Topic 8.6 Flashcards
3 modalities of the vestibular system
- gravity
- linear head movement
- head rotation
What are the sensory receptors of the vestibular system?
the hair cells
What type of cells are the hair cells? (2)
- mechanoreceptors
- modified epithelial cells
How many steriocilia are on the hair cells?
50-150
Type of filament in kinocilia / stereocilia
kino : microtubule
stero : actin
What is the vestibule?
The vestibular portion of the membranous labyrinth of the inner ear
5 structures of vestibule
- 2 otolithic organs
- 3 semicircular canals
What are the 2 otolithic organs?
utricule and saccule
Function of otolithic organs
Detection of gravity and linear head movement
What are the otolithic organs filled with?
endolymph
What are the dark cells?
Vestibular epithelial cells
What is the role of the dark cells?
Secretion of K+ into the endolymph
How are the hair cells in the utricular macula?
- horizontally oriented
- point towards the striola
How are the hair cells in the saccular macula?
- Vertically oriented
- Point away from the striola
What is the macula?
Structure that contains the hair cells and supporting cells
What do the stereocilia of the hair cells project into?
Into the gelatinous otolithic membrane
What is the otolithic membrane made of?
mass of mucopolysaccharides that has otoliths (CaCO3)
What happens when there is mvmt to the otolith membrane?
the inertia of the otoliths causes the membrane to move and deflect the stereocili
Afferentation of the otolithic organs
- vestibular nerve (CNVIII)
- scarpa’s ganglion
- type I axon
- ipsylateral vestibular nucleus (midbrain)
Efferentation of the otolithic organs
- vestibular nucleus
- type II axon
- scarpa’s ganglion
- vestibular nerve
Function of semilunar canals
detect head rotation (angular acceleration)
What is the sensory region of the semilunar canals?
The ampulla
What is the cupula?
mucopolysaccharide gel, without otoliths
Main difference between otolith membrane and cupula
the otolith is denser than endolymph but cupula has the same density
What is delay of rotation?
When endolymph’s acceleration equalizes with the rate of rotation of the semicircular canals
Reflexes related to the vestibular system
- vestibulospinal
- vestibulo-ocular
What is vestibular nystagmus?
uncontrolled eye movement due to dysfunction of the vestibular labyrinth
What are the primary taste qualities? (5)
- bitter
- salt
- sweet
- sour
- umami
What determines the flavor of a testant?
Both taste and smell
What is gustatory disfunction called?
ageusia
Where are the taste receptors located?
in the papillae, on the dorsal surface of the tongue
3 mechanisms for taste transduction
- tastant passes directly through ion channel (salt)
- tastant binds to ion channel (sour)
- tastant binds to membrane receptors that open channels (sweet, bitter, umami)
Which ion and channel for salt tasting?
- Na+
- ENaC
Which ion and channel for sour taste?
- H+
- TRPP3
Which molecule and receptor for bitter taste?
- toxins
- TAS2R
Which molecule and receptor for sweet taste?
- sugar
- TAS1R2 + TAS1R3 dimer
Which molecule and receptor for umami taste?
- Amino acids
- TAS1R1 + TAS1R3 dimer
What type of protein is gasducin?
Gq type protein
Which cranial nerves relay taste information?
- CN VII
- CN IX
- CN X
Which brain structures process taste information? (3)
- anterior insula
- frontal operculim
- postcentral gyrus
What type of cells are the olfactory receptors?
bipolar neurons
What is the olfactory epithelium made of?
- olfactory receptor cells
- support cells (kinda like glia)
- basal cells
What is the role of the odorant binding proteins?
help facilitate the diffusion of odorants in the mucus
What is the odorant receptor coupled to?
golf protein, Gs type protein
What does cAMP bind to in olfactory transduction?
cAMP gated cation channel
What does [Ca] increase lead to in olfactory transduction?
opening of Ca activated Cl- channels (outwards)
What is a big difference of the olfactory pathway compared to other pathways?
it does not have an obligatory synaptic relay in the thalamus
Where is the initial synapse of the olfactory pathway located?
in the olfactory bulb
3 structures in the olfactory bulb
- mitral cells
- inhibitory interneurons : granule cell, periglomerular cell
- glomeruli
Role of the granule cells
Form dendrodentritic reciprocal synapses with the mitral cells to enhance stimulus contrast and provide adaptation mechanism
Where do the axons of the mitral cells go to?
Anterior olfactory nucleus
Where does the lateral olfactory stria go?
primary olfactory striae
Where does the medial olfactory stria go?
To the amygdala
