Exam 3

Question 1

what are the 12 cranial nerves?

Answer 1

CN I: Olfactory
CN II: Optic
CN III: Oculomotor
CN IV: Trochlear
CN V: Trigeminal
CN VI: Abducens
CN VII: Facial
CN VIII: Vestibulocochlear
CN IX: Glossopharyngeal
CN X: Vagus
CN XI: Spinal Accessory
CN XII: Hypoglossal

Question 2

which cranial nerves are sensory, motor, or both?

Answer 2

CN I Olfactory: Some
CN II Optic: Say
CN III Oculomotor: Marry
CN IV Trochlear: Money
CN V Trigeminal: But
CN VI Abducens: My
CN VII Facial: Brother
CN VIII Vestibulocochlear: Says
CN IX Glossopharyngeal: Bigger
CN X Vagus: Brains
CN XI Spinal Accessory: Matter
CN XII Hypoglossal: Most

Question 3

where are somatic/visceral and sensory/motor nuclei located on the spinal cord?

Answer 3

somatic sensory: lie at the very top of the central canal, most lateral once the fourth ventricle splits
visceral (autonomic) sensory: lie right above the sulcus limitans, medial to the somatic sensory once the fourth ventricle splits
visceral (autonomic) motor: lies right below the sulcus limitans, lateral to the somatic motor once the fourth ventricle splits
somatic motor: lies at the very bottom of the central canal, most medial once the fourth ventricle splits
(diagram on L11S4)

Question 4

where are the two additional somatic/visceral and sensory/motor nuclei located on the brainstem?

Answer 4

branchial motor/branchiomeric or pharyngeal: between visceral motor and somatic motor in medial section
special sensory: lateral to somatic sensory in lateral section
(diagram on L11S4)

Question 5

what separates motor and sensory nerve nuclei?

Answer 5

the sulcus limitans

Question 6

which cranial nerve nuclei contain which cranial nerves?

Answer 6

somatic sensory: V
visceral (autonomic) sensory: VI, IX, X
visceral (autonomic) motor: X
somatic motor: III, IV, VI, XI, XII
special sensory: VIII
pharyngeal or branchiomeric: V, VII, X, XI

Question 7

where does CN I (olfactory) originate and terminate?

Answer 7

originate in the olfactory bulb and terminate in the olfactory epithelium

Question 8

where does CN II (optic) originate and terminate?

Answer 8

originate in lateral geniculate nucleus, superior colliculus, and hypothalamus and terminate in retinal ganglion cells

Question 9

where does CN III (oculomotor) originate and terminate?

Answer 9

originates in the oculomotor nucleus in the midbrain and terminates at 4 of the 6 eye muscles (medial, superior and inferior recti, and inferior oblique)

Question 10

where does CN IV (trochlear) originate and terminate?

Answer 10

originates in the trochlear nucleus in the midbrain and terminates at superior oblique muscle, fibers originate on contralateral side

Question 11

where does CN V (trigeminal) originate and terminate?

Answer 11

main sensory nerve of the head (tactile, pain, temp, proprioception), originate and terminate in the: mesencephalic nucleus -> the muscle spindles and other mechanoreceptors
spinal and main sensory nucleus -> skin, deep tissues, and dura of the head
motor nucleus: masseter muscle

Question 12

where does CN VI (abducens) originate and terminate?

Answer 12

originates in the abducens nucleus in the pons and terminates in the lateral rectus, contain interneurons that project to contralateral oculomotor nucleus via medial longitudinal fasciculus

Question 13

where does CN VII (facial) originate and terminate?

Answer 13

originate from facial motor nucleus and terminate in muscles of facial expression, stapedius

Question 14

where does CN VIII (vestibulocochlear) originate and terminate?

Answer 14

originate from cochlear and vesticular nuclei and terminate in the organ of corti, cristae of semicircular ducts, maculae of utricle and saccule

Question 15

where does CN IX (glossopharyngeal) originate and terminate?

