The acoustic reflex (or stapedius reflex) is an involuntary
muscle contraction that occurs in the
middle ear of
mammals in response to high-intensity sound
stimuli.When presented with a high-intensity sound stimulus, the
stapedius and
tensor tympani muscles of the
ossicles contract. The stapedius pulls the
stapes (stirrup) of the middle ear away from the oval window of the
cochlea and the tensor tympani muscle pulls the
malleus (hammer) away from ear drum. The reflex decreases the transmission of vibrational energy to the
cochlea, where it is converted into electrical impulses to be processed by the
brain. The acoustic reflex normally occurs only at relatively high intensities; activation for quieter sounds can indicate ear dysfunction and absence of acoustic reflex can indicate neural
hearing loss.
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