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The spiral canal of the cochlea is a section of the bony labyrinth of the inner ear that is approximately 30 mm long and makes 2 3 ⁄ 4 turns about the modiolus. The cochlear structures include: Three scalae or chambers: the vestibular duct or scala vestibuli (containing perilymph), which lies superior to the cochlear duct and abuts the oval ...
Type I neurons make up 90-95% of the neurons and innervate the inner hair cells. They have relatively large diameters, are bipolar, and are myelinated. Each type I axon innervates only a single inner hair cell, but each inner hair cell is innervated by up to 30 such nerve fibers, depending on species and location within the cochlea.
In order to understand in more detail the specific functions of the cochlear nuclei it is first necessary to understand the way sound information is represented by the fibers of the auditory nerve. Briefly, there are around 30,000 auditory nerve fibres in each of the two auditory nerves.
The cochlea, dedicated to hearing; converting sound pressure patterns from the outer ear into electrochemical impulses which are passed on to the brain via the auditory nerve. The vestibular system, dedicated to balance. The inner ear is found in all vertebrates, with substantial variations in form and function.
[5] [6] The human cochlea contains on the order of 3,500 inner hair cells and 12,000 outer hair cells at birth. [7] The outer hair cells mechanically amplify low-level sound that enters the cochlea. [8] [9] The amplification may be powered by the movement of their hair bundles, or by an electrically driven motility of their cell bodies.
The cochlear duct (a.k.a. the scala media) is an endolymph filled cavity inside the cochlea, located between the tympanic duct and the vestibular duct, separated by the basilar membrane and the vestibular membrane (Reissner's membrane) respectively. The cochlear duct houses the organ of Corti. [1]
The basilar membrane is a pseudo-resonant structure [1] that, like the strings on an instrument, varies in width and stiffness. But unlike the parallel strings of a guitar, the basilar membrane is not a discrete set of resonant structures, but a single structure with varying width, stiffness, mass, damping, and duct dimensions along its length.
The purpose of this frequency map (known as a tonotopic map) likely reflects the fact that the cochlea is arranged according to sound frequency. The auditory cortex is involved in tasks such as identifying and segregating "auditory objects" and identifying the location of a sound in space. For example, it has been shown that A1 encodes complex ...