9/27/2023 0 Comments Auditory nerve earThe electrochemical gradient makes the positive ions flow through channels to the perilymph. The perilymph in the scala tympani has a very low concentration of positive ions. Repolarization of hair cells is done in a special manner. In this way, the mechanical sound signal is converted into an electrical nerve signal. The neurotransmitters diffuse across the narrow space between the hair cell and a nerve terminal, where they then bind to receptors and thus trigger action potentials in the nerve. This receptor potential opens voltage gated calcium channels calcium ions then enter the cell and trigger the release of neurotransmitters at the basal end of the cell. Instead, the influx of positive ions from the endolymph in the scala media depolarizes the cell, resulting in a receptor potential. Unlike many other electrically active cells, the hair cell itself does not fire an action potential. The deflection of the hair-cell stereocilia opens mechanically gated ion channels that allow any small, positively charged ions (primarily potassium and calcium) to enter the cell. Inner hair cells – from sound to nerve signal Section through the organ of Corti, showing inner and outer hair cells The inner hair cells transform the sound vibrations in the fluids of the cochlea into electrical signals that are then relayed via the auditory nerve to the auditory brainstem and to the auditory cortex. It is affected by the closing mechanism of the mechanical sensory ion channels at the tips of the hair bundles. This so-called somatic electromotility amplifies sound in all land vertebrates. The amplification may be powered by the movement of their hair bundles, or by an electrically driven motility of their cell bodies. The outer hair cells mechanically amplify low-level sound that enters the cochlea. The human cochlea contains on the order of 3,500 inner hair cells and 12,000 outer hair cells at birth. However, other organisms, such as the frequently studied zebrafish, and birds have hair cells that can regenerate. Damage to hair cells can cause damage to the vestibular system and therefore causing difficulties in balancing. Damage to these hair cells results in decreased hearing sensitivity, and because the inner ear hair cells cannot regenerate, this damage is permanent. Mammalian cochlear hair cells are of two anatomically and functionally distinct types, known as outer, and inner hair cells. The hair bundles are arranged as stiff columns that move at their base in response to stimuli applied to the tips. The stereocilia number from fifty to a hundred in each cell while being tightly packed together and decrease in size the further away they are located from the kinocilium. They derive their name from the tufts of stereocilia called hair bundles that protrude from the apical surface of the cell into the fluid-filled cochlear duct. In mammals, the auditory hair cells are located within the spiral organ of Corti on the thin basilar membrane in the cochlea of the inner ear. Through mechanotransduction, hair cells detect movement in their environment. Hair cells are the sensory receptors of both the auditory system and the vestibular system in the ears of all vertebrates, and in the lateral line organ of fishes. How sounds make their way from the source to your brain
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