The Auditory System Flashcards
what is compressed air?
air with dense particles.
what is rarefied air?
air with less dense particles.
what is frequency (waves)?
no. of compressed and rarefied patches of air pass by our ears each second, (Hz).
what is low frequency?
fewer compressed and rarefied patches of air passing by our ears in a second.
what is high frequency?
more compressed and rarefied patches of air passing by our ears in a second.
what is intensity / amplitude (waves)?
the air pressure difference between peaks and troughs, (dB).
what is low intensity?
a small difference in air pressure between the peaks and troughs (a quiet sound).
what is high intensity?
a greater difference in air pressure between the peaks and troughs (a loud sound).
what is the outer ear made up of?
Pinna,
Auditory canal,
Tympanic membrane.
what is the middle ear made up of?
air-filled chamber,
Ossicles,
Oval window.
what is the inner ear made up of?
Vestibular portion,
Cochlea,
Vestibulocochlear nerve (cranial nerve 8).
what are the Ossicles?
the 3 tiniest bones in the body.
name the 3 Ossicles:
Malleus,
Incus,
Stapes.
what type of connection is between the Malleus and the Incus?
a rigid connection,
when the Malleus moves, the Incus moves.
what type of connection is between the Incus and the Stapes?
a flexible connection,
when the Incus moves, the Stapes moves which causes the Oval window to move in and out.
describe the process of the inward movement of the Tympanic membrane by the compression phase of a sound wave:
pushes the Malleus downwards,
the Incus moves up,
pushes the Stapes into Oval window,
fluid moves into the Cochlea.
describe the process of the outward movement of the Tympanic membrane by the rarefaction phase of a sound wave:
moves Malleus into horizontal position,
moves Incus along with it,
pulls Stapes out so fluid moves outwards towards the middle ear.
what is the overall shape of the cochlea / the drawn shape?
has a base and then it loops round like the spirals on a snail shell.
how many fluid filled compartments are there in the cochlea?
3.
what is the name of the fluid filled compartment that connects to the Oval window and runs all over the cochlea?
the Scala Vestibuli.
what is the name of the other compartment that allows fluid to move in and out as it is being pushed by the Oval window?
the Scala Tympani.
what is the name of the third compartment that is filled with endolymph?
the Scala Media.
which 2 compartments are filled with perilymph?
the Scala Vestibuli and the Scala Tympani.
how are the Scala Vestibuli and the Scala Tympani connected?
the helicotrema.
where is the Organ of Corti located?
it is between the Scala Media and the Scala Tympani.
what does the Organ or Corti contain?
hair cells.
where do the hair cells sit, and what are they covered by?
hair cells sit on the basilar membrane and are covered by the tectorial membrane.
what happens when fluid moves in and out of the Scala Vestibuli? (basic)
causes a ripple of movement in the Scala Tympani,
displacement of basilar membrane,
and hair cells to mechanically deflect (translated to electrical potentials in the cells).
what specific parts of the hair cells are moved / deflected by the basilar membrane displacement?
hair bundles.
describe the structure of the basilar membrane:
membrane is thinner, thicker in depth, and stiff at the base of the cochlea,
the membrane is wider and less stiff at the apex of the cochlea.
different frequencies of sound will displace the basilar membrane to different extents:
high frequencies causes displacement at the base of the membrane,
whereas low frequencies cause displacement at the apex.
how does the basilar membrane displacement affect hair cells? (rarefaction)
as the stapes move outwards,
the membrane moves upwards,
the tectorial membrane moves in one direction,
moves the hair bundles towards the longer stereocilia,
initiating depolarisation in the hair cells.
how does the basilar membrane displacement affect hair cells? (compression)
as the stapes move inwards,
the membrane moves downwards,
the tectorial membrane is pulled in the other direction towards shorter stereocilia,
initiating hyperpolarisation.
what structure connects the hair cells?
tip links.
what happens to the tip links when the hair bundles are pushed and pulled?
the tip links mechanically open the channels to the hair cells causing K+ ions from the endolymph to enter.
describe the process that occurs when the hair bundles are pushed towards the longer bundles:
the tip links tighten and the channels open,
K+ enters the cell increasing the positivity of the cell,
graded potential travels from the apex of the cell to the base of the cell,
causes Ca2+ channels to open,
Ca2+ causes the exocytosis / fusion of glutamate vesicles at the base of the cell.
describe the process that occurs when the hair bundles are pushed towards the shorter bundles:
the tip links slacken and the channels close,
K+ cannot enter the cell so the cell becomes more hyperpolarised,
Ca2+ cannot enter the cell,
not glutamate released,
no firing of the afferent neuron.
