Do outer hair cells have innervation?
Nerve fiber innervation is much denser for inner hair cells than for outer hair cells. A single inner hair cell is innervated by numerous nerve fibers, whereas a single nerve fiber innervates many outer hair cells. Efferent synapses occur on outer hair cells and on afferent axons under inner hair cells.
What neurotransmitter do outer hair cells release?
acetylcholine
The dominant efferent innervation of the cochlea terminates on outer hair cells (OHCs), with acetylcholine (ACh) being its principal neurotransmitter.
What stimulates outer hair cells?
Information about the acoustic environment is conveyed to the auditory nerve fibers almost exclusively via the electrical signals of inner hair cells (IHCs), whereas the main task of outer hair cells (OHCs) is to boost the stimulus by mechanically amplifying the sound-driven vibrations of the cochlear partition.
Are outer hair cells efferent?
The inner hair cells are the actual sensory receptors, and 95% of the fibers of the auditory nerve that project to the brain arise from this subpopulation. The terminations on the outer hair cells are almost all from efferent axons that arise from cells in the brain.
Are there hair cells in the semicircular canals?
Each of the three semicircular canals has at its base a bulbous expansion called the ampulla (Figure 14.7), which houses the sensory epithelium, or crista, that contains the hair cells.
What do hair cells transduce?
Hair cells can convert the displacement of the stereociliary bundle into an electrical potential in as little as 10 microseconds; indeed, such speed is required to faithfully transduce high-frequency signals and enable the accurate localization of the source of the sound.
What is outer hair cells stereocilia?
Hair cell stereocilia are at the core of electro-mechanical transduction; the transformation of sound vibration into a neural signal that can be interpreted by the brain. Both types of hair cell have a similar transduction mechanism. The deflection of the stereocilia causes stretch-sensitive ion channels to open.
What happens to outer hair cell stereocilia when the basilar membrane moves upward?
As the basilar membrane moves upward, the cilia move in the direction causing opening of the mechanically gated potassium channel. The influx of potassium ions leads to depolarization.
What gives rise to Tonotopy?
In physiology, tonotopy (from Greek tono = frequency and topos = place) is the spatial arrangement of where sounds of different frequency are processed in the brain. Nerves that transmit information from different regions of the basilar membrane therefore encode frequency tonotopically.
What is the difference between outer and inner hair cells?
The main difference between inner and outer hair cells is that the inner hair cells convert sound vibrations from the fluid in the cochlea into electrical signals that are then transmitted via the auditory nerve to the brain whereas the outer hair cells amplify low-level sounds that enter into the fluids of the cochlea …
How are hair cells arranged in the semicircular canals?
The hair cells are arranged as a single tuft that projects up into a gelatinous mass, the cupula. Together, these form the crista. When the head rotates in the plane of the canal, the inertia of the endolymph causes it to wash over the cupula, deflecting the hair cells.
