Ears

Question 1

What are the 3 parts of the ear?

Answer 1

outer, middle, inner

Question 2

Describe outer ear

Answer 2

pinna/auricle channels sound waves in to external auditory canal –> tympanic membrane –> eardrum vibrates

Question 3

Describe middle ear

Answer 3

Ossicles transmit and amplify vibrations to inner ear: malleus = affixed to eardrum –> acts on incus –> acts on stapes –> stapes rest on oval window of cochlea. Middle ear = connected to Eustachian tube - equalizes pressure b/w middle ear and environment, removes cellular and bacterial waste, drain fluid from middle ear to pharynx

Question 4

Describe inner ear

Answer 4

cochlea, vestibule (the bony labyrinth section containing utricles and saccules) and semicircular canal contain membranous labyrinth carrying endolymph. membranous labyrinth = suspended w/in bony labyrinth carrying perilymph. perilymph transmits vibrations from outside and cushions inner ear structures

Question 5

Describe the auditory pathway

Answer 5

pinna –> external auditory canal –> tympanic membrane –> malleus –> incus –> stapes –> cochlear oval window –> cochlear perilymph –> basilar membrane –> hair cells –> auditory/vestibulocochlear nerve –> brainstem –> MGN of thalamus –> auditory cortex of temporal lobe

Question 6

Loudness is perceived based on what 2 sound characteristics?

Answer 6

sound pressure and frequency

higher amp –> louder, and thus higher intensity (b/c intensity = proportional to amp^2)

Question 7

Describe anatomy of hair cells

Answer 7

rests on organ of Corti; top = hair bundle. Kinocilia = filaments that make up hair bundle, they’re connected by spring-like tip links. When hair cells move back and forth, tip link stretches –> K+ and Ca2+ channels open to allow K+ and Ca2+ to enter cell –> activates spiral ganglion cell –> sends signal to auditory nerve

Question 8

What’s place theory vs basilar tuning? Tonotypical mapping?

Answer 8

Idea that pitch is determined by location of cochlea vs when base of basilar membrane and close to oval window detects high freq and tip of basilar membrane and away from oval window detects low freq. Mapping where high and low freq sounds will be detected at level of temporal cortex

Question 9

What’s the main sensory organ for hearing (like the body’s microphone)? What are the 3 scalae in inner ear?

Answer 9

Organ of Corti - converts mechanical sound waves into electrical impulses; it lies w/ cochlea and is beneath inflexible tectorial membrane, made up of hair cells bathed in endolymph, and rests on flexible basilar membrane
Organ of Corti = in middle scala; 2 other scalae = filled w/ perilymph

Question 10

utricle & saccule vs semicircular canals

Answer 10

lie w/in vestibule, contain modified hair cells => otoliths, they resist motion –> bends and stimulates signals to brain –> detects linear acc vs hair cells = located in swellings of canals => ampulla, endolymph resist motion when head rotates –> bends underlying hair cells –> detects rotational acc

Question 11

Absolute vs recognition vs differential vs terminal threshold

Answer 11

Lowest decibel a human can hear vs how much decibels it take to recognize a sound source vs how much decibels to detect a difference between 2 same auditory stimuli vs highest decibel a human can hear

Question 12

How do cochlear implants work?

Answer 12

1. sound travels to microphone
2. microphones converts sound to electrical impulse on transmitter/transmitting coil
3. transmitter/transmitting coil sends signal to receiver
4. receiver sends signal to stimulator in cochlea; electrode array is in cochlea too
5. cochlea converts electrical impulse to neural impulse –> auditory nerve

Question 13

Vestibule

Answer 13

space of bony labyrinth of inner ear containing the utricle and saccule

Question 14

Hair cells in cochlea = what type of receptors?

Answer 14

mechanoreceptors