Sound (Audition) Flashcards
What is audition?
sense of sound
What is needed for audition to occur?
1) Stimuli = pressurized sound wave
2) Receptor = hair cell located in the cochlea
what is pressurized sound wave and what does it create?
1) when air molecules becomes pressurized (when there is less space so the molecules compress, which creates a high pressure)
2) air molecules try to escape, creating areas of high and low pressure (known as sound waves)
Describe soundwaves.
1) can be close or far apart
2) have wavelengths (how high the peaks are)
Smaller wavelength equals ________.
Greater frequency
Large wavelengths equals __________.
smaller frequency (travels farther and penetrates deep into cochlea)
What is the purpose of the cochlea?
1) allows you to listen to different soundwaves at the same time (ear breaks them up)
2) able to do this because sound waves travel different lengths along the cochlea.
What happens when soundwaves travels through the ears?
1) Hit the pinna (outa ear)
2) Funneled from the pinna into the auditory canal (or external auditory meatus)
3) Sounds then hits the tympanic membane (ear drum)
4) TM begans to vibrate
5) Causes malleus, incus, and stapes (3 tiny bones) to vibrate - respectively in that order) — these bones are also referred to as the ossicles
6) Stapes is attached to elliptical window – causes this window to vibrate
6) Elliptical window is attached to cochlea (which has a bunch of fluid)
7) As the elliptical window is pushed inside and outside cochlea by the stapes - this causes fluid to be pushed in the cochlea
8) once fluid hits the tip of the cochlea, it goes backwards back to the elliptical window
9) Now, instead of going back into the elliptical window, the fluid goes into the circular window (causes circular window to get pushes out)
10) hair cells (cilia) move back and forth in the cochlea
11) This causes auditory nerve to send and electrical impulse to the brain
Keeps happening until the energy of the soundwave is dissipated and the fluid stops moving.
What prevents fluid from going in the elliptical window?
Organ of corti (basilar and tectorial membranes) - runs inside of cochlea
Outer ear
pinna to TM
Middle Ear
Malleus to Stapes
Inner Ear
semi-circle canals and cochlea
Describe the organ of corti.
1) splits cochlea into 2 - upper and lower membrane
2) Has hair cells that move back and forth as the membranes are pushes up and down
Describe the hair cells in the corti.
1) Has two parts: actual cell and hair bundle
2) Hair bundle and made of a bunch of filaments, each called kinocilium
3) Kinocilium are attached by “tip links”
4) Tip links (a spring like structure) are not directly attached to the kinocilium, but are attached to potassium channels
What happens to the tip links when the kinocilium move back and forth
1) they get stretch and open up the potassium gated channels
2) K+ begins to flow into the cell
3) Causes Ca+ channels on the cell to open up (Ca+ flows into cell)
4) K+ and Ca+ flow into the cell, stimulating and action potential
5) AP Stimulates a spiral ganglion cell, which activates the auditory nerve, which sends the impulse to the brain
The brain relies on the cochlea to do what?
Distinguishing sounds of varying frequencies. (also known as auditory processing)
Higher and lower sounds differ in what?
Frequency (i.e. bees have high frequency, base drum has a low frequency)
What is the range of frequency humans can hear?
20-20,000 hz
What is basilar tuning?
1) hair cells in the cochlea allow brain to distinguish high and low frequencies
2) hair cell that matches the frequency of the sound will be activated
3) that particular hair cell is mapped to a particular region the primary auditory cortex (in the temporal lobe)- part of the brain that receives all info from the cochlea)
4) When activated, the hair cell will send an impulse down an axon, which eventually becomes a part of the auditory nerve
5) When the auditory nerve reaches the brain, the axons will separate to reach different parts of the primary auditory cortex of the brain
6) This allows for tonotopical mapping (each hair is mapped to a specific region of the primary auditory cortex that is sensitive to that specific frequency)
7) If we did not have the primary auditory cortex, we would not be able to distinguish sounds of different frequencies
When are the hair cells at the base (start - 1600 hz) of cochlea activated?
high frequencies (low wavelength)
When are the hair cells at the apex (end - 25 hz) of cochlea activated?
low frequencies (high wavelength)
Cochlear Implants
surgical procedures to restore a degree of hearing (for individuals with sensorineural hearing loss)
What is another name for sensorineural hearing loss?
Nerve deafness
What is the major problem with people with sensorineural hearing loss?
Conduction of soundwaves from the cochlea to the brain
What are the parts of a cochlear implant and how does it work?
microphone, speech processor, transmitter, receiver, and stimulator
1) Sounds enters microphone
2) Info goes to speech processor
3) Then to transmitter (outside of skull)
4) Then receiver (inside of the skull) which extends to the stimulator
5) Lastly Stimulator extends into the cochlea, which converts electrical impulses to neural impulses (which shoots down into the auditory nerve and into the brain to process the sound heard)
