neuro 8.6 equilibrium taste smell Flashcards
(65 cards)
functions of vestibular system (4)
-sense of balance
-causes generation of muscle contractions
-cause of re-orientation of body (skeletal m.)
-controls eye movement
-for reflexes
2 types of reflex in vestibular system
-vestibulo-spinal
-vestibulo-ocular
what happens if disfunction in vestibular system
-results in vertigo
-means makes walking and standing become impossible
modalities that can be sensed (3)
-position of head
-linear acceleration of head
-rotation of head
vestibular hair cells
-hair cells are modified epithelial hair cells
-they secrete neurotransmitters
what neurotransmitters do vestibular hair cells secrete and function
-aspartate and mainly glutamate
-activate nerve cells
-depending on amount secreted, the AP frequency will be different
components of vestibular hair cells (2)
-1 kinocilium (a single, long cilium)
-50-100 stereocilia
2 types of vestibular hair cells
-type 1 - “real” receptors that detect stimuli
-type 2 - function not fully understood
resting membrane potential
-40mV
K+ in endolymph and perilymph
endolymph - high K+
perilymph - low K+
K+ in perilymph
3-3.8mM same as csf
location of production of endolymph
-generated from perilymph using transepithelial transport system
BASICALLY
-in stria vascularis of cochlea
mechanism of endolymph
-K+ transported from perilymph to endolymph that creates fluid (endolymph)
where will the endolymph fill
vestibular system even tho its far from cochlea
2 things that happen after endolymph fills vestibular system
-K+ conc stays the same
-from -80mV to 0 mV
reason for drop of electrical potential in vestibular endolymph from cochlear endolymph
-distance too large
-potential becomes attenuated
how is the movement of stereocilia
-stereocilia are connected via tip links (thin filaments) which are responsible for synchronised movement of stereocilia
mechanic-electrical transduction steps (4)
1-mechanical stimulus will cause movement of stereocilia
2-tip link (thin fila) tension increases due to this movement, results in conformation change of proteins
3-mechanosensitve channels are activated e.g TMC1 & TMC2 channels
4-K+ influx leads to depolarisation and activated of voltage-gated Ca2+ channels –> increase in [Ca2+]ic –> NT release
what are TMC1&TMC2 channels
and main effects
-non-specific cation channels that let K+, Na+, Ca2+ in
-main effect Is K+ influx creating K+ current
what happens if stereocilia move in opposite direction
-channels close
-cell hyperpolarizes
-no NT released
2 otolithic organs and location
-saccule and utricle
-near centre of membranous labyrinth
what fluid fills otolithic organs and what surrounds them
-filled by endolymph
-surrounded by perilymph
what does macula contain
hair cells
function of vestibular duct cells
secrete K+ ions into endolymph -like stria vascularis
