Lecture 2 - Hearing/Equilibrium

what is the external ear called

auiricle

what is the outer curved ring of the ear called

helix

what is the fleshy ear lobe called

lobule

what is the ear canal called

external auditory meatus

what is ceruminen

ear wax

what is the ear drum called

tympanic membrane

what protective features are in the external auditory meatus

hairs, sebaceous glands, ceruminous glands

what divides external and middle ear

tympanic membrane

tympanic membrane function

vibrates at same frequency as sounds hitting it, then transmits vibrations to middle ear bones

where is oval window

medial end of middle ear, deep to stapes

what/where is the pharyngotympanic tube

inferior end of middle ear. equalizes pressure when opened by swallowing or yawning

what are the auditory ossicles

malleus, incus, stapes

T/F all auditory ossicles suspended by ligaments

true

loud sounds stimulate ____ and ____ muscles to contract to prevent damage to downstream sensory cells

tensor tympani; stapedius

what motion does anterior semicircular canal monitor

head nodding up and down (yes)

what motion does lateral semicircular canal monitor

head shakes side to side (no)

what motion does posterior semicircular canal monitor

head tilts down to shoulder

what is an ampulla

swollen area of each semicircular canal where equilibrium receptors are

what are cristae ampullaris

hair cells within ampulla

what/where is the organ of Corti

in the cochlear duct. spiral organ that produces nerve impulses in response to vibration

what two nerves fuse to form vestibulocochlear nerve

vestibular nerve and cochlear nerve

where is the saccule and what motion does it monitor

vestibule. connects with cochlear canal. vertical movement (elevator)

where is the utricle and what motion does it monitor

vestibule. connects with semicircular canals. horizontal movements (head tilts, moving walkway)

what are the maculae

equilibrium receptors located in sacs in vestibule

inner hair cells of the cochlea function

the ones primarily sending sound signals to brain

outer hair cells of the cochlea function

amplify vibrations and protect hair cells by altering stiffness of basilar membrane

tectorial membrane function

transfers fluid flow info to hair cells

basilar membrane function

supports hair cells. can vary in tension to protect hair cells

where are the short stiff fibers in the ear

proximal to oval window

where are the long flexible fibers in the ear

distal to oval window

high frequency sounds stimulate ___ fibers

long distal

low frequency sounds stimulate ___ fibers

short proximal

pathway of sound to inner ear (8)

1. outer ear

2. external acoustic meatus

3. tympanic membrane

4. malleus

5. incus

6. stapes

7. oval window

8. cochlear duct (→ organ of corti)

what is pitch

perception of different frequencies

what is quality

sound characteristics like tone

what is loudness

perception of different amplitudes

what is the hearable range of sound

20-20,000 Hz/sec

what range of sound are humans most sensitive to

1,500-4,000 Hz

what sound level is a normal conversation

50 dB

what is the pain threshold for sound

120 dB

prolonged exposure above what sound level causes hearing loss

90+ dB

pathway of sound info to brain (5)

1. hair cell

2. bipolar cell

3. medulla

4. thalamus

5. auditory cortex

where is static equilibrium monitored and what is it

vestibular apparatus. linear acceleration, position of head with respect to gravity.

what type of equilibrium helps with stationary balance

static equilibirum

where is static equilibrium monitored and what is it

semicircular canals. changes in head rotation

what is conduction deafness

issues with waves getting into ear, eardrum, etc.

what is sensorineural deafness

issues with hair cells, brain, CN VIII

how do cochlear implants work

bypass conduction problems. transmitter translates sound to code, then electrically stimulates vestibulocochlear nerve

what is nystagmus

“strange” eye movements during and immediately after rotation. CNS compensates for eyes drifting during rotation by jerking rapidly in opposite directions, but continues after rotation ends

what does nystagmus without spinning mean

problem somewhere in equilibrium pathway, can be associated with vertigo, etc.

in nystagmus, impulses from ___ linked to reflex eye movements

semicircular canals