24/ the auditory system

Question 1

frequency def

Answer 1

• number of compressed or rarefied patches of air that pass by our ears each second
• hertz , Hz

Question 2

intensity/amplitude

Answer 2

• air pressure dif between peaks and troughs
• decibels, dB - logarithmic scale

Question 3

human hearing range

Answer 3

20 Hz - 20,000 Hz

Question 4

outer ear anatomy

Answer 4

• pinna - involved in ability to locate sounds in the vertical plane
• external auditory canal

Question 5

middle ear anatomy

Answer 5

• ossicles: malleus, incus, staples (touching oval window)
• tympanic membrane: ear drum. transfer sound from middle ear to inner ear, moves back and forward, fluid up and down

Question 6

inner ear anatomy

Answer 6

cochlea

Question 7

how does the middle ear transfer sound

Answer 7

• ossicles amplify sound - exerts 20x more pressure on oval window than tympanic memb
• overcomes greater impedance of cochlear fluid

Question 8

where in the cochlear are higher and lower frequencies heard

Answer 8

• higher - base
• low - apex

Question 9

basilar memb in cochlea - how does it detect dif frequencies

Answer 9

• narrower and stiffer at the base - harder to move, high frequencies
• wider and floppier at apex (helicotrema) - easier to move, low frequencies
• displaced in a tonotopic manner

Question 10

anatomy of the cochlea

Answer 10

• scala vestibuli and scala tympani - perilymph
• scala media - endolymph
• organ of corti - hair cells found

Question 11

anatomy of organ of corti (cochlea) hair bundles

Answer 11

• hair cells have hair bundles at their apex
• inner hair cells = primary sensory receptors
• outer hair cells = cochlear amplifier
• 3 outer cair cells, 1 inner. outer hair cells make it easier for inner hair cells to detect lower intensity, inner essential

Question 12

where are hair bundles found, what are they made of, what are they linked by

Answer 12

• located at top part of hair cells
• made of stereocilia - 3 rows (not staircase)
• stereocilia connected by tip links
• mechanoelectrical transducer channel

Question 13

how does basilar movement displacement cause movement of hair bundles

Answer 13

• stapes move outwards
• bm moves upwards
• hair bundles pushed towards taller stereocilia
• tip links stretch
• and opposite

Question 14

how do inner hair cells function as primary sensory receptors

Answer 14

• basilar memb displaced
• hair bundles displaced
• MET channels open
• graded receptor potential develops in hair cell
• calcium enters hair cell through voltage gated channels
• glutamate released by hair cell
• epsp develops in afferent neuron
• AP develops in afferent neuron