Auditory & Vestibular Systems Flashcards
What are hair bundles filled with?
→ actin and are stiff rods
What do hair cells synapse onto?
→ Auditory nerve fibre that projects to the brain
What do hair cells convert?
→ Motion of stereocilia into release of neurotransmitter
→ NT is converted into electrical activity
What is the extracellular matrix of the hair cells called?
→tectorial membrane
Where is the otoconial membrane?
→ In the macula of the vestibular system
Where is the cupula?
→ Cristae of vestibular system
How are stereocilia arranged?
→ In bundles
What are stereocilia connected by?
→ connectors
What are the 3 types of connectors?
→ Top connector
→ Shaft connector
→ Ankle links
What connectors are important to transduction?
→ tip links
What is the function of lateral link connectors?
→ they hold the bundle of stereocilia together to allow it to move as a unit
What is the function of tip links?
→ Tension in the tip links distorts the tip of the stereocilia mechanically
→ distortion allows channels to open and close with cilia movement
→ current flows proportionately
Describe how hair cells work
→ Tip links open ion channels
→ outside the stereocilia is a fluid called endolymph
→ when tip links deform and pull on the top of the stereocilia they allow in a lot of K+
→ endolymph is high in K+
→ K+ influx depolarises the cell
→ VGCC opens
→ Ca2+ triggers neurotransmitter release at the synapse
→ postsynaptic potential in nerve fibre triggers an action potential
When does depolarisation occur?
→ When the hair bundle is pushed towards the tallest stereocilia
When does hyperpolarisation occur?
→ When the hair bundle is pushed away from the tallest cilia
What system do fish and amphibians have?
→ Lateral line system
What is the function of mechanoreceptors on fish?
→ Provides information about movement through water or the direction and velocity of water flow
How do neuromasts function?
→ Gelatinous cupula encases the hair bundle and moves in response to water motion
What is the inner ear formed from?
→ Semicircular canals from the vestibular system
→ Cochlea
Where do the afferent nerves come from?
→ Vestibulocochlear nerve CN VIII
What is linear motion?
→ Up, down
→ left and right
→ back and forwards
What is rotation?
→ Rolling - shoulder to shoulder
→ pitch - forwards and backwards
→ yaw - side to side
What senses rotation?
→ Semicircular canals
What is responsible for sensing roll?
→ Posterior semicircular canal
What is responsible for sensing pitch (y-axis)?
→ Anterior semicircular canal
What is responsible for sensing yaw?
→ Horizontal semicircular canal
Where does the endolymph move?
→ In the opposite direction to your head
What does rotation cause in the semicircular canals?
→ Fluid motion
What are cilia connected to?
→ Gelatinous cupula
Describe what happens in the cupula when motion occurs
→ Fluid in the canals lags due to inertia pulling the cupula in the opposite direction to the rotation of the head
→ cilia are displaced and depolarise hair cells
What is the ampulla?
→ AN opening with receptors
What does the cupula detect?
→ Flow of fluid through the semicircular canal