Hair Bundles As Sound Detectors and Amplifiers
Research of the past decades has shown that outer hair cells do not send neural signals to the brain, but that they mechanically amplify low-level sound that enters the cochlea. The amplification may be powered by movement of their hair bundles, or by an electrically driven motility of their cell bodies. The inner hair cells transform the sound vibrations in the fluids of the cochlea into electrical signals that are then relayed via the auditory nerve to the auditory brainstem and to the auditory cortex.
Results in recent years further indicate that mammals apparently have conserved an evolutionarily earlier type of hair-cell motility. This so-called hair-bundle motility amplifies sound in all non-mammalian land vertebrates. It is affected by the closing mechanism of the mechanical sensory ion channels at the tips of the hair bundles. Thus, the same hair-bundle mechanism that detects sound vibrations also actively "vibrates back" and thereby mechanically amplifies weak incoming sound.
Read more about this topic: Hair Cell
Famous quotes containing the words hair, bundles, sound and/or detectors:
“While my hair was still cut straight across my forehead
I played about the front gate, pulling flowers.
You came by on bamboo stilts, playing horse,
You walked about my seat, playing with blue plums.”
—Li Po (701–762)
“He bundles every forkful in its place,
And tags and numbers it for future reference,
So he can find and easily dislodge it
In the unloading. Silas does that well.
He takes it out in bunches like birds’ nests.”
—Robert Frost (1874–1963)
“I am already kindly disposed towards you. My friendship it is not in my power to give: this is a gift which no man can make, it is not in our own power: a sound and healthy friendship is the growth of time and circumstance, it will spring up and thrive like a wildflower when these favour, and when they do not, it is in vain to look for it.”
—William Wordsworth (1770–1850)
“There were metal detectors on the staff-room doors and Hernandez usually had a drawer full of push-daggers, nunchuks, stun-guns, knucks, boot-knives, and whatever else the detectors had picked up. Like Friday morning at a South Miami high school.”
—William Gibson (b. 1948)