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Nervous System
Published in Joseph D. Bronzino, Donald R. Peterson, Biomedical Engineering Fundamentals, 2019
Sensory receptors are specialized cells that, in response to an incoming stimulus, generate a corresponding electrical signal, a graded receptor potential. Although the mechanisms by which the sensory receptors generate receptor potentials are not exactly known, the most plausible scenario is that an external stimulus alters the membrane permeabilities. en the neuron’s receptor potential is the change in intracellular potential relative to its resting potential.
Abnormal neural adaptation consequent to combined exposure to jet fuel and noise
Published in Journal of Toxicology and Environmental Health, Part A, 2022
Differences (e.g., head size, electrode placement and adipose disposition) between individual subjects contribute significant variability in CAP amplitude recordings. To mitigate these effects, the ratio between the summating potential (SP), a hair cell receptor potential and the CAP (also referred to as the action potential or AP) is sometimes used (e.g., SP/AP ratio). However, this approach is based upon two assumptions: 1) the hair cell receptors are present and functioning at normal capacity and 2) a large ratio is evidence of poor neural activity. With regard to the first assumption, Guthrie and Bhatt (2021) reported that depletion of hair cell receptors across regions of the basilar membrane may nonetheless produce what appears to be normal functions. Therefore, damaged receptor cells may present with a normal SP/AP ratio. The second assumption ignores the fact that the SP may change its polarity from negative to positive based upon spontaneous and stimulus-induced alterations to hair cell physiology (Davis et al. 1958). Therefore, SP/AP ratios attributed to poor neural activity might be erroneous. Further, any recorded CAP is shaped by the Euclidean features (whether pathological or not) of the internal auditory meatus and/or dura mater which indicates that SP/AP ratios may be suggestive of neural pathologies when in fact the nerve is normal (Brown and Patuzