Tiny muscles behind the eardrum contract involuntarily when a person vicalized or is exposed to a loud noise. This neuromuscular control system prevents sensory overload and enhances sound discrimination.
Modern industry has produced a noisy world. The din of Jack-Hammers, the whine of jet engines and the blare of amplified electric guitars have become all too common place. It was therefore considerate of nature to have equipped the human ear with a rather sophisticated noise-reduction system: two small muscles that are attached to the ossicles, the tiny bones that connected the eardrum to the cochlea(the structure that houses the sound-receptor cells). When the muscles contract, they dampen the vibrations of the ossicles, thereby reducing the acoustic signal that ultimately reaches the inner ear.
Although they are skeletal muscles (in facet they are the smallest skeletal muscles in the human body), the middle-ear muscles are not under voluntary control. They contract reflexively about a tenth of a second after one or both ears are exposed to loud external sounds. Indeed, the characteristics of the reflex have become so well known that deviations from the normal response serve as a basis for diagnosing various hearing disorders and neurological conditions.
我刚刚明明可以复制的，一瞬间就不行了.... muscles behind the eardrum contract involuntarily when a person vocalizes or is exposed to a lound noise. This neuromuscular control system prevents sensory overload and enhances sound discrimination.
Modern industry has produced a noisy world. The din of Jack-Hammers, the whine of jet engines and the blare of amplified electric guitars have become all too common place. It was therefore considerate of nature to have equipped the human ear with a rather sophisticated noise-reduction system: two small muscles that are attached to the ossicles, the tiny bones that connect the eardrum to the cochlea (the structure that houses the sound-receptor cells). When the muscles contract, they dampen the vibrations of the ossicles, thereby reducing the acoustic signal that ultimately reaches the inner ear. Although they are skeletal muscles (in fact they are the smallest skeletal muscles in the human body), the middle-ear muscles are not under voluntary control. They contract reflexively about a tenth of a second after one or both ears are exposed to loud external sounds. Indeed, the characteristics of the reflex have become so well known that deviations from the normal response serve as a basis for diagnosing various hearing disorders and neurological conditions. 可惜只复制到这里
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发表于 2011-12-17 05:38:55
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