Cranial Nerves Flashcards
1
Q
Name the twelve cranial nerves.
A
- On Old Olympus’ Towering Top, A Fin And* German Viewed A Hop
- olfactory (I), optic (II), oculomotor (III), trochlear (IV), trigeminal (V), abducens (VI), facial (VII), auditory* (VIII), glossopharyngeal (IX), vagus (X), accessory (XI), hypoglossal (XII)
- *auditory = vestibulocochlear
2
Q
Where is the nucleus of each cranial nerve found?
A
- cranial nerves I and II are in the forebrain
- midbrain: nuclei of cranial nerves III and IV
- pons: nuclei of cranial nerves V, VI, VII, and VIII
- medulla: nuclei of cranial nerves IX, X, XI (central portion), and XII
- spinal cord: nuclei of cranial nerve XI (spinal portion)
3
Q
What is unique about cranial nerve I?
A
- (the olfactory nerve)
- it is the only cranial nerve that does not communicate with the thalamus (so there is no thalamic relay to the cortex with this nerve)
4
Q
What are the functions of cranial nerves I, II, III, and IV?
A
- I (olfactory): smell (SENSORY)
- II (optic): sight (SENSORY)
- III (oculomotor): eye movement (MR, IR, SR, IO), pupillary constriction, accommodation, eyelid opening (MOTOR)
- IV (trochlear): eye movement (SO) (MOTOR)
5
Q
What are the functions of cranial nerves V, VI, VII, and VIII?
A
- V (trigeminal): mastication, facial sensation, somatosensation from anterior 2/3 of tongue (BOTH)
- VI (abducens): eye movement (LR) (MOTOR)
- VII (facial): facial movement, taste from anterior 2/3 of tongue, lacrimation, salivation (submandibular and sublingual), eyelid closing, stapedius muscle of ear (BOTH)
- VIII (vestibulocochlear): hearing, balance (SENSORY)
6
Q
What are the functions of cranial nerves IX, X, XI, and XII?
A
- IX (glossopharyngeal): taste and somatosensation from posterior 1/3 of tongue, swallowing, salivation (parotid), monitoring carotid body and sinus chemoreceptors and baroreceptors, stylopharyngeus muscle (BOTH)
- X (vagus): taste from epiglottic region, swallowing, uvula, soft palate, coughing, thoracoabdominal viscera, monitoring aortic arch chemoreceptors and baroreceptors (BOTH)
- XI (accessory): head turning, shoulder shrugging (MOTOR)
- XII (hypoglossal): tongue movement (MOTOR)
7
Q
Which cranial nerves are motor nerves? Which are sensory nerves? Which are both?
A
- Some Say Marry Money, But My Brother Says Big Brains Matter Most
- sensory: cranial nerves I, II, VIII
- motor: cranial nerves III, IV, VI, XI, XII
- both: cranial nerves V, VII, IX, X
8
Q
Which cranial nerves supply autonomic innervation? Which are parasympathetic and which are sympathetic?
A
- cranial nerves III, VII, IX, and X
- they are all parasympathetic (sympathetic innervation of head and neck comes from ascending fibers originating from T1/T2)
9
Q
Where do taste afferent fibers terminate? What else terminates here?
A
- taste afferents terminate in the medulla, at the nucleus solitarius
- visceral afferents also terminate here
10
Q
Cranial Nerve III
A
- oculomotor nerve; motor and parasympathetic
- contains the majority of somatic fibers for the extraocular muscles (SR, IR, MR, and IO)
- contains the preganglionic parasympathetic fibers innervating the smooth muscle of the eye (the sphincter pupillae muscle of the iris)
- elevates, depresses, and adducts the eyeball; manages the pupillary light and accommodation reflexes
- passes through the superior orbital fissure
11
Q
Cranial Nerve IV
A
- trochlear nerve; strictly motor
- contains the somatic fibers for the SO extraocular muscle
- depresses, abducts, and intorts the eyeball
- the only CN that emerges from the dorsal aspect of the brainstem
- passes through the superior orbital fissure
12
Q
Cranial Nerve VI
A
- abducens nerve; strictly motor
- contains the somatic fibers for the LR extraocular muscle
- abducts the eye
- passes through the superior orbital fissure
13
Q
What happens with a CN III lesion? a CN IV lesion? CN VI?
