Chapter 5 - Chapter 5 Physiological Acoustics of the...

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Chapter 5 Physiological Acoustics of the Auditory Periphery 1. Some Basic Sensory Physiology Sensory organs are concerned with three processes: o Absorbing the energy of the stimulus o Using the energy absorbed to bring about some change in the state of the sensory cell o Initiating electrical impulses in the nerve leading from the sensory organ to the CNS Neuron —nerve fibers are part of a neuron Sensory neuron —excited by the action of the stimulus on the sensory organ; responsible for conveying sensory information to the CNS Sensory neuron can be acted on directly or via a separate cell o Receptor cell —absorbs the energy of the stimulus and excites the sensory neuron; secondary sensory system o Directly to the sensory neuron is a primary sensory system o Tertiary sensory systems have an additional neuron found between the receptor cell and the sensory neuron What is the desired output? o A train of pulses that represents the magnitude of the input signal o Output signal consists of electrical impulses that arise due to the rapid discharge, and subsequent recharging, of the excited sensory neuron —neuron is either on or off o Primary aspect of pulses if how often they occur—frequency or spike rate Spike rate increases as the stimulus intensity increases o Intensity if encoded as frequency Two regions of the spike rate function that bracket the range of stimulus intensities within which the stimulus is faithfully represented by the neural code o Stimuli of low intensities are inadequate to excite discharges in the neuron o Stimuli of high intensities can be reached where no substantial increase in spike rate is realized— saturation Physical stimulus is changed into an electrical signal Magnitude of signal follows the amplitude of the physical stimulus—mimics the stimulus waveform Transduction process required to transform the energy of the stimulus into electricity o Primary systems—signal generated in the receptor region of sensory neuron
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o Secondary or tertiary systems—signal generated in the receptor cell and is called the receptor potential Ohm’s electrical law o Current (I) —rate at which charge flows o Voltage (E) —force o The conductor has resistance (R) which limits the among of current All living cells, if their interiors are compared with surrounding environment, a negative voltage is measured o Reason o (1) all living cells contain fluid, the intracellular fluid , which is separated from the extracellular or interstitial fluid outside by virtue of the cell’s outer covering or cell membrane o (2) electrical charge is carried by ions rather than electrons—ions are atoms or molecules that are enriched with ( anions ) or depleted of a certain number of electrons ( cations ), they may take on a net negative or positive charge o Chloride, sodium, and potassium are common ion found in intracellular and extracellular fluids o Intra and extracellular fluids differ in their ionic content, cell membrane
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Chapter 5 - Chapter 5 Physiological Acoustics of the...

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