Answer 15

visceral sensory fibers from oral cavity and somatic sensory fibers from middle ear originate in inferior salivatory nucleus
motor fibers originate in the nucleus ambiguous and terminate in the pharynx (stylopharyngeus muscle)

Question 16

where does CN X (vagus) originate and terminate?

Answer 16

main parasympathetic nerve that originate from dorsal motor nucleus of vagus beneath the vagal trigone and terminate in the thoracic and abdominal viscera

Question 17

where does CN XI (accessory) originate and terminate?

Answer 17

originate in accessory nucleus in caudal medulla/upper 5 cervical vertebrae and terminates in neck and shoulder muscles (sternocleidomastoid and trapezius)

Question 18

where does CN XII (hypoglossal) originate and terminate?

Answer 18

originates in hypoglossal nucleus of medulla (under the hypoglossal trigone) and terminates in the tongue muscles

Question 19

what eye movement disorders result from damage to the left abducens nerve (left lateral rectus)?

Answer 19

results in abducens palsy
gaze right: normal
gaze straight: medial strabismus
gaze left: strabismus is worse

Question 20

what eye movement disorders result from damage to the left abducens nucleus (right medial rectus and left lateral rectus)?

Answer 20

results in lateral gaze paralysis
gaze right: normal
gaze straight: medial strabismus
gaze left: paralysis of gaze to left

Question 21

what eye movement disorders result from damage to the left MLF (left medial rectus)?

Answer 21

results in internuclear ophthalmoplegia
gaze right: paralysis of left medial rectus, only right eye moves
gaze left: normal

Question 22

what eye movement disorders result from damage to the left abducens nucleus and MLF?

Answer 22

gaze right: only right eye move
gaze straight: medial strabismus
gaze left: paralysis of gaze to left, only left eye moves

Question 23

what do lesions to the CN XII hypoglossal nerve cause?

Answer 23

cause atrophy of tongue muscle ipsilateral to lesion site and cause deviation of the tongue towards the lesioned side

Question 24

how does upper motor neuron damage affect facial regions differently?

Answer 24

upper facial muscles get bilateral innervation by CN VII, but lower face only gets contralateral innervation by CN VII nuclei in the brainstem before they combine in the cortex, if the lesion is in the cortex then you will see lower facial paralysis, if the lesion is only in the brainstem then there will be defecits on the lesion side of the head and the opposute side of the body (damage before the fibers cross)
(diagram on L11S32-33)

Question 25

where are taste buds located and what innervates them?

Answer 25

foliate papillae: located on the back lateral sides of the tongue, innervated by CN VII and IX fungiform papillae: located on the front of the tongue, innervated by CN VII circumvallate papillae: located on the top back of the tongue, behind fungiform, innervated by CN IX epiglottis: located in the throat, innervated by CN X CN V and IX are responsible for general sensation of the tongue (V: front of tongue and roof of mouth, IX: back of tongue and throat)

Question 26

what are the transduction mechanism for the different flavors?

Answer 26

salty: Na+ ions through Na+ channels and other nonselective cation channels sour: weak acids diffuse across membrane to acidify cytoplasm and open cation channels, strong acids open pH sensitive cation channels sweet/bitter/umami: tastants bind to G protein-coupled receptors, dissociation of G protein activates phospholipase yielding IP3 and DAG, and increase in intracellular Ca2+, which triggers opening of Ca 2+ -gated cation channels

Question 27

what is the taste (gustatory) pathway?

Answer 27

1st order afferents from cranial nerves VII, IX, X synapse in brainstem (NTS), 2nd order NTS neurons project either: through central tegmental tract to ventral posteromedial nucleus of the thalamus and then to the gustatory cortex to dorsal motor nucleus of the vagus and reticular formation for reflex activity (diagram on L14S6)

Question 28

how are odorants detected?