A
- CN III (oculomotor): ptosis, dilation of pupil, loss of light and accommodation reflexes, eye looks down and out
- CN IV (trochlear): eye moves upward, diplopia
- CN VI (abducens): diplopia, inability to abduct eye (can’t look out)
14
Q
Cranial Nerve V
A
- trigeminal nerve; motor and sensory
- contains sensory afferents from its ophthalmic, maxillary, and mandibular branches
- contains somatic fibers involved in mastication and tensor tympani
- main sensory nerve for the head, involved in corneal reflex (sensory part), and jaw jerk reflex
15
Q
Cranial Nerve VII
A
- facial nerve; motor, sensory, and parasympathetic
- lateral root contains sensory fibers to anterior 2/3 of tongue + outer ear and parasympathetic fibers to submandibular and sublingual salivary glands
- medial root: contains somatic fibers involved in facial expression (corneal reflex - motor part) and to the stapedius
- passes through the internal acoustic meatus
16
Q
Cranial Nerve VIII
A
- vestibulocochlear nerve; strictly sensory
- 2 parts: vestibular nerve (balance) and cochlear nerve (auditory stimuli)
- pass through the internal acoustic meatus
17
Q
Cranial Nerve IX
A
- glossopharyngeal nerve; motor, sensory, and parasympathetic
- contains sensory afferents from pharynx, posterior 1/3 of tongue, middle ear, and the chemoreceptors located in the carotid body and baroreceptors in the carotid sinus
- contains motor fibers to the stylopharyngeus muscle (for swallowing)
- contains parasympathetic fibers to parotid salivary glands
18
Q
Cranial Nerve X
A
- vagus nerve; motor, sensory, and parasympathetic
- contains sensory afferents from pharynx, larynx, esophagus, tympanic membrane, chemoreceptors in aortic bodies and baroreceptors in aortic arch, and thoracic and abdominal viscera
- contains motor fibers to soft palate, pharynx, larynx, and upper esophagus (these arise from nucleus ambiguus)
- contains parasympathetic fibers to viscera
19
Q
Cranial nerve XI
A
- accessory nerve; strictly motor
- cranial component carries motor fibers to soft palate, pharynx, and larynx (these arise from nucleus ambiguus)
- spinal component carries motor fibers to sternomastoid and trapezius (these arise from neurons in the anterior horns of cervical vertebrae)
20
Q
Cranial Nerve XII
A
- hypoglossal nerve; strictly motor
- contains motor fibers to the tongue
21
Q
What is the nucleus solitarius? The nucleus ambiguus?
A
- these are vagal nuclei
- nucleus solitarius deals with all visceral sensory information (taste, baroreceptors, gut distension, etc.); CNs VII, IX, and X project here
- nucleus ambiguus deals with the motor innervation of the pharynx, larynx, and upper esophagus (swallowing); CNs IX, X, and XI project here
22
Q
What is cavernous sinus syndrome? Which cranial nerves can be affected?
A
- a S.O.L. of the cavernous sinus (mass effect, fistula, thrombosis, etc.) that results in ophthalmoplegia (weak eye muscles) and decreased corneal and maxillary sensation (visual acuity is unaffected)
- this is due to the structures that pass through this sinus being compressed: CNs III, IV, V (V1 and V2), and VI
23
Q
What are common cranial nerve lesions? What are the clinical findings of each?
A
- CN V (trigeminal): jaw deviates TOWARDS the lesion because of unopposed force from the opposite pterygoid muscle
- CN X (vagus): uvula deviates AWAY from lesion
- CN XI (accessory): weakness when turning head to opposite side (this involves the ipsilateral sternocleidomastoid) and shoulder droop of the affected side
- CN XII (hypoglossal): tongue deviates TOWARDS lesion due to weakened tongue muscles on the affected side (the tongue is pushed, not pulled, out)
24
Q
Explain the major clinical difference between a pseudobulbar palsy and a bulbar palsy.
A
- pseudobulbar palsy (lesion of the corticobulbar tract; UMN lesion): results in contralateral facial paralysis, with SPARING of the forehead
- bulbar palsy (lesion of the facial nucleus or of CN VII; LMN lesion): results in contralateral facial paralysis without sparing of the forehead
- this occurs because the forehead actually has bilateral corticobulbar (UMN) innervation!
