sound vibrations are converted into action potentials in the inner ear.
sound vibrations are converted into action potentials in the inner ear.
where are sound vibrations converted into action potentials?
the inner ear
since casa serves to model functionality parts of the auditory system, it is necessary to view parts of the biological auditory system in terms of known physical models. consisting of three areas, the outer, middle and inner ear, the auditory periphery acts as a complex transducer that converts sound vibrations into action potentials in the auditory nerve. the outer ear consists of the external ear, ear canal and the ear drum. the outer ear, like an acoustic funnel, helps locating the sound source. the ear canal acts as a resonant tube (like an organ pipe) to amplify frequencies between 2–5.5 khz with a maximum amplification of about 11 db occurring around 4 khz. as the organ of hearing, the cochlea consists of two membranes, reissner’s and the basilar membrane. the basilar membrane moves to audio stimuli through the specific stimulus frequency matches the resonant frequency of a particular region of the basilar membrane. the movement the basilar membrane displaces the inner hair cells in one direction, which encodes a half-wave rectified signal of action potentials in the spiral ganglion cells. the axons of these cells make up the auditory nerve, encoding the rectified stimulus. the auditory nerve responses select certain frequencies, similar to the basilar membrane. for lower frequencies, the fibers exhibit "phase locking". neurons in higher auditory pathway centers are tuned to specific stimuli features, such as periodicity, sound intensity, amplitude and frequency modulation.
computational auditory scene analysis
although action potentials are generated locally on patches of excitable membrane, the resulting currents can trigger action potentials on neighboring stretches of membrane, precipitating a domino-like propagation. in contrast to passive spread of electric potentials (electrotonic potential), action potentials are generated anew along excitable stretches of membrane and propagate without decay. myelinated sections of axons are not excitable and do not produce action potentials and the signal is propagated passively as electrotonic potential. regularly spaced unmyelinated patches, called the nodes of ranvier, generate action potentials to boost the signal. known as saltatory conduction, this type of signal propagation provides a favorable tradeoff of signal velocity and axon diameter. depolarization of axon terminals, in general, triggers the release of neurotransmitter into the synaptic cleft. in addition, backpropagating action potentials have been recorded in the dendrites of pyramidal neurons, which are ubiquitous in the neocortex. these are thought to have a role in spike-timing-dependent plasticity.
action potential