Basrefleks

Basrefleks, also known as the acoustic reflex or stapedius reflex, is an involuntary contraction of the stapedius muscle in the middle ear. This contraction is triggered by loud sounds. The stapedius muscle is attached to the stapes, one of the ossicles in the middle ear. When the reflex is activated, the stapedius muscle pulls the stapes away from the oval window, thereby reducing the transmission of sound vibrations to the inner ear. This action serves as a protective mechanism, dampening potentially damaging loud noises and preventing injury to the delicate structures of the cochlea.

The activation of the basrefleks is typically mediated by the auditory nerve. When sound levels reach a certain threshold, usually around 70-90 decibels above normal hearing thresholds, a signal is sent to the brainstem. In response, efferent pathways from the brainstem activate the stapedius muscle. The reflex can be elicited by presenting a loud sound to one ear, which typically causes a contraction in both the ipsilateral (same ear) and contralateral (opposite ear) stapedius muscles. The latency of the reflex is relatively short, occurring within milliseconds of the sound stimulus.

The presence and characteristics of the basrefleks are often assessed during audiological examinations, such as tympanometry. Measuring the acoustic reflex threshold and its reflex decay can provide valuable information about the integrity of the auditory pathway, including the middle ear, the facial nerve, and the auditory brainstem. Abnormalities in the acoustic reflex can indicate conductive hearing loss, sensorineural hearing loss, or neurological disorders affecting the auditory pathway.