Sound (Audition) Flashcards
For us to hear sound we need two things (for audition to occur)
- pressurized sound wave (a stimuli)
- hair cell (a receptor, located in the cochlea)
sound waves
Air molecules are pressurized and try to escape, creating areas of high and low pressure
What are wavelength? short and higher
Wavelength: how close peaks are.
§ Smaller wavelength = greater frequency.
§ Higher wavelength (smaller frequency) = travel farther = penetrate
deeper into the cochlea.
Sound (auditory waves) path:
- First hit the outer part of the ear, known as the pinna.
- Then the sound gets funneled from the pinna to the auditory canal (also known as
external auditory meatus). - Then from the auditory canal they hit the tympanic membrane (also called the
eardrum). - As a pressurized wave hits the eardrum, it vibrates back and forth, causing 3 bones to
vibrate in this order: Malleus (hammer), incus (anvil), and Stapes (stirrups). *smallest bones, aka ossicles, acronym MIS - Stapes are attached to an oval window (aka elliptical window). The oval window then vibrates back and forth.
- As it gets vibrated, it pushes fluid and causes it to go in/around cochlea (a round structure lined with hair cells).
- At tip of cochlea (inner most part of circle), where can the fluid now go? It can only go back, but goes back to the round window (circular window) and pushes it out.
- The reason doesn’t go back to oval window, is because in middle of cochlea is a membrane – the organ of Corti (includes the basilar membrane and the tectorial membrane)
- As hair cells (cilia) move back and forth in the cochlea – an electric impulse is transported by the auditory nerve to the brain.
- The above process of fluid going around the cochlea keeps occurring till the energy of the sound wave dissipates and stops moving. Occurs more = more hair cells vibrate.
Place theory
our perception of sound depends on where each component frequently produces vibration along the basilar membrane.
one is able to hear different pitches because different sound waves trigger activity at different places along the cochlea basilar membrane
External/Outer ear:
from pinna to tympanic membrane
Middle ear
From malleus to stapes (three ossicles)
i. malleus (hammer)
ii. incus (anvil)
iii. stapes (stirrup)
Inner ear:
Cochlea and semicircular canals
Stapes – moving back and forth at same frequency as?
stimulus.
It pushes the elliptical window back and forth.
Organ of Corti splits cochlea into 2
the upper and lower
membrane.
At the upper membrane: The hair cells/cilia are called
hair bundle
hair bundles are made up of?
little filaments. Each filament is called a kinocilium
Tip of each kinocilium is connected by?
tip link which is attached to gate of K+ channel.
When the tip links get pushed back and forth by endolymph movement, they stretch and allows
When the tip links get pushed back and forth by endolymph movement, they stretch and allows K+ to flow inside the cell from the endolymph
Ca2+ role in upper membrane
Ca2+ cells get activated when K+ is inside, so Ca2+ also flows into the cell, and causes an AP, which then activates a spiral ganglion cell, which then activates the auditory nerve.
