Reading...
Play button
Play button
Use LEFT and RIGHT arrow keys to navigate between flashcards;
Use UP and DOWN arrow keys to flip the card;
H to show hint;
A reads text to speech;
23 Cards in this Set
- Front
- Back
|
Inner Hair Cells
|
-primary system for sensing sound
-respond to movements of basilar membrane relative to the tectorial membrane -Deflected by endolymph |
|
|
Outer Hair Cells
|
-amplify sound by changing length
-longer = hyperpolarization -shorter = depolarization -deflected by tectorial membrane -efferent input in response to loud sounds dampens responses of outer hair cells as a protective measure. -efferent connections are from central superior olive |
|
|
Stereocilia
|
-surrounded by endolymph high in K, low in Na
-K flows into stereocilia = depolarization -Ca flows into actual cell and K exits via Ca activated K channels (Hair cell surrounded by normal EC fluid) -connected by tip links -longest one is kinocilium |
|
|
Kinocilium
|
-longest stereocilia
-stereocilia deflected towards it = more channels open -stereocilia deflected away from it = more channels closed -15% of channels open at rest |
|
|
Basilar membrane
|
-base is narrow and stiff, apex is wide and floppy
-has particular spots where certain frequencies resonates best. |
|
|
Tonotopy
|
-the ordered arrangement of frequencies along the basilar membrane.
-highest frequencies near base (near stapes) -lowest frequencies at apex -maintained through cns |
|
|
Tuning curves
|
- at hair cell's "best frequency" less pressure is needed to produce a response
-during varied frequency stimulation, hair cells respond strongly at a particular range of frequencies. -K channels in areas that respond to lower frequencies activate slowly, is relatively insensitive to Ca,and not densely expressed. (activate quickly with high frequency areas) |
|
|
Cochlear ganglion
|
-cell body resides inside cochlea (like DRG)
-travels to cochlear nuclei |
|
|
Auditory transduction
|
Hair cell deflection --> depolarization of hair cell --> synapsed on by cochlear ganglion --> through 7th cranial nerve -->processed at olivary nuclei in pons --> lateral lemniscus --> processed at inferior colliculus in midbrain--> ascends to medial geniculate nucleus (thalamus) --> primary auditory cortex
|
|
|
Cochlear nucleus (CN)
|
-receives auditory info in medulla
-sends signal contralaterally and ipsilaterally towards the inferior colliculus -mapped by frequency so brain knows what has been heard by the part of the CN active -sound encoded by anotomical position of active cells -different CN cellls respond in specific ways to input -encodes different attributes of stimulus |
|
|
Ventral CN
|
-locates sounds in horizontal axis
|
|
|
Dorsal CN
|
-locates sounds in vertical axis
|
|
|
Superior olivary nuclei (SO)
|
-one pathway from CN goes to SO
-sends efferent signle to outer hair cells to dampen the amount in which they lengthen -protects hair cells from damage by loud noises |
|
|
Lateral SO
|
-localize sound by comparing INTENSITY of sound from each ear
-ear contralateral to sound is dampened so there is inhibition -ipsilateral ear reinforced by excitation -Balance of excitation/inhibition determines how near to each ear the sound is |
|
|
Medial SO
|
-localizes sound by comparing timing between inputs at each ear.
-temporal difference known as interaural time difference (ITD) -two inputs compared by coincidence detectors in the MSO -doesn't work for high frequencies. |
|
|
Coincidence detector
|
-ipsilateral inputs arrive simultaneously
-contralateral inputs arrive in a temporal pattern -the two MSOs have to work together to localize sound -each MSO can only compare sounds from the contralateral sound hemisphere since all sounds in the ipsilateral sound hemisphere arrive at the same time on the coincidence detector regardless of position on ipsilateral side. |
|
|
Inferior colliculus
|
-located in the midbrain
-signal arrives from CN and SO -important in sound localization -specialized in night hunting animals -output is to superior colliculus |
|
|
Superior colliculus
|
-where visual and auditory maps are compared
-specific superior colliculus neurons fire best when sound input arrives from specific parts of the auditory field. -matches this field with visual field |
|
|
Medial geniculate nucleus
|
-in thalamus
-info travels through to primary auditory cortex -made of stacked layers, each responding to a certain frequency -projects this map to cortex |
|
|
Primary visual cortex
|
-has tonotopic map
-in monkey, different areas respond to specific frequencies and the map is repeated three times in parallel -consits of summation columns and suppression columns |
|
|
Summation columns
|
-neurons respond strongly to contralateral input
-ipsilateral input also excites these cells |
|
|
Suppression columns
|
-neurons respond strongly to contralateral input
-ipsilateral input suppresses these cells |
|
|
Core and belt
|
-frequency map is found in core
-belt encodes different aspects of sound -ventral stream arises from core and encodes the "what" part of sound -dorsal stream arises from belt and encodes the "where" part of sound |
