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Chapter 27
The Cranial Nerves
127
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Undergraduate 3
09/14/2015

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Term
_____ fibers supply skeletal muscles, while _____ fibers supply smooth muscles & glands & belong to the parasympathetic part of the autonomic nervous system
Definition
somatic efferent; visceral efferent
Term
_____ fibers conduct sensory signals from the skin & mucous membranes of the face, from muscles & joints, & from the vestibular apparatus & the cochlea, while _____ fibers bring sensory signals from the visceral organs
Definition
somatic afferent; visceral afferent
Term
In early embryological development, the _____ form longitudinal columns, each column giving origin to only one of the four kinds of fiber
Definition
cranial nerve nuclei
Term
The cranial nerve nuclei & the cranial nerves are links in various _____
Definition
brain stem reflexes
Term
2 types of fibers that bring innervation from the motor cortical areas to the somatic motor nuclei
Definition
1. pyramidal tract (collaterals)
2. corticobulbar (destined only for the brain stem)
Term
ascending sensory tracts
Definition
how the somatic sensory nuclei convey signals to the sensory areas of the cerebral cortex
Term
4 kinds of fibers of the cranial nerves
Definition
1. somatic efferent
2. visceral efferent
3. somatic afferent
4. visceral afferent
Term
efferent fibers
Definition
fibers in the cranial nerves that have their cell bodies in brain stem nuclei corresponding to the columns of spinal motoneurons & the intermediolateral cell column of the cord
Term
2 types of efferent cranial nerve nuclei
Definition
1. somatic efferent
2. visceral efferent
Term
ganglia
Definition
where the afferent fibers have their cell bodies; close to the brain stem & corresponding to spinal ganglia
Term
2 types of afferent cranial nerve nuclei
Definition
1. somatic afferent
2. visceral afferent
Term
How are the somatic efferent nuclei arranged in early embryonic life? Later in life?
Definition
early: all in a column close to the midline
later: move away in the ventrolateral direction
Term
general somatic efferent (location of nuclei)
Definition
the nuclei remaining in the medialmost column; nucleus of the accessory nerve, nucleus of the hypoglossal nerve, nucleus of the abducens nerve, nucleus of the oculomotor nerve
Term
myotome muscles
Definition
muscles that are developed from the segmentally arranged somites of early embryonic life; innervated by general somatic efferent nuclei
Term
branchial muscles
Definition
striated muscles developed from the branchial arches; innervated by the somatic efferent nuclei that have moved away from the medial column
Term
visceral efferent (location of nuclei)
Definition
column of cranial nerve nuclei located immediately lateral to the somatic efferent column; (dorsal) motor nucleus of the vagus, small inferior & superior salivatory nuclei, parasympathetic oculomotor nucleus of Edinger-Westphal
Term
visceral afferent fibers (location of nuclei)
Definition
all end in one long nucleus (solitary nucleus) which is located lateral to the visceral afferent column
Term
What is the most lateral group of cranial nerve nuclei?
Definition
somatic afferent nuclei
Term
What nerve is classified as special somatic afferent? General somatic afferent?
Definition
special: vestibulocochlear (originated from special sense organs)
general: trigeminal
Term
How does the corneal reflex start?
Definition
afferent fibers of the trigeminal nerve enter at the midpontine level, descend in the brain stem, & form synapses in the lower medulla
Term
The cranial nerves are the first links in sensory pathways corresponding to the _____ & the _____
Definition
dorsal-column medial lemniscus system; spinothalamic pathway
Term
As the nuclei involved in the sensory pathways conducting from the spinal cord, those of the brain stem are subjected to _____ of the sensory transmission
Definition
descending control
Term
What types of cranial nerves are influenced by the pyramidal tract (fibers forming in the corticobulbar tract)?
Definition
somatic efferent cranial nerve nuclei
Term
Why is examination of the cranial nerves of great importance in clinical neurology?
Definition
it can provide exact information about the site of a disease process
Term
cranial nerve 12 (hypoglossal nerve)
Definition
motor nerve of the tongue
Term
The hypoglossal nerve is composed of only what type of fibers?
Definition
somatic efferent fibers
Term
hypoglossal nucleus
Definition
a slender, longitudinal column close to the midline in the medulla where the fibers for the hypoglossal nerve come from
Term
How do root fibers travel in the brain stem?
Definition
pass ventrally & leave the medulla just lateral to the pyramid
Term
hypoglossal canal
Definition
in the occipital bone where the small fiber bundles join to form the hypoglossal nerve & leave the skull
Term
Are the muscles of the tongue used voluntarily?
Definition
yes! during speech & eating
Term
Do reflex movements occur in the tongue?
Definition
yes! in swallowing
Term
Why does the tongue deviate to the paretic side when it is stretched?
Definition
paresis of the genioglossus muscle
Term
cranial nerve 11 (accessory nerve)
Definition
brings somatic efferent fibers to two muscles in the neck (sternocleidomastoid & trapezius)
Term
jugular foramen
Definition
where the accessory nerve leaves the skull together with the vagus & glossopharyngeal nerves
Term
Paresis of what muscles are generally observed in central motor lesions?
Definition
contralateral sternocleidomastoid & trapezius
Term
Because of the superficial position of the accessory nerve, it may be damaged in the _____ of the neck, producing a peripheral paresis
Definition
lateral triangle
Term
What is a special characteristic of cranial nerve 10 (vagus nerve)?
Definition
it contains fibers from all four kinds
Term
2 swellings of the vagus nerve in the jugular foramen & just below that contain the pseudounipolar cell bodies of the sensory vagus fibers
Definition
1. jugular ganglia
2. nodose ganglia
Term
The neurons leading from the CNS to the ganglia are called _____, & those leading from the ganglion to the organ are called _____
Definition
preganglionic; postganglionic
Term
The vagus gives off visceral efferent fibers descending to the _____ in the neck
Definition
heart
Term
Vagus nerve postganglionic visceral efferent fibers in the _____ determine heart rate
Definition
sinus node
Term
3 places that branches from the vagus nerve supply information to
Definition
1. esophagus
2. trachea
3. bronchi of the lung
Term
3 places in the abdomen where the vagus nerve sense fibers
Definition
1. stomach
2. small intestine
3. first half of the large intestine
Term
3 places that the vagus nerve supplies parasympathetic fibers
Definition
1. liver
2. gallbladder
3. pancreas
Term
Do signals in the vagus nerve reduce heart rate, constrict bronchi, & increase bronchial secretion whereas peristaltic movements & secretion are increased in the stomach & intestine?
Definition
yes!
Term
All of the sensory fibers from the larynx & some from the pharynx follow the _____ nerve
Definition
vagus
Term
2 nerves that the sensory fibers of the larynx follow
Definition
1. superior laryngeal nerve
2. recurrent laryngeal nerve
Term
On an embryological basis, how should all sensory fibers from the pharynx be categorized?
Definition
visceral afferent
Term
Do visceral afferent signals in the vagus nerve contribute to feelings such as hunger?
Definition
yes!
Term
Does the vagus nerve have an association with sickness behavior?
Definition
yes!
Term
The visceral afferents in the vagus nerve are links in reflex arc that control _____ & _____ of the gastrointestinal tract
Definition
secretion & peristaltic movements
Term
Vagus nerve reflexes mediate alterations of _____ & of ______ by changing the tone of the bronchial smooth muscles
Definition
airway secretion & airway resistance
Term
Where are the vagus nerve reflex centers located?
Definition
in the medulla (efferent links are visceral efferent fibers coming from the dorsal motor nucleus of the vagus)
Term
Visceral afferents from _____ in the wall of the large vessels provide information about the blood pressure in the aorta
Definition
baroreceptors
Term
Is the stimulation of taste receptors an example of a conditioned response or an unconditioned response?
Definition
unconditioned response
Term
ambiguus nucleus
Definition
where the somatic efferent vagus fibers come from; belongs to the special somatic efferent nuclei
Term
Where does the cricothyroid muscle receive motor fibers from?

*it is an example of a laryngeal muscle located on the outside
Definition
superior laryngeal nerve
Term
What nerve innervates the levator veli palatini muscle?
Definition
vagus
Term
What would happen if the vagus nerve was lesioned above the exit of the motor branches to the pharynx & the soft palate?
Definition
deviation of the uvula & the posterior pharyngeal wall to the normal side
Term
What tract influences the nucleus ambiguus during speech?
Definition
pyramidal tract
Term
What nucleus is involuntarily activated by the cough reflex?
Definition
nucleus ambiguus
Term
What cranial nerve resembles the vagus but is smaller & innervates a more restricted region?
Definition
cranial nerve 9 (glossopharyngeal)
Term
2 places innervated by the glossopharyngeal nerve
Definition
1. pharynx (muscles & mucous membrane)
2. taste buds (posterior)
Term
Does the glossopharyngeal nerve contain visceral efferent fibers?
Definition
yes! to the parotid gland & to the salivary glands in the posterior part of the tongue
Term
What type of fibers come from the carotid sinus?
Definition
a special group of visceral afferent fibers in the glossopharyngeal nerve
Term
Where do glossopharyngeal afferent fibers that end in the solitary nucleus get conveyed to?
Definition
motor nucleus of the vagus
Term
Does the glossopharyngeal nerve have something to do with blood pressure?
Definition
yes!
Term
The _____ fibers of the glossopharyngeal nerve to the striated pharynx muscles come from the ambiguus nucleus, whereas the _____ fibers have their cell bodies in the small inferior salivatory nucleus
Definition
somatic efferent; visceral efferent
Term
otic ganglion
Definition
where the preganglionic parasympathetic fibers from the inferior salivatory nucleus end just outside the cranial cavity (for the glossopharyngeal nerve)
Term
auriculotemporal nerve
Definition
a trigeminal branch that the postganglionic fibers from the ganglion cells join to reach gland; passes close to the otic ganglion (for the glossopharyngeal nerve)
Term
Where do the visceral afferent fibers of the glossopharyngeal nerve carrying signals from the taste buds in the posterior third of the tongue end?
Definition
solitary nucleus
Term
Where do the sensory fibers of the glossopharyngeal nerve from the posterior part of the tongue, the tonsils, the soft palate, & the pharynx end?
Definition
sensory trigeminal nucleus
Term
What cranial nerve is associated with the internal acoustic meatus?
Definition
vestibulocochlear nerve
Term
cerebellopontine angle
Definition
where the vestibulocochlear nerve enters the brain stem; at the lower end of the pons
Term
vestibular nuclei
Definition
where most fibers in the vestibular nerve end (some end in the cerebellum though)
Term
cochlear nuclei
Definition
where the cochlear nerve ends
Term
The cell bodies of the primary afferent fibers of the vestibular & cochlear nuclei are located at the bottom of the internal meatus, forming the _____ & the _____
Definition
vestibular ganglion & spiral ganglion
Term
Does the facial nerve contain special somatic efferent fibers?
Definition
yes!
Term
The small _____ follows the facial nerve & is usually considered to belong to it
Definition
intermediate nerve
Term
Does the facial nerve contain visceral efferent fibers?
Definition
yes!
Term
stylomastoid foramen
Definition
where the facial nerve leaves the skull; immediately medial & anterior to the mastoid process
Term
3 glands where the intermediate nerve brings secretory signals through its visceral efferent fibers
Definition
1. lacrimal gland
2. submandibular salivary gland
3. sublingual salivary gland
Term
Where do the visceral afferent fibers of the intermediate nerve come from?
Definition
the taste buds in the anterior 2/3 of the tongue
Term
facial nucleus
Definition
where the motor fibers of the facial nerve have their cell bodies; in the lower pons
Term
genu of the facial nerve
Definition
formed by the fibers passing medially & lying dorsally to the abducens nucleus; bends in the lateral & ventral direction
Term
facial colliculus
Definition
a small elevation formed when the facial fibers pass just beneath the floor of the fourth ventricle
Term
pyramidal tract
Definition
conveys signals for voluntary movements of the facial muscles
Term
How would a lesion of the pyramidal tract affect the facial nerve?
Definition
it would result in clear-cut paresis in the lower part of the face on the opposite side
Term
How would a peripheral lesion affect the facial nerve?
Definition
it would result in paresis of all the facial muscles on the same side as the lesion
Term
Bell's palsy
Definition
peripheral facial paresis; the cause is unknown
Term
Spontaneous facial expressions are most likely controlled by descending connections from the _____ & possible the _____
Definition
hypothalamus & basal ganglia
Term
What is the result of central paresis of the facial nerve?
Definition
emotional facial expressions are exaggerated (ex. a patient cannot suppress smiling or crying)
Term
How does Parkinson's disease reveal itself?
Definition
emotional, spontaneous expressions are lacking, whereas a voluntary, social smile is possible; disease of the basal ganglia; opposite effects of central paresis of the facial nerve
Term
What nerve mediates the stapedius reflex (contraction of the tiny stapedius muscle in the middle ear)
Definition
facial nerve
Term
hyperacusis
Definition
hypersensitivity to sounds; can be produced by peripheral facial paresis
Term
What fibers mostly make up the 5th cranial nerve (trigeminal nerve)?
Definition
somatic afferent fibers
Term
Does the trigeminal nerve contain special somatic efferent fibers?
Definition
yes!
Term
3 places that the trigeminal nerve conducts signals from in the face & the mucous membranes of the face
Definition
1. low-threshold mechanoreceptors
2. thermoreceptors
3. nociceptors
Term
Fibers from proprioceptors end in the _____, fibers from low-threshold mechanoreceptors end in the _____, whereas signals from nociceptors end in the _____ (for the trigeminal nerve)
Definition
mesencephalic nucleus; principle nucleus (main nucleus); spinal trigeminal nucleus
Term
Fibers from the main nucleus of the trigeminal nerve join the _____
Definition
medial lemniscus
Term
2 reflexes controlled by the trigeminal nerve
Definition
1. sneeze reflex
2. sucking reflex
Term
What reflex is monosynaptic & involves the mesencephalic trigeminal nucleus?
Definition
masseter reflex
Term
How can you detect a unilateral paresis of the masticatory muscles (controlled by the trigeminal nerve)?
Definition
ask the patient to open his mouth widely & the lower jaw deviates toward the side of the paretic muscles
Term
lateral pterygoid muscle (controlled by the trigeminal nerve)
Definition
pulls the mandible forward in conjunction with opening of the mouth
Term
Voluntary movements of the jaws during speech & chewing depend on the _____
Definition
pyramidal tract
Term
3 times reflex movements of the masticatory muscles occur
Definition
1. swallowing
2. sucking
3. vomiting
Term
What 3 cranial nerves supply the extraocular muscles with somatic efferent fibers?
Definition
1. abducens (cranial 6)
2. trochlear (cranial 4)
3. oculomotor (cranial 3)
Term
Which nerve contains visceral efferent fibers to the smooth, intrinsic eye muscles?
Definition
oculomotor nerve
Term
3 symptoms of lesions to the extraocular muscles
Definition
1. strabismus
2. double vision
3. dizziness
Term
What 3 nerves pass through the cavernous sinus before entering the orbit through the superior orbital fissure?
Definition
1. abducens nerve
2. trochlear nerve
3. oculomotor nerve
Term
lateral rectus
Definition
the only muscle supplied by the abducens nerve
Term
Where does the trochlear nucleus lie?
Definition
a little ventrally to the aqueduct in the mesencephalon
Term
superior oblique muscle
Definition
innervated by the trochlear nerve; directs the gaze downward & laterally
Term
Where do the somatic efferent fibers of the oculomotor nerve come from?
Definition
the large oculomotor nucleus situated close to the midline in the mesencephalon, ventral to the aqueduct
Term
Where do the visceral efferent fibers of the oculomotor nerve come from?
Definition
the small nucleus of Edinger-Westphal located near the oculomotor nucleus
Term
4 muscles innervated by the somatic efferent fibers of the oculomotor nerve
Definition
1. superior rectus
2. inferior rectus
3. medial rectus
4. inferior oblique
Term
levator palpebrae
Definition
the muscle supplied by the oculomotor nerve that serves to lift the upper eyelid
Term
Where do the visceral efferent fibers of the oculomotor nerve end?
Definition
the small ciliary ganglion situated behind the eye
Term
2 muscles innervated by the visceral efferent fibers of the oculomotor nerve
Definition
1. pupillary sphincter
2. ciliary muscle
Term
What results from a lesion of the oculomotor nerve?
Definition
an abnormal position of the eye, which is directed laterally & downward
Term
ptosis
Definition
an upper eyelid drooping due to paresis of the levator palpebrae
Term
What results from an interruption to the parasympathetic fibers of the oculomotor nerve?
Definition
making the pupil larger & a loss of the light reflex, loss of accommodation of the lens (impossible to see near objects sharply)
Term
Where is the light reflex's reflex center?
Definition
in the brain stem
Term
What does unilateral interruption of the oculomotor nerve result in?
Definition
a loss of the light reflex in the eye on the side of the lesion (the reflex is present in the other eye)
Term
What does interruption of the afferent link in the oculomotor nerve result in?
Definition
loss of light reflex in both eyes when light is shone into the eye on the lesioned side (light reflex is present in both sides when the other eye is illuminated)
Term
Where does the accommodation reflex arc pass through?
Definition
the cerebral cortex (it is a cortical reflex)
Term
What happens to the pupil in the eye as objects come closer?
Definition
it is constricted (accommodation reflex)
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