Scientists describe your ears' natural earplugs
New research demonstrates how the sensitive cells of the ear can protect themselves from excessively loud sounds
During a typical Metallica concert, your ears take in about 100 decibels of sound - more if you forget your earplugs. The American Speech-Language-Hearing Association labels sounds louder than 80 decibels - that's about three times the sound intensity you might hear during a typical night on the library's M level - "potentially hazardous."
With so many opportunities for hearing damage, how do your ears know to "turn down" incoming sound to prevent acoustic trauma?
Now we have a better answer to this question, thanks to Hopkins researchers who genetically modified mice to create more effective sound-limiting auditory hair cells, which detect sound in the ear.
The mice were engineered with a single mutation in the receptors for acetylcholine (ACh), an important neurotransmitter which is found in hair cells.
This change in the acetylcholine receptors affected a "feedback" part of the auditory system that modulates sound signals between the brain and the inner ear.
The researchers found that the mice were significantly more protected from auditory damage than mice with normal ACh receptors.
"This point mutation was designed to produce a so-called gain of function in which the inhibitory effect of acetylcholine should be greater than normal," senior author of the paper Paul Fuchs said in a statement last week.
The team's finding is good news for patients with hearing loss and tinnitus, or persistent ringing. "We think this pathway could be a therapeutic target for protecting from sound damage," Fuchs said.
All of your sensory systems function similarly - your visual, olfactory and somatic or touch systems have specialized cells that turn sensory information (the sight of a friend, the taste of a hamburger) into electric signals that all neurons can use.
The auditory system is unique, however; though it does have specialized hair cells that sense sound, creating a signal that ultimately gets to the brain, it also modulates sound input through neurons that send signals "backwards" - from the brain to the inner ear.
With so many opportunities for hearing damage, how do your ears know to "turn down" incoming sound to prevent acoustic trauma?
Now we have a better answer to this question, thanks to Hopkins researchers who genetically modified mice to create more effective sound-limiting auditory hair cells, which detect sound in the ear.
The mice were engineered with a single mutation in the receptors for acetylcholine (ACh), an important neurotransmitter which is found in hair cells.
This change in the acetylcholine receptors affected a "feedback" part of the auditory system that modulates sound signals between the brain and the inner ear.
The researchers found that the mice were significantly more protected from auditory damage than mice with normal ACh receptors.
"This point mutation was designed to produce a so-called gain of function in which the inhibitory effect of acetylcholine should be greater than normal," senior author of the paper Paul Fuchs said in a statement last week.
The team's finding is good news for patients with hearing loss and tinnitus, or persistent ringing. "We think this pathway could be a therapeutic target for protecting from sound damage," Fuchs said.
All of your sensory systems function similarly - your visual, olfactory and somatic or touch systems have specialized cells that turn sensory information (the sight of a friend, the taste of a hamburger) into electric signals that all neurons can use.
The auditory system is unique, however; though it does have specialized hair cells that sense sound, creating a signal that ultimately gets to the brain, it also modulates sound input through neurons that send signals "backwards" - from the brain to the inner ear.
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