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Thursday, October 14, 2004The remarkable, almost Rube Goldberg-like progression of sound through the human ear leads to a snail-like structure in the inner ear known as the cochlea. Lining the cochlea's inward spiral is a very narrow and very long ribbon of hair cells. Scientists have named these hair cells for their tufts of up to 300 microscopic cilia that sway back and forth in response to vibrations, almost like sea anemones waving in the ocean. Tiny strings linking the hairs together loosen and tense in response to the movement, Corey said, effectively opening and closing small channels. When open, the channels allow ions like potassium to rush in and create an electrical voltage, creating a signal that zips from connected neurons to the brain, which then perceives the signal as sound. But researchers couldn't pinpoint the agent of the transformation from sound vibrations to nerve impulses until the completed DNA sequences of fruit flies, mice and humans revealed candidates in a family of related ion channels. In mice and frogs, molecular probes revealed that one candidate protein localized to the tips of the hair cell's cilia, where scientists knew the mystery channel ought to be. And when the researchers blocked production of that protein, TRPA1, hair cells in both zebrafish and mice no longer responded to mechanical vibrations. posted by Sydney on 10/14/2004 07:53:00 AM 0 comments 0 Comments: |
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