Flashcards in PPT 2: Vestibular Deck (29)
Where is the vestibular system located?
Within petrous portion of temporal bone
Endolymph or Perilymph?
A. Secreted by cochlear duct
B. Secreted by periosteum
C. Drains into dural sinuses via its lymphatic duct
D. Drains into CSF via its lymphatic duct
What is the Bony Labyrinth? What are its parts?
What is the Membranous Labyrinth? What are its parts?
Membranous tube containing receptors for head movement/position
Semicircular ducts (w/in semicircular canals)
Saccule & Utricle (w/in vestibule)
What is Meniere's disease? What causes it?
Transient vertigo, dizziness, nausea, vomiting, abnormal saccadic eye movements (nystagmus).
Excess endolymph secretion and fluid pressure affect receptor functions.
Endolymph or Perilymph?
A. Fills utricle, saccule, semicircular canals
B. Rotation of ducts with head movement causes flow of
C. Most sensitive to angular acceleration.
T or F? Crista
A. Receptors in the the ampulla of each semicirc. canal
B. Cupula cells make up a gelantinous mass
C. Hair cells have several kinocilium and one stereocilia that project into the cupula
D. When head rotates, cupula is displaced by movement of endolymph
B. False. Receptor (hair) cells and supporting cells make up gelatinous mass (cupula)
C. False. One kinocilium and several stereocilia
Fill In: Macula
A. Saccule & utricle contain _______ (receptor system)
B. Made of hair cells, gelatinous matrix, ____ and _____.
C. Top layer is ______ stones in gelatinous layer.
D. Kinocillum and stereocilia penetrate into _______.
B. Otolithic membrane and otoliths
C. Calcium carbonate stones
D. Gel layer
To what structures do the vestibular nuclei project vestibular information?
Thalamus and cortex
Spinal cord for postural control
Brain stem nuclei for eye movements
Autonomic centers for vascular control.
Fill In: Vestibulo-ocular reflex (VOR)
A. Adjusts _____ to rotation of head to fix gaze on object
B. Head rotation causes ___ eye movement for tracking
C. Rightward rotation of head stimulates _____ ducts.
D. Vestibular n. stimulates path to ___ n. and _____ (via reticular formation) to divert eyes to the left
A. eye movements
C. horizontal semicircular ducts
D. abducens nerve and oculomotor nuclei
Nystagmus: Physiological or Pathological?
A. Involuntary saccadic movements of eyeball
B. Occur when eyeball is moving
C. Spontaneous, when eye is at rest
D. Independent of head movements
What does the vestibule-sympathetic reflex (VSR) do?
Vasoconstriction to protect against syncope during postural changes or emotional stress. Increases skin vasoconstriction and sweating during nausea (sea sickness).
How does vestibular information get to the cortex?
Vestibular nuclei --> thalamus --> vestibular cortex
T or F: Vestibule-sympathetic reflex (VSR)
A. MAP goes up via vestibular mediated vasoconstriction
B. Cerebral blood flow increased by vasodilation of b.v.
C. Parasymp. inhibition of vasoconstriction via RVLM
D. Solitary nucleus (parasympathetic) vasodilates cerebral arteries
A. True. And baroreceptor
C. False. Sympathetic
D. False. Pterygopalatine ganglion vasodilates cerebral arteries
How does endolymph move?
As skull turns, endolymph maintains position due to inertia and creates a relative motion between bone and fluid. (soup in bowl)
What is detected by the semicircular ducts? How is this information communicated?
Differential fluid flows in all three ducts.
Hair cells trigger action potentials in vestibular n. Vestibular activity conveys net direction of head.
Fill In: Macula
A. When otoliths move it will bend ______ and ______.
B. Sensory neurons innervate ______ cells.
C. When cilia of hair cells bend _____ are generated
D. _____ acceleration distorts hair cells via otoliths, w/o endolymphatic movement
A. Gelatinous mass and microvilli of hair cells
B. Hair cells (receptor)
C. Receptor potentials
Fill In: Saccule and Utricle?
A. Saccule is oriented ____, utricule is _____
B. Each hair cell responds optimally to acceleration in the direction of _______
C. Stimulus to ______ triggers receptor potentials
A. Saccule = vertically, utricle= horizontally
B. Its alignment
C. Otoliths (which bend cilia of hair cells through the gel)
Sensory neurons from ________, ________, and _______ converge to form the vestibular n. which becomes part of CN____.
Semicircular canals, saccule, and utricle.
Part of Vestibulocochlear nerve (CN VIII)
T or F? Accoustic neuromas
A. Cause contralateral deafness or tinnitus.
B. Cause vestibular disturbance (unstable,vertigo, N/V)
C. Auto-immune reaction affecting inferior vestibular n.
A. False. Ispilateral.
C. False. Benign tumor of the myelin-forming cells of....
What causes benign paroxysmal positional vertigo?
Otoliths (otoconia) from utricle fall into semicircular canals and trigger apparent motion from the crista. Otolith dislodgement can be due to head injury, infection, or degeneration with age. Conflict of sensory input produces the apparent shift in position and body motion.
What is the role of the Vestibulo-Cerebellum (flocculonodular lobe)?
Sends processed info. back to vestibular nuceli. Facilitates vestibular reflexes.
What structures may be damaged in pathological nystagmus?
One or more components of the vestibular system, ie semicircular canals, utricle, saccule, or vestibule-cerebellum
How does the cerebellum impact the VOR?
Requires vestibule-cerebellum for precision.
How is otolith activity related to the vestibulo-sympathetic reflex (VSR)?
In order to increase MAP, increased otolithic activity after standing increases sympathetic activity to blood vessels in skeletal muscle and kidney, but not in GI.
Where is the vestibular cortex? How does it relate to other sensory modalities?
Parietal association and insular regions, including
(1) TPJ (temporal parietal junction)
(2) PIVC (Parietal-insular-vestibular cortex) = Parietal areas 2V, 3aV, and 7 and Insula
Autoscopic hallucination, Heautoscopy, or Out-of-Body?
A. See one's own body from an elevated perspective; w/disembodiment
B. See a double of yourself but w/o disembodiment
C. See double of oneself, uncertain if self is physical or autoscopic body.
D. Vestibular dysfunction in TPJ
A. Out of body
T or F: Vestibular Cortex
A. PIVC involved w/ sense of embodiment (self localized in one's physical body)
B. Unified picture of self; body, personal space
C. Conflict among sensory inputs --> illusions/delusions
A. False. TPJ does this.