Exam #6: Vestibular Function Flashcards Preview

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Flashcards in Exam #6: Vestibular Function Deck (26):

What is the utricle? What is the function of the utricle?

This is an otolith organ that contains a macula with hair cells
- Oriented horizontally
- Contains calcium carbonate crystals
- Respond to LINEAR motion


What is the saccule? What is the function of the saccule?

This is an otolith organ that contains a macula with hair cells
- Oriented vertically
- Contains calcium carbonate crystals
- Respond to LINEAR motion


What are the semicircular canals? What is the function of the semicircular canals?

- Vestibular organ containing hair cells that respond to ANGULAR acceleration
- Endolymph actually bends the stereocilia


What is the vestibular hair cell? What is the function of the vestibular hair cell?

- These are the sensory receptors of the vestibular system
- DEPOLARIZES when stereocilia bent TOWARD kinocilium
- HYPERPOLARIZES when stereo cilica bent AWAY


What is endolymph? What is the function of endolymph?

This is the fluid that fills the vestibular division of the membranous labyrinth


What is the vestibulo-ocular reflex in response to head tilt?

If the head is tilted to one side, the eyes rotate in the OPPOSITE direction

****This helps maintain the visual field in the horizontal plane


What is the vestibulo-ocular reflex in response to head turn?

If the head makes a small turn one direction, eyes turn the OPPOSITE direction

****This facilitates fixation on a distant target


What is post rotatory nystagmus. Explain why a patient shows post-rotatory nystagmus.

- Involuntary rhythmic oscillation of the eyes is called post-rotary nystagmus AFTER a patient stops spinning
- Inertia of the endolymph in the semicricular canal makes person think they are turning in the direction OPPOSITE to their initial turning


What is the "slow phase of (vestibular) nystagmus?"

Slow phase is the eye movement OPPOSITE to the direction of turning

*Think of the person trying to maintain gaze


What is the "fast phase of nystagmus?"

Fast phase is a rapid movement of the eyes back to midline after the slow phase

*Think of the eyes as "jumping ahead"


If a patient is in a coma can they exhibit both phases of nystagmus?

NO--they can have the slow phase, but not the fast phase

****Note that the mnemonic gives you the direction of the FAST phase, the slow phase (seen in comatose patient) will be OPPOSITE of the mnemonic for caloric testing


What are the directions for nystagmus during turning? After rotation?

During rotation=
- Slow= opposite
- Fast= same

Post rotation= person thinks he/she is turning opposite direction
- Slow= same
- Fast= opposite

*Note that nystagmus is named after the fast component of nystagmus


What is the probable cause of positional vertigo?

- Free-floating particles in the semicircular canals
- Specifically, part of an otoconium (Calcium carboante) that is detached from the utricle
- Detachment is caused by trauma or viral labyrinthitis


What are the symptoms of positional vertigo?

Episodic vertigo lasting ~40 seconds in different positions


What is the probable cause of Meniere syndrome?

Imbalance between the production and reabsorption of endolymph


What are the symptoms of Meniere Syndrome?

- Ear fullness/ pressure
- Decreased hearing
- Tinnitus
- Severe vertigo
- Nausea
- Vomiting

****Episodic attacks last minutes to hours at a time


Outline the vestibular pathway. What are the main inputs to the vestibular nuclei?

1) Some vestibular hair cells, terminate in vestibular nuclei in the MEDULLA
- Medial & superior nuclei= semicircular canals
- Lateral nucleus= utricle
- Inferior nucleus= utricle, saccule, & semicircular canals

2) Others project to the floculonodular lobe of cerebellum & then the cerebellum projects to vestibular nuclei


What are the main outputs of the vestibular nuclei? Assign a function to each output

1) Medial & superior vestibular nuclei synapse via the Medial Fongitudinal Fasciculus (MLF) to the extraocular muscles of the eye

2) Lateral vestibulospinal tract projects to motor neurons of limb & trunk (balance/ posture)

3) Medial vestibulospinal tract--neck muscles-->head position

4) Higher centers (thalamus & cortex)= awareness of body orientation & motion


What are the three major roles for the vestibular system? What sensory systems help the vestibular system fulfill these roles?

1) Awareness of body position in space
2) Postural tone & equilibrium
3) Stabilization of the eyes during head movement


What is the the doll's eye maneuver. When is it performed? What is being tested?

- This is a maneuver to evaluate brainstem function in an unconscious patient
- Hold eyes open and tilt head
- See SLOW phase OPPOSITE the direction of head turn


What is caloric testing of vestibular function? Describe the set-up for caloric testing of vestibular function.

- This is a test of vestibular function w/out turning the patient
- Cold or warm water irrigated in the ear can cause movement of the endolymph in semicircular canals via convection


In caloric testing of vestibular function, how do the eyes move if cold water is put in the ear canal? How do they move in response to warm water? What kind of eye movements would you see in a comatose patient?

COWS--mnemonic to name the FAST phase of nystagmus

Cold= opposite
Warm= same


If a patient is tested by turning to the left, what direction does he or she think they are turning after rotation?



After turning a patient to the left, what direction is slow phase post-rotary nystagmus?


*****Mnemonic for post-rotary nystagmus: after turning, SLOW phase is in the SAME direction as turning


After turning a patient to the left what direction is fast phase post-rotary nystagmus?


****The fast phase is always opposite of the previous turning movement


How is nystagmus named?

Direction of the fast phase

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