Neuro Chapter 17

Front 1

vestibular system

Back 1

primarily a reflex system that maintains the upright anatomical position

Front 2

maintenance of equilibrium

Back 2

three principal sources of sensory information:
1. vision
2. somatosensory (including position and touch)
3. vestibular apparatus of the internal ear
*balance can usually be maintained with 2/3 inputs

Front 3

vertigo

Back 3

dizziness (sensation of spinning or whirling motion), sometimes accompanied by nausea, vomiting, and pallor, caused by labyrinthine irritation

Front 4

Meniere's disease

Back 4

recurrent vertigo with tinnitus (sensation of noises in the ears) and deafness caused by complex pathology leading to degeneration of vestibular and cochlear hair cells

Front 5

stria vascularis

Back 5

produces endolymph in the cochlear duct, important for proper function of vestibular and cochlear receptors

Front 6

macula

Back 6

sensory epithelium found in the utricle and saccule

Front 7

vestibular hair cells

Back 7

sensitive mechanoreceptors located w/in cristae ampullares and maculae.
stereocilia extend from surface of hair cell.
kinocilium=single, eccentrically placed especially long cilium arising from centriole.
deflection of stereocilia toward kinocilium=increased depolarization in hair cell firing

Front 8

crista ampullaris

Back 8

stereocilia protrude into gelatinous cupula, sensitive to kinetic (rotary or angular) movement

Front 9

macula utriculus

Back 9

sensory hair cells oriented in the horizontal plane (sensitive to linear acceleration or deceleration), stereocilia protrude into otolithic membrane (contains crystals of calcium carbonate=otoliths)

Front 10

macula sacculus

Back 10

vertically oriented and sensitive to vertical movement

Front 11

vestibular (Scarpa's) ganglion

Back 11

located w/in internal auditory meatus, composed of bipolar neurons

Front 12

areas of brain contributing to the control of eye movements

Back 12

retina
cerebral cortex
cerebellum
superior colliculus

Front 13

Edinger-Westphal nucleus

Back 13

GVE innervation to ciliary ganglion, which in turn innervates the constrictor pupillae and ciliary muscles of the eye

Front 14

conjugate deviation

Back 14

rotation of the eyes equally and simultaneously in the same direction, problem=diplopia

Front 15

paramedian pontine reticular formation (PPRF)

Back 15

projects to the ocular nuclei via the MLF, stimulation results in horizontal eye movements

Front 16

ascending medial longitudinal fasciculus

Back 16

contains crossed and uncrossed projections originating from abducens, trochlear, and oculomotor nuclei, the PPRF, and vestibular nuclei.
crossed ascending from vestibular nuclei have excitatory effects, uncrossed have inhibitory effects

Front 17

vestibuloocular reflexes (VOR)

Back 17

eyes reflexively move in direction opposite of head movement, absence indicates brain stem damage

Front 18

superior colliculus

Back 18

receives afferents from retina, inferior colliculus, and cerebral cortex.
tectospinal and tectoreticular tracts...mediate orienting (startle) response, turning of head and eyes and raising of arms to an unexpected visual or auditory stimulus

Front 19

saccades

Back 19

voluntary, rapid, ballistic eye movements made to turn eye toward objects in periphery of visual field, controlled by cerebral cortex or superior colliculus

Front 20

tracking or smooth pursuit movements

Back 20

"locking" eyes onto a perceived moving object, involves the occipital eye field. movements voluntary, but cannot be done in the absence of visual stimuli

Front 21

vergence

Back 21

reflex convergence or divergence of the eyes in order to focus on objects moving toward or away from the viewer, controlled by occipital cortical projections to the superior colliculus

Front 22

nystagmus

Back 22

oscillating eye movements, slow and fast component (described in terms of fast component)

Front 23

lateral gaze paralysis

Back 23

results from lesion to abducens nucleus=inability to move both eyes to side of lesion because lesion disrupts connections between the abducens and oculomotor nucleus

Front 24

anterior internuclear ophthalmoplegia

Back 24

due to MLF lesion rostral to abducens nucleus=inability to move affected eye medially, horizontal nystagmus present in opposite abducting eye, commonly found in MS patients