Vestibular System Flashcards
What kind of receptors are the hair cells in the vestibular cells?
mechanoreceptors that respond to gravity, movement, vibration, and pressure
What is a statocyst? What can it detect?
- small organ of balance and orientation in some aquatic invertebrates, consisting of a sensory vesicle or cell containing statoliths (sand or calcium carbonate)
- detect direction of gravity and direction of movement
What kind of system of hair cells do fish and aquatic amphibians have? What does this system detect?
lateral line system; detects movement of water, water pressure changes, vibrations
Which end of the lateral line evolved into the inner ear? What does the inner ear contain? What is the function of the inner ear?
- anterior end of lateral line
- contain vestibular apparatus and cochlear
- function = balance and audition
label the diagram of the inner ear
slide 6
TRUE or FALSE: kinocilia are larger than stereocilia
TRUE
How many kinocilia are there in a hair bundle? stereocilia?
- 1 kinocilium
- 40-70 stereocilia
Where are cilia longest? shortest?
- longest at vestibular canals
- shortest at base of cochlea
What makes stereocilia rigid but bend at the base?
actin
What are tip-links?
connect tops of each stereocilium with the adjacent larger cilium along the axis of the hair bundle (towards kinocilium)
What are lateral links?
connect neighbouring stereocilia so when one bends, the rest bend too
TRUE or FALSE: hair cells have axons and they release GABA to sensory afferents
FALSE: do NOT have axons; release GLUTAMATE
What kind of synapses do hair cells make?
ribbon synapses
What is a ribbon synapse?
on-going release of glutamate because of L-type Ca2+ channels, which are long-opening and have little inactivation
Do hair cells receive efferent inputs? If yes, what NT is used? Are the effects excitatory of inhibitory?
- yes, hair cells receive efferent inputs
- ACh
- excitatory AND inhibitory
TRUE or FALSE: hair cells work the same in lateral line, vestibular, and auditory systems
TRUE
TRUE or FALSE: movement toward the kinocilium depolarizes the hair cell. opposite movement hyperpolarizes the cell
TRUE
How are hair cells depolarized? Be specific.
- hair cell displaced towards kinocilium
- channels near tip-links open as they stretch (i.e. tip link pulls open ion channels)
What is the smallest displacement of hair cell that can be detected? How much of a depolarization does this cause in the hair cell?
- as small as 1 nm
- causes 0.2 mV change
How many MET channels are there per hair cell? How many channels per cilium?
- 100 channels per hair cell
- 1 or 2 channels per cilium
TRUE or FALSE: there are very few channels per cilium
TRUE
What kind of channels near tip-links open as they stretch?
mechanoelectrical transduction (MET) channels
label the diagram of tip link and hair cell on slide 13
slide 13
Draw a diagram to show the rat of action potentials sent to a primary sensory neuron when a hair cell is at rest, excited, and inhibited. Which way are the cilia pointed? how much glutamate is released? Also draw a diagram to show membrane potential of the hair cell.
slide 14
Which ions flow through MET channels to depolarize a hair cell? What direction?
K+ into cell
TRUE or FALSE: Na+ is responsible for depolarizing hair cells
FALSE: K+
TRUE or FALSE: the cilia are within the perilymph
FALSE: endolymph
What is special about the fact that cilia are within the endolymph?
very high K+ concentration in the endolymph; therefore large gradient causes K+ to flow through channels, into the hair cells
What role does Ca2+ play in hair cells?
Ca2+ enters cell at depol (along with K+) to allow vesicle fusion and release of NT
What do the semicircular canals detect?
angular accelerations of the head (rotation)
What do the otolith organs detect? What are the names for these organs?
- linear accelerations of the head (including gravity)
- utricle and saccule
The basilar papilla is to birds as the ____________ is to humans.
cochlea
On which plane does the saccle detect linear acceleration? utricle?
Draw a diagram and indicate which way the kinocilia point in relation to the striola for these two otolith organs.
- saccule = sagittal plane; away from striola
- utricle = horizontal plane; towards striola
What are the 2 types of vestibular hair cells? What is the main difference? What is the difference between their efferents and afferents? Draw a diagram and label the two
- type I hair cell: more stereocilia; afferent = calyx ending around the receptor; efferent synapses on the afferent
- type II hair cell: less stereocilia; afferent = bouton-type synapse on receptor; efferent synapses on receptor
(slide 20)
is ribbon synapse on both types of vestibular hair cells or only type I??
ask people
What are the 3 types of vestibular afferents? Where are they located? Why type of hair cell do they synapse on?
- calyx (type I); near striola
- bouton-type (type II); distant from striola
- dimorphic (type I and II); throughout macular surface
(see diagram on slide 21)
What is otoconia? Where is it found? How is it activated by linear accelerations like gravity?
- gelatinous mass of protein plus calcium carbonate crystals
- on top of otolith organs
- otoconia has INERTIA, thus, the hair cells in the utricle and saccule can be activated by linear accelerations like gravity
In what direction must the linear movement/translation of the head be in, in order to depolarize a hair cell? which way would the hair cell be moving? Draw a diagram to explain.
linear translation in the direction OPPOSITE the kinocilium will cause hair cells to bend TOWARDS kinocilium, leading to depolarization of the hair cell
(sldie 24)
In what direction must the head tilt in order to depolarize a hair cell, in relation to the kinocilium?
head tilt TOWARD kinocilium will depolarize the hair cell
label slide 26 and indicate which cell would be depolarized if a head moved in a certain direction
slide 26
Describe the orientation of the semicircular canals in relation to planes and midline.
- anterior canal = oriented in a vertical plane, 45 degrees to midline
- posterior canal = oriented in a vertical plane, 45 degrees to midline
- horizontal canal = oriented in the horizontal plane
Where are the hairs embedded in the semicircular canals? What causes this structure to move?
- cupula
- fluid and otoliths cause cupula to move
In a cupula, which wayare hair cells oriented?
all oriented in the same direction
In which direction does the cupula move in relation to head rotation and hair cells?
- cupula deflects in the opposite direction of the head rotation
- hair cells deflect in the same direction as the cupula deflection
What analogy is used to describe how semicircular canals work?
antagonistic push-pull pairs
TRUE or FALSE: leftward rotation of the head inhibits hair cells of the left horizontal canal and excites hair cells of the right horizontal canal
FALSE: leftward rotation, excite left horizontal canal hair cells, inhibit right hor. canal hair cells
TRUE or FALSE: rotation down-left about a horizontal axis ecites hair cells of the left anterior canal and inhibits hair cells of the right anterior canal
FALSE: inhibit right POSTERIOR canal
What is the vestibulo-ocular reflex (VOX)
eyes move in opposite direction of head
Starting from the afferents from teh semicircular canals, describe the pathway of the VOR. Specify which cranial nerve nuclei are involved.
- semicircular canal afferents
- synapse on vestibular nuclei
- VI, abducens nucleus
- III, oculomotor nucleus
- medial/lateral rectus muscles