Lecture 6 Flashcards
(16 cards)
What 2 cranial nerves run through the internal auditory meatus
facial (7) and auditory (8) nerve
inner hair cell anatomy characteristics
Piriform (pear shape)
Same length the whole way along the cochlea
Outer hair cell anatomy characteristics
Cylindrical (long and skinny)
Different lengths along the cochlea
- longer in apex, shorter at base
Voltage motors along lateral walls
difference between innervation of the hair cells (terminal terminaton)
Outer hair cell: efferent and afferent terminals both synapse at the base
inner hair cell: afferent synapses at the base, efferent has an axodendritic synapse onto the afferent dendrite. This is so it can modulate activity of the hair cell
How do ions move into hair cells
tip links
shearing force
Stereo cilia are embedded in tectorial membrane
if sheering force is up and lateral, channels are pulled open
if sheeting force is down and medial, the channels wont open
Mechanoelectrical transduction (MET) channel
channel that hair cell transduction is done through
glutamatergic system
which hair cell is more depolarised and why?
the outer hair cells
because of voltage motors
voltage motors
activated when voltage inside the cell is changed (from lateral shearing force and ion influx)
causes prestin (motor protein in lateral walls of OHC) to contract when voltage changes
inner hair cell innervation
90% of afferent (sensory) dendrites
TYPE I afferent fibres
convergent innervation (1IHC : 20 afferent fibres)
efferent terminates of afferent
inner hair cell function
critical for sound transmission to the brain
OHC innervation
10% afferent dendrites
TYPE II afferent fibres
Divergent innervation (10-12 OHC: 1 afferent fibre)
Efferents have large direct contact with OHC (hence the brain is better at modulating activity in the OHC)
OHC function
Amplifier
Type I and Type II afferent fibre differences
Type I: large, myelinated, IHC
Type II: small, unmyelinated, OHC
origin of cochlea efferent neuron cell bodies
superior olivary complex (SOC) of the brain stem
MOC and LOCs
medial olivocochlear neurons synapse with 8th nerve adn terminate on OHC
lateral olivocochlear neurons synapse on the base of Type I dendrite under IHC
