 9, 10

Substantial motor and sensory functions, and contain axons of both sensory and motor neurons
Which 2x cranial nerves innervate only a single muscle?
4 and 6
Trochlear (4) innervates superior oblique
Abducens (6) innervates lateral rectus

- Both muscles are extrinsic muscles of the eye
- Each nerve is primarily motor, with proprioception of its muscle being its sensory function
T/F All motor cranial nerves have neurons that innervate somatic (skeletal) muscles
True
Which CNs have autonomic motor axons?
3, 7, 9, 10

- 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
CN I - Olfactory
- 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
Olfactory receptors are ____ neurons
Bipolar
Bundles of axons of the receptors extend through the ___ ____ of the ethmoid
Cribriform plate

Those bundles taken together are the olfactory nerve
The olfactory nerves transit the olfactory foramina in the cribriform plate of the ethmoid bone
Loss of the sense of smell is called what?
Anosmia

Olfaction - assessed if they can/cannot perceive a common non-offensive smell such as soap, cloves, flavored Chapstick, coffee, or vanilla
Which CN is entirely sensory and contains axons that conduct nerve impulses for vision?
CN 2 - Optic

Optic nerve versus optic tract; optic chiasma
What are the light sensitive cells in the retina?
Rods and cones

- They relay signals to bipolar cells, which convey the impulses to ganglion cells
- Axons of the ganglion cells form the optic nerve
Assessment of peripheral vision is one test associated which cranial nerve?
CN 2

- The optic nerve passes through the optic foramen between the superior and inferior portions of the lesser wing of the sphenoid bone
Which CN is mainly motor that 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
CN 3 innervates the muscle of the upper eyelid called what?
Levator palpebrae superioris

- Innervates most extrinsic eye muscles
- Parasympathetic innervation to intrinsic eye muscles
How do you test the Oculomotor (CN3)?
Pupillary light response test

- Both pupils should constrict when light is shined in only one eye
- The oculomotor, trochlear, ophthalmic, and abducens nerves transit the superior orbital fissure
What is the smallest of the CNs and inervates the superior oblique muscle of the eye?
CN 4 - Trochlear
T/F CN 3 is the only cranial nerve to arise from the posterior aspect of the brain stem
True
Short function: eye movement
How does the superior oblique move the eye?
Inferiorly and laterally

The trochlea (trochle = pulley) is a pulleylike loop through which the tendon of the superior oblique muscle passes
Identify the 3x CNs that innervate extrinsic muscle of the eye
TOA ( 3, 4, 6)
Following a moving object with the eyes assesses which cranial nerve(s)?
3, 4, and 6 since all three innervate extrinsic muscles of the eye
The oculomotor, trochlear, ophthalmic, and abducens nerves transit the ___ ___ ___
Superior Orbital Fissure
What is the largest of the cranial nerves that provides sensory neurons to face, head, and anterior 2/3 tongue?
5 - Trigeminal

- Emerges from pons isolated from other cranial nerves
- Motor neurons control chewing movements
What is the short function for CN 5?
- Mastication
- Facial sensation
What are the 2x trigeminal roots?
1.) Smaller motor root
- Supplys the muscles of mastication
2.) Larger sensory root
- Has three branches
What are the 3x branches for the larger sensory root on the trigeminal root?
- Ophthalmic nerve
- Maxillary nerve
- Mandibular nerve
Identify CNs
How do you assess CN 5 (Trigeminal)?
An assessment of motor function is to have the patient bite down while feeling the masseter muscle, then to have the patient attempt to open their mouth against resistance applied by the examiner
What is the assessment for sensory function of for CN 5 (Trigeminal)?
have the patient close their eyes, then the examiner touches the face with different objects (light pin touch, handle end of reflex hammer, Q-tip) and the patient describes the type of sensation as sharp, dull, soft, etc., the degree of pressure, and where it is on the face
Cranial nerve V is the ____for most of the skin of the face and scalp
Dermatome
Which cranial nerve is mainly motor that innervates lateral rectus muscle of the eye?
6 - Abducens
- Nerve is also called the abducent
- Short function: eye movement
Which muscle moves the eye laterally?
The lateral rectus muscle

It causes abduction of the eye (movement away from the midline of the body), hence the name of the nerve that supplies it
Following a moving object with the eyes assesses cranial nerves ___ ___ __ since all three innervate extrinsic muscles of the eye
3, 4, 6

The oculomotor, trochlear, ophthalmic, and abducens nerves transit the superior orbital fissure
Which cranial nerve is mixed, has somatic motor axons innervate muscles of facial expression, and stylohyoid, posterior belly of digastric, and stapedius muscles?
7 - Facial

Parasympathetic axons extend to lacrimal glands, nasal glands, and saliva-producing sublingual and submandibular glands
CN 7 has sensory axons extend from ___ ___ in the anterior two-thirds of the tongue (the mobile tongue)
Taste buds
What is the short function for CN 7?
- Facial expression
- Taste
- Salivation
- Lacrimation
The CN 7 parasympathetic axons extend where?
- Lacrimal glands
- Nasal glands
- Saliva-producing sublingual
- Submandibular glands*
How do you assess CN 7?
Having the patient exercise the muscles of facial expression by smiling, frowning and puffing both cheeks
- Noting asymmetries, drooping, sagging or smoothing of normal facial creases is an assessment of motor function
Which CN is mainly sensory, formerly known as the acoustic, or auditory nerve?
8 - Vestibulocochlear
Vestibular vs Cochlear branch in CN 8?
- Vestibular branch carries impulses for equilibrium
- Cochlear branch carries impulses for hearing
What is the short function for CN 8?
- Balance
- Hearing
How do you assess CN 8?
- Rub fingers together both alternately and simultaneously very near to, yet not touching, each ear as one assessment of hearing
Which CN is mixed, has sensory axons on the posterior one-third of the tongue for taste from taste buds, and for tactile sensation?
9 - Glossopharyngeal
What is the short function of CN 9?
- Taste
- Salivation
- Innervation of pharynx
How do you assess CN 9?
Having the patient open their mouth, protrude their tongue, and say "Ahh"
- Examiner observes the soft palate, uvula, and pharynx, as well as listens to the voice for evidence of hoarseness
- Is an assessment of both cranial nerves IX and X
The glossopharyngeal, vagus, and accessory nerves transit the ___ ___
Jugular foramen
Which CN is mixed and is the longest cranial nerve?
10 - Vagus
What is the short function for CN 10?
- Swallowing
- Talking
- Cardiac
- GI tract
- Respiration
- Taste
The vagus nerve is widely distributed where?
Head, neck, thorax, and abdomen
What is the sensory function of CN 10?
- Taste
- Touch
- Pain
- Temperature
- Proprioception from the epiglottis and pharynx; monitoring of blood pressure, oxygen, and carbon dioxide
What is the somatic motor function of CN 10?
- Swallowing
- Coughing
- Voice production
What is the autonomic motor function (parasympathetic) of CN 10?
In smooth muscle contraction and relaxation of GI tract
- Slowing of the heart rate
- Secretion of digestive fluids
Hyperactivity of the vagus nerves causes what?
Hypersecretion of acidic gastric fluids
- Results in ulceration of the stomach wall.

Patients with persistent and/or recurring ulcers can be treated with a selective vagotomy (partial severing of the right and left gastric nerves) to relieve this condition
The glossopharyngeal, vagus, and accessory nerves transit the ___ ___
Jugular foramen
Which CN is mixed, that originates from both the brain stem and the spinal cord, so it is sometimes called the spinal accessory (only cranial nerve to have a spinal cord component)?
11 - Accessory
CN 11 sends impulses to voluntary muscles used for what?
Swallowing,
- Also to trapezius and sternocleidomastoid
What is CN 11 short function?
- Pharynx & larynx muscles
- Neck & shoulder movement
The glossopharyngeal, vagus, and accessory nerves transit the ___ ___
Jugular foramen
Which CN is mixed, that innervates all intrinsic muscles of the tongue as well as all extrinsic tongue muscles except the palatoglossus, for movements in speech and swallowing?
12 - Hypoglossal
The palatoglossus is supplied by which CN?
10
What is the short function for CN 12?
Tongue movement
How do you assess CN 12?
Balanced action of the paired genioglossi muscles is required to protrude the tongue straight out.
- If one genioglossus muscle is inactive, the action of the intact muscle is unopposed. The tongue then deviates toward the side of the inactive muscle
What may result in fasciculation of the tongue muscle without atrophy of the tongue muscles on the affected side?
An upper motor neuron lesion (UMNL)

- In this case, the tongue deviates to the side opposite the lesion (because of crossing over).
What results in flaccid paralysis of the tongue with atrophy of tongue muscles on the affected side?
A lower motor neuron lesion (LMNL)

In this case, the tongue deviates to the same side as the lesion (crossing over is prior to the lower motor neuron).
The hypoglossal nerve penetrates the ___ ___
Hypoglossal canal
Identify
Identify