In the central chamber (Scala Media) of the cochlea lies the Organ of Corti - the location at which sound is transduced into neurological signals. The floor of this structure is called the Basilar Membrane while the ceiling is called the Tectorial Membrane . The auditory receptor cells, called Hair Cells , stand between these two membranes. When the vibrating ossicles press on the membrane called the Round Window , this sets up a vibration in the Cochlear Fluid that fills the cochlea. As that vibration moves through the cochlea, from Base to Apex and back, the Basilar Membrane moves up when the Tectorial Membrane moves down, bending the Cillia of the receptor cells in between. This deformation of the Hair Cells causes K+ to flow into those cells, which Decreases the polarity of that cell. Ultimately, this causes Ca++ to enter, and, as a result, Neurotransmitter is released, in a Graded Potential . The following are auditory-system examples of what fundamental principle?
- The brain encodes information through the distribution of activity across multiple cells.
- In Place Coding, frequency in the Cochlea is coded as the relative volume of NT released, along a length of the Basilar Membrane.
- In Temporal ("Rate") Coding, frequency in the Cochlea is coded as the rate at which pulses of NT are released, along the entire active Basilar Membrane.
- As in the Volley Principle, while no Spiral Ganglion can, on its own, reproduce a 3kHz rhythm of NT release, a group of these cells, working in concert, can.