Unit 2 part 2 (Auditory system) Flashcards Preview

Neuroscience > Unit 2 part 2 (Auditory system) > Flashcards

Flashcards in Unit 2 part 2 (Auditory system) Deck (18):
1

Sound perception

pressure wave --> sound;
- wavelength (frequency/pitch)
- power/energy of waves (intensity/loudness)

2

Intensity - quantification

intensity sensitivity range for humans: 12 orders of magnitude
--> Intensity (I) = measured pressure/SPLo (a ratio)
measured in decibels (dB)
-- range is 0 - 120, change in 20 = x10 increase
* intensity varies depending on frequency of sound

3

3 mechanisms of frequency selection in hair cells

1. frequency separation by basilar membrane
2. morphological specializations of individual hair cells
(stereocilia near apex = longer than those near base)
3. Cochlear Amplifier: adjusts sensitivity of inner hair cell
*uses somatic motor (by outer hair cells)

4

Somatic motor (for cochlear amplifier)

cell bodies of outer hair cells change size in response to membrane potential changes;

5

frequency encoding

1. place-coding:
specific axon only carries info from one location on BM --> will carry only signals re: that frequency
2. phase-locking:
axon signals in synchrony with cycles that are multiples of the sound

6

pitch

the sensation of frequency of sound waves.
human range: 20-20,000 Hertz

7

External Ear parts

cavity open to air environment; Collects sound from environment.
1. pinna
2. External auditory meatus
3. Tympanic membrane (border to middle ear)

8

Middle Ear

Semi-closed cavity (open when Eustachian tube = open);
transfers sound energy from air to liquid.
1. Ossicles (malleus, incus and stapes)
2. round and oval windows
3. Tensor tympani and stapedius muscles
4. Eustachian tube

9

Inner Ear

completely closed cavity;
* where sound energy is converted to neural signal.
1. membranous labyrinth (sacs filled w/ fluid)
2. cochlea (for hearing and vestibular f(x))

10

Cochlea structure and function

3 scalae coiled 2.5 times; IN temporal bone, only partially rigid.
1, 2. Scala vestibuli and tympani
3. Scala media;
selectively responds to sound by frequency (in continuum along length)

11

organization of the 3 scala

(in cochlea)
- scala vestibuli and tympani both filled with perilymph; communicate w/ each other at apical end.
- scala media in middle, filled w/ endolymph,
*contains organ of corti
(vestibuli//Reissner's membr//media//basilar membrane//tympani)

12

organ of corti

sits on basilar membrane in scala media, runs length of cochlea;
w/ outer and inner hair cells --> stereocilia flush against tectorial membrane;
* stria vascularis = endothelium
O of C= where nerves for auditory sensation get signals from

13

stria vascularis

the highly vascular epithelial layer on lateral side of organ of corti;
- secretes endolymph
- regulates [K+]

14

innervation pattern of hair cells

Afferent: Outer: ~10 hair cells per axon
Inner: 1 hair cell per 10 axons
Efferent: signals from superior olivary nucleus to aud. hair cells

15

Efficiency of sound transfer in middle ear comes from:

total increase in amplitude in middle ear = 60-70%
- ossicles as levers: increase 3-5 dB
- TM much larger than oval window size (25:1) --> increase 30 dB

16

Basilar membrane

moves in response to pressure wave along cochlea,
* mechanically specialized so that BM responds to different (specific) frequencies in gradient along length
--> stiff at base: high frequencies
--> wide and flexible at apex: low frequencies

17

hair cell function

- base of hair cells gives/receives aff/eff neural signals
- stereocilia cause...
a) depolarization if displaced toward longest cilia
b) hyperpolarization if displaced toward shortest cilia
* degree of displacement matches size of signal

18

Mechanical Electrical Transduction (MET) Channels

process of de/re-polarizing Hair Cells for auditory sensation.
* endolymph = rich in K+; stereocilia cytoplasm = low in K+; perilymph = lowest in K+
1. tension from tip links opens K+ channels in stereocilia
--> HC depolarizes, AP sent down axon
2. -> open volt-dep./Ca-dep. K+ channels in hair cell
--> K+ leaves HC into perilymph => REpolarize cell (QUICK!)