SDL Auditory System

Question 1

the lowest sound pressure a human can hear

Answer 1

2000 Hz

Question 2

humans can hear a sound at a different frequency other than 2000 Hz, but the sound intensity..

Answer 2

must be higher

Question 3

intensity equation

Answer 3

I = 20 log P/R

so, a sound that is 10 x louder is 20 dB louder

Question 4

sound pressure level of normal speech

Answer 4

60 dB

Question 5

what happens when sound enters the external auditory meatus?

Answer 5

it hits the tympanic membrane, which initiates the movement of ossicles

Question 6

where is the sound transmitted after relaying through the ossicles?

Answer 6

from the tympanic membrane to the oval window

Question 7

what is the significance of the tympanic membrane being larger than the oval window?

Answer 7

transforming a small force into a large one, called “impedance matching”. gives a 10-fold increase of force/area through this process

Question 8

the force of impedance matching is used to…

Answer 8

push perilymph in the inner ear

Question 9

muscles attached to ossicles, and that cranial nerves innervate them

Answer 9

tensor tympani - CN V

stapedius - CN VII

Question 10

function of tensor tympani and stapedius; what happens to hearing when CN VII is damaged?

Answer 10

reflex contraction of these muscles helps protect hearing apparatus during sustained loud sounds.

if CN VII is damaged, the stapedius will malfunction, and normal sounds will sound very loud AKA “hyperacusis”

Question 11

movement of perilymph waves from start to finish

Answer 11

immediately outside the oval window in the scala vestibule, around the helicotrema, and in the scala tympani (all in the cochlea)

Question 12

characteristics of endolymph and perilymph

Answer 12

endolymph: like intracellular fluid, high in K+
perilymph: like extracellular fluid, high in Na+

Question 13

the compartment filled with endolymph

Answer 13

cochlear duct (scala media)

Question 14

apparatus designed to detect sound//location

Answer 14

organ of Corti; sits inside the cochlear duct on the basilar membrane

Question 15

location of inner and outer hair cells and their function

Answer 15

sit on the basilar membrane and touch the tectorial membrane/ responsible for detecting sounds

Question 16

how is the sound wave (vibration) transformed to electric signals in the auditory system?

Answer 16

sound waves hit tympanic membrane, vibration transmitted into cochlea causing waves in perilymph/endolymph and movement of basilar membrane

hair cells move

stereocilia on top of hair cell touches tectorial membrane, bent toward one direction or another

this increases glutamate release from the hair cell while bending toward the other direction will decrease glutamate release

glutamate will activate the primary auditory neurons of the spiral ganglion. series of action potentials will then be initiated.

Question 17

the spiral ganglion receives most of the inputs from the..

Answer 17

inner hair cells; outer hair cells help increase sensitivity of the inner hair cells

Question 18

shape of the basilar membrane

Answer 18

narrow at the base, wide at the apex

Question 19

type of sound that moves through the apex of the basilar membrane (wider, more flexible)

Answer 19

low frequencies; hair cells are tuned to low frequencies here; apex=low tones

Question 20

the base of the basilar membrane is narrower and stiffer, equipped for..

Answer 20

higher tones

Question 21

loss of hair cells can be caused by..

Answer 21

excessive loud noise

aminoglycoside antibiotics toxicity - neomycin, kanamycin, streptomycin, gentamicin

Question 22

aminoglycosides can cause hair cell in which systems.

Answer 22

auditory and vestibular system

Question 23

how auditory info is sent to the brainstem

Answer 23

hair cells release glutamate, stimulates the primary auditory neurons of the spinal ganglion, info sent via the cochlear nerve, to the cochlear nuclei in the medulla

Question 24

once the auditory info enters medulla and goes beyond the cochlear nuclei, how does it ascend in the brainstem? what structure?

Answer 24

ascends bilaterally- the trapezoid body is a set of fiber bundles that transmits auditory signals from side to side.

Question 25

because of the bilateral distribution of fiber bundles that transmit auditory signals, a unilateral lesion of the brainstem..

Answer 25

does NOT cause apparent hearing deficit

Question 26

a lesion that occurs distal to the cochlear nuclei will cause..

Answer 26

ipsilateral hearing deficit

Question 27

the major fiber bundle ascending with the auditory info

Answer 27

lateral lemniscus

Question 28

major components of the auditory system, where they’re located

Answer 28

inferior colliculus (midbrain), medial geniculate nucleus (midbrain)

Question 29

the destination of auditory info

Answer 29

transverse temporal gyrus

Question 30

location of cochlear nucleus

Answer 30

medulla

Question 31

auditory pathway starting with organ of corti

Answer 31

organ of corti, spiral ganglion, cochlear nuclei, lat lemniscus, inferior colliculus, brachium, medial geniculate nucleus, internal capsule, auditory radiation, primary auditory cortex, transverse temporal gyrus, broadman’s area (41, 42)

Question 32

a structure that helps us to localize the source of a sound, from left or right side of the body

Answer 32

superior olivary nucleus

Question 33

how does the superior olivary nucleus localize sound from the left or right side of the body?

Answer 33

the sound going to the opposite side of the body’s ear will have a lower intensity; the superior olivary nucleus on the left and right sided pons will compare the sound info from each ear and determine the source of the sound

Question 34

structure that does selective attention of sounds in a setting with multiple noise levels going simultaneously; mechanism?

Answer 34

efferent cochlear bundle; signals from the superior olivary nucleus is rerouted to the organ of corti to suppress irrelevant auditory signals (normally info Is sent from organ of corti to superior olivary nucleus)

Question 35

what causes perilymph fistula?

Answer 35

a leak of perilymph through the oval window or round window; change in air pressure could aggravate this situation (flying, scuba diving)

Question 36

where in the brain is the auditory cortex?

Answer 36

transverse temporal gyrus Heschi

Question 37

tests used to determine conduction hearing loss or nerve hearing loss

Answer 37

Weber test, Rinne test

Question 38

what is the functional difference between lateral leminuscus and medial lemniscus?

Answer 38

lateral - auditory

medial - vision

Question 39

what is the difference between superior colliculus and inferior colliculus?

Answer 39

superior does vision, inferior does auditory

Question 40

difference between medial geniculate nucleus and lateral geniculate nucleus?

Answer 40

LGN - vision

MGN - auditory

Question 41

does the auditory pathway go through the thalamus?

Answer 41

yes

Question 42

which structures in the auditory pathway belongs to thalamus?

Answer 42

medial geniculate nucleus