Saturday, February 11, 2012

Anatomy and physiology of the basilar membrane

The animal ear is fabricated up of three areas: the outer, average and close ear. Aural the close ear sits the cochlea. The cochlea is a snail-shaped accumulation that enables complete manual via a sensorineural route, rather than through a conductive pathway.9 The cochlea is a circuitous structure, consisting of three layers of fluid. The scala vestibuli and scala media are afar by Reissner’s Film admitting the scala media and scala tympani are disconnected by the basilar membrane.9 The diagram beneath illustrates the circuitous blueprint of the compartments and their divisions:2

Cross-section through the cochlea, assuming the altered compartments (as declared above)

The basilar membrance widens as it progresses from abject to apex. Therefore, the abject (the thinnest part) has a greater acerbity than the apex.2 This agency that the amplitude of a complete beachcomber travelling through the basilar film varies as it campaign through the cochlea.9 If a beating is agitated through the cochlea, the aqueous aural the three compartments causes the basilar film to acknowledge in a wave-like manner. This beachcomber is referred to as a 'travelling wave'; this appellation agency that the basilar film does not artlessly beat as one assemblage from the abject appear the apex.

When a complete is presented to the animal ear, the time taken for the beachcomber to biking through the cochlea is alone 5 milliseconds.9

When low-frequency travelling after-effects canyon through the cochlea, the beachcomber increases in amplitude gradually, again decays about immediately. The adjustment of beating on the cochlea depends aloft the abundance of the presented stimuli. For example, lower frequencies mostly activate the apex, in allegory to college frequencies, which activate the abject of the cochlea. This aspect of the analysis of the basilar film can be illustrated in the anatomy of a place–frequency map:10

Simplified schematic of the basilar membrane, assuming the change in appropriate abundance from abject to apex

The basilar film supports the agency of Corti, which sits aural the scala media.2 The agency of Corti comprises both alien and close hair cells. There are about amid 15,000 and 16,000 of these hair beef in one ear.9 Alien hair beef accept stereocilia bulging appear the tectorial membrane, which sits aloft the agency of Corti. Stereocilia acknowledge to movement of the tectorial film if a complete causes beating through the cochlea. If this occurs, the stereocilia abstracted and a approach is formed that allows actinic processes to yield place. Eventually the arresting alcove the eighth nerve, followed by processing in the brain.9

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