Reading...
Play button
Play button
Use LEFT and RIGHT arrow keys to navigate between flashcards;
Use UP and DOWN arrow keys to flip the card;
H to show hint;
A reads text to speech;
72 Cards in this Set
- Front
- Back
|
What is the purpose of the vestibular system?
|
To respond to linear and angular accelerations of the head.
|
|
|
What does this acceleration information provide information about?
|
Head position and movement.
|
|
|
3 General Components of the Vestibular apparatus:
|
-Semicircular canals
-Fluids -Receptors |
|
|
What components of the vestibular apparatus tell the brain about LINEAR accelerations?
|
Utricle + saccule
|
|
|
In what position is the Saccule?
|
Dorsal-ventral
|
|
|
In what position is the Utricle?
|
Lateral
|
|
|
What component in both the utricle and saccule contains the receptors for detecting linear accelerations?
|
the MACULA
|
|
|
What components of the vestibular apparatus tell the brain about ANGULAR accelerations?
|
Semicircular canals
|
|
|
What component of the semicircular canals contains the receptors?
|
CUPULA
|
|
|
What are the receptors in the cupula and macula?
|
Hair cells
|
|
|
What are the receptive components of hair cells?
|
kinocilium - the tallest on the end
|
|
|
What happens when stereocilia are bent toward the kinocilia?
|
Depolarization of the hair cell
|
|
|
What happens if the stereocilia are bent away from the kinocilia?
|
hyperpolarization
|
|
|
What do the saccular and utricular maccules contain?
|
Otolith
|
|
|
What is otolith?
|
A heavy fluid (high specific gravity containing CaCO3
|
|
|
How does otolith achieve sensation of linear displacement?
|
When the head tilts, the heavy fluid is acted on by gravity so it flows over hair cells and bends them in a certain way.
|
|
|
What macular otolith responds to head tilting back/forth?
|
Saccule
|
|
|
What otolith/maccule responds to head tilting side to side?
|
Utricle
|
|
|
What layer over the hair cells moves simultaneously with otolithic displacement?
|
otoconia
|
|
|
In addition to telling about head accelerations what do the saccule and utricle detect?
|
Static positions of the head.
|
|
|
How many semicircular canals?
|
3 - lateral, anterior, posterior
|
|
|
Semicircular canals give information about:
|
Angular acceleration
|
|
|
Component of semicirc canals that contains receptors:
|
Cupula
|
|
|
What does the cupula contain?
|
-Hair cells
-Endolymph |
|
|
How does endolymph compare to otolith?
|
-Same sp gravity
-No CaCO3 |
|
|
What is the ampulla?
|
The interior of a canal
|
|
|
What happens to hair cells when bent forward?
|
Hyperpolarization
|
|
|
What happens to hair cells when they bend back?
|
Depolarization
|
|
|
What causes the hair cells in right lateral semicircular canals to move back?
|
Moving the head to the right
|
|
|
What is the effect on hair cells in the left lateral semicircular canals when you move your head to the right?
|
They move forward, so hyperpolarize.
|
|
|
So the initial response of endolymph to head movement is:
|
To resist movement due to its inertia.
|
|
|
What happens to endolymph as you keep moving your head?
|
it moves with your head.
|
|
|
What happens when you stop moving abruptly?
|
Endolymph Fluid continues to move but your head stops so hair cells hyperpolarize on right as they depolarize on left
|
|
|
What do we call it when you stop rotating to the right suddenly?
|
Left nystagmus
|
|
|
Pneumonic for nystagmus:
|
COWS
Cold = opposite nystagmus Warm = same nystagmus |
|
|
What does putting cold in the right ear do?
|
Causes right ear hair cells to hyperpolarize and left ear hair cells to depolarize - like you're turning to the left.
|
|
|
So the firing in the vestibular nerve fibers depends on:
|
The direction in which hairs are bent.
|
|
|
Result of bending hair cells toward the kinocilium:
|
Depolarization and increase rate of firing in afferents.
|
|
|
Bending away from the kinocilium:
|
Hyperpolarization and Decreased rate of firing in afferents.
|
|
|
Why do the vestibular hair cells allow sensation of static position?
|
Because they are constantly firing at rest.
|
|
|
How do the hair cells in the vestibular apparatus transmit their impulses to the CNS?
|
By releasing neurotransmitters in graded ways onto bipolar axons in the vestibular part of CN VIII
|
|
|
Where does the afferent information from hair cells go first?
|
To the vestibular ganglion
|
|
|
Where does info go from the vestibular ganglion?
|
Via central processes constituting CN VIII to the vestibular nuclei.
|
|
|
Where are the vestibular nuclei located?
|
In the medulla
|
|
|
What do the vestibular nuclei do with information about static postition and acceleration?
|
They DISTRIBUTE that information to a very widespread array of efferents in the neuraxis.
|
|
|
What makes the vestibular system unique?
|
It has a more widespread distribution of efferents in the neuraxis than any other special sensory system!
|
|
|
How many efferents do the vestibular nuclei have?
|
8 - EIGHT!!!
|
|
|
What is the function of the Vestibulospinal tract efferent?
|
To influence motorneurons to the EXTENSOR muscles (extend leg to catch your balance if you trip)
|
|
|
Why do vestibular nuclei have efferent motor neurons to innervate the neck muscles?
|
To coordinate head movments with the eyes moving.
|
|
|
How else do the vestibular nuclei control eye tracking?
|
By having efferents to the eye muscle nuclei.
|
|
|
How do the vestibular nuclei coordinate processing of vestibular information from both sides?
|
Both have efferents to each other
|
|
|
What vestibular efferent is employed when you nod your head in class and it wakes you up?
|
Reticular formation
|
|
|
What vestibular efferents allow conscious processing of vestibular input?
|
Thalamic projections to the cortex areas 3a and 2v
|
|
|
What role does the hypothalamic efferent of vestibular nuclei have?
|
Motion sickness
|
|
|
What IS nystagmus? (define)
|
Normal rythmic involuntary oscillations of the eyes - alternating slow and rapid OCULAR EXCURSIONs
|
|
|
2 types of nystagmus:
|
-Optokinetic
-Vestibular |
|
|
What is Optokinetic nystagmus?
|
That induced by moving stimuli across the visual field
|
|
|
What is vestibular nystagmus?
|
Nystagmus induced by MOVEMENTS OF THE HEAD.
|
|
|
How do the eyes move in vestibular nystagmus? Why?
|
Against the direction of head movmenet, to preserve gaze (keep it fixed).
|
|
|
What is the function of normal nystagmus?
|
To hold images steady on the retina while the body is spinning.
|
|
|
What is the purpose of the caloric test?
|
To test for unilateral vestibular function.
|
|
|
What is the basis of the caloric test?
|
Pouring cold water in a right ear that is tilted to 30' (to make the lateral canal horizontal) will cause nystagmus in the left direction.
|
|
|
What happens if you pour warm water in the right ear?
|
It causes nystagmus in the right direction.
|
|
|
What is the physical effect that causes nystagmus in caloric testing?
|
Convection currents
|
|
|
What would happen if the patient laid on his STOMACH and you did caloric testing?
|
Nystagmus would be OPPOSITE:
Cold - same direction Warm - opposite direction |
|
|
Why is nystagmus flipped when the patient lies on their stomach versus back?
|
Because convection currents are dependent on gravity
|
|
|
What if there were no gravity?
|
No nystagmus would be seen.
|
|
|
Why does drinking alcohol give the sensation of spinning?
|
ETOH has a light spcf gravity; when intake is excessive it gets into the endolymph; causes much more increased sensitivity to movements and takes longer for fluid to stop moving (less inertia).
|
|
|
What causes vertigo?
|
Damage to the vestibular apparatus on one side of the head.
|
|
|
What is vertigo?
|
Movement of the eyes ALONG WITH the head when it rotates due to lack of compensitory eye fixing.
|
|
|
How does the world appear to move in patients with vertigo?
|
Away from the side of the lesion
|
|
|
When patients with vertigo rotate to the left, what is their sense of rotation?
|
To the right.
|