Answer 28

olfactory receptors are located on olfactory receptor neurons in the olfactory epithelium, they detect odors and transmit signal via CN I, CN I travels through cribriform plate to reach olfactory bulb

Question 29

what is the arrangement of the olfactory system?

Answer 29

axons from bipolar neurons that express a single receptor type project from the olfactory epithelium to a single glomerulus in the olfactory bulb, each glomerulus contains dendrites from mitrial cells (form the olfactory tract), tufted cells and granule cells (diagram on L14S14-15)

Question 30

where does the olfactory tract project to?

Answer 30

- anterior olfactory nucleus on to contralateral olfactory bulb - olfactory cortex (piriform cortex) but without passing through thalamus - amygdala and periamygdaloid cortex - parahippocampal gyrus

Question 31

where does the olfactory/piriform cortex project to?

Answer 31

- thalamus - sensory association areas - orbital cortex (along with gustatory)

Question 32

what is the anatomy of the auditory system?

Answer 32

receptor cells are hair cells (abundant outer hair cells but fewer inner hair cells) attached to the basilar membrane in the membranous labyrinth which is located within the bony cochlea (bony labyrinth), the bony labyrinth is filled with perilymph and the membranous labyrinth is filled with endolymph, hair cell activation results from movement of the basilar membrane (diagram on L12S4)

Question 33

how does cochlear division of CN VIII convey sound information?

Answer 33

1st order neurons in spiral ganglion (mostly inner hair cells) travel to 2nd order neurons in cochlear nuclei, some cross in pons in trapezoid body and travel on both ipsilateral and contralateral sides in lateral lemniscus to inferior colliculus, from inferior colliculus (of both sides) to thalamus (medial geniculate nucleus) which projects to auditory cortex via internal capsule (diagram in Lab Quiz 7 Practice slides)

Question 34

how do inner and outer hair cells differ?

Answer 34

inner hair cells are sensory outer hair cells act as amplifier (add energy) which yields auto acoustic emissions

Question 35

what do results of the rinne test mean?

Answer 35

normally, air conduction is better than bone conduction, if bone conduction is more efficient then there is conductive hearing loss, if air conduction is more efficient and hearing is decreased in the affected ear then there is sensorineural hearing loss (diagram on L12S17-18, be able to interpret audiogram)

Question 36

what do results of the weber test mean?

Answer 36

if tuning fork sounds louder in the affected ear then there is conductive hearing loss in the affected ear if tuning fork sounds louder in the good ear then there is sensorineural hearing loss in the affected ear (diagram on L12S17-18, be able to interpret audiogram)

Question 37

what are the major balance receptors?

Answer 37

semicircular canals are comprised of ampulla (location of hair cells (made up of crista on bottom and cupula on top)) that detect rotational head movements specifically, tilting forward or backwards macula of saccule and macula of utricle are otoliths that are sensitive to linear and vertical acceleration

Question 38

how does the vestibular division of CN VIII convey information about balance?

Answer 38

inputs to vestibular nuclei from: - utricle, saccule, ampullae - other vestibular nuclei - spinal cord outputs from vestibular nuclei to: - cerebellum - spinal cord (via MLF) (lateral vestibulospinal tract and medial vestibulospinal tract) - cranial nerve nuclei (III, IV, VI) (crossed and uncrossed via MLF) - thalamus (bilaterally to cortex)

Question 39

what is the vestibuloocular reflex?

Answer 39

semicircular canals detect rotation -> vestibular ganglion -> vestibular nuclei in brainstem -> through MLF to CN III to innervate medial rectus or through CN VI to innervate lateral rectus, this allows eyes to move in opposite direction of head movement to stay fixed on target (called nystagmus)

Question 40

how does pathological nystagmus occur?

Answer 40

lateral medullary syndrome or posterior inferior cerebellar arteries (PICA) syndrome results when there is stroke damage to the lateral medulla, this causes pathological nystagmus