7. Audition Flashcards
what is the major purpose of the vestibular system?
balance and movement
mechanoreceptors that respond to gravity, movement, vibration, and pressure
hair cells
where are hair cells found in fish/amphibians, and what do they do?
the lateral line, detect changes in vibrations and pressure
where are hair cells found in mammals, and what do they do?
the vestibular apparatus (gravity and movement), and the cochlea (sound)
detects movement of water, pressure changes, and vibrations; helpful for schooling behaviour and prey capture
the lateral line system
the anterior end of the lateral line evolved into the:
inner ear
true or false: all hair cell bundles contain a true kinocillium
false
what happens to the kinocillium during development of cochlear hair cells?
the kinocillium disappears
where in the cochlea are cilia the longest?
in the vestibular canals (high frequency sounds)
where in the cochlea are cilia shortest?
at the base of the cochlea (low frequency sounds)
sterocilia contain ____ to make them rigid, but bend at the base
actin
what makes kinocilium different from stereocilia?
they are taller and differ slightly in protein structure
connect the tops of each sterocilium with the adjacent larger cilium, and are aligned along the axis of the hair bundle
tip-links
do hair cells have axons?
no, but they release glutamate to sensory afferents
which neurotransmitter is released by hair cells?
glutamate
what type of synapses are associated with hair cells?
ribbon synapses
an ongoing relase of glutamate from hair cells is due to the actions of:
L-type Ca++ channels (long opening, little inactivation)
which neurotransmitter is associated with efferent inputs to hair cells?
acetylcholine
true or false: the efferent nerve fibers that synapse onto hair cells can be excitatory or inhibitory
true
what type of movement depolarizes hair cells?
movement toward the kinocilium
what type of movement hyperpolarizes hair cells?
movement away from the kinocilium
displacements as small as ____ can be detected?
1nm (causes 0.2mV change in the hair cell)
channels near the tip links which open as they stretch
mechanoelectrical transduction (MET) channels
when MET channels open, which cations open in order to depolarize the hair cell?
K+ ions
why is it that K+ depolarizes hair cells instead of hyperpolarizing them?
the cilia are found within the endolymph, which contains a high concentration of K+, thus K+ will rush into the hair cells when channels open
structure of the inner ear important for angular accelerations of the head (rotation)
semicircular canals
what are the two otolith organs?
the utricle and saccule
contain calcium carbonate crystals and are involved in linear accelerations of the head (including gravity)
otolith organs (utricle and saccule)
which of the otolith organs is aligned on the sagittal plane?
the saccule
which of the otolith organs is aligned on the horizontal plane?
utricle
how many types of vestibular hair cells are there?
two
an afferent nerve ending which encases type I hair cells?
calyx endings
