Audition Flashcards
1
Q
Wavelength
A
- distance from start of one cycle to another (meters/cycle)
- Wavelength = c/ frequency (C= speed in medium)
2
Q
Frequency
A
- # cycle per second or hertz (1/period); determines pitch we hear
- 20-20,000 Hz range in humans
3
Q
Amplitude
A
- proportional to amount of pressure; conveys loudness
- Sound Pressure Level = 20 log (P/Pref) in decibels
4
Q
Outer Ear (structures & function)
A
- Outer - pinna/auricle, concha, external meatus, tympanic membrane
- Goal = funnel sound
- Band pass filter - certain frequency bands better than others
- Resonance chamber - summation of sound waves for gain/amplification
- Help w/ localization of sound b/c amount of shadowing by head and pinna tells about source
5
Q
Middle Ear (structures & function)
A
- air filled space w/ ossicles
- Malleus - incus - stapes which inserts onto oval window
- Vibrate to inc sound pressure
- Movement controlled by tensor tympani & stapedius which contract to stiffen bones and dec their enhancing effect (protective)
6
Q
Inner Ear (structures & function)
A
- cochlea; fluid-filled chamber w/in temporal bone
- Coil of 3 tubes (scala vestibuli, scala media, scala tympani)
- Vestibuli & tympani are connected and filled w/ perilymph (high Na+ low K+)
- Media contained endolymph (low Na+ high K+)
-
Organ of Corti - rest on basilar membrane; signal transduction- 1 row inner hair cells; 3 rows outer hair cells
- Vibration to oval window —> scala vestibule wave —> deflection of Corti & basilar membrane —> shearing of hair cells stereo cilia
7
Q
How is the cochlear duct organized?
A
- High frequency peaks first - near basal end
- Low frequency peaks later - near apical end
8
Q
Type I v Type II Axons
A
- Type I - thick, myelinated; afferents mainly from inner hair cells; 1 nerve per inner hair cell but 1 hair cell can connect to multiple nerves
- Type II - thin, un-myelinated; efferents mainly to outer hair cells; multiple outer hair cells innervated by 1 efferent
- Cell bodies from superior olive —> release acetylcholine —> hyper polarization of outer hair cells —> dec cochlear sensitivity & cochlear amp
9
Q
Central Auditory Path (CN 8 on)
A
- CN 8 —> bifurcates —> ipsilateral dorsal and ventral cochlear nuclei (brainstem) —> MSO & LSO (superior olivary complex) —> lateral lemniscus —> inferior colliculus (processing)—> medial geniculate nucleus —> auditory cortex
- Cochlear nuclei are mono-aural (one ear) then all else integrate both ears
10
Q
Central Auditory Organization
A
- Ea 8th nerve axon has characteristic frequency —> tonotopic mapping in 8th nerve
- Firing rate tells about amplitude or loudness (greater rate = greater amp)
- Primary auditory cortex is organized tonotopically - columnar organization w/ ea column havig characteristic frequency
11
Q
How is sound localized?
A
- MSO - medial superior olivary nucleus - interaural time differences
- Excitation from both ipsilateral & contralateral ear - LSO - lateral superior olivary nucleus - interaural intensity differences
- Excitation from ipsilateral ear; inhibition from contralateral ear (glycine)
- Contralateral delay overcome by highly efficient Calyces of Held
12
Q
Conductive Hearing Loss
A
- Sound fails to reach inner ear
- Negative Rinne (bone»_space; air conductance)
- Usually mono-aural
- Causes - OM (ossicles affected by scar tissue), otosclerosis (proliferation of ossicles)
13
Q
Sensorineural Hearing Loss
A
- Sound fails due to loss of hair cells or 8th nerve fibers
- Positive Rinne (air still»_space; bone conductance but both low)
- Usually mono-aural
- Causes - ototoxic agents, infection, acoustic trauma, aging
14
Q
Central Hearing Loss
A
- Usually bi-aural b/c loss of central pathways (unless loss of cochlear nuclei)
- Causes - tumor, stroke
15
Q
Tinnitus
A
- objective or subjective (only heard by pt)
- May be due to acoustic trauma or meds
- Tx - hearing aids, cochlear implants, cognitive therapy, Xanax, anti-dep, anti-convulsants, anti-histamines, lidocaine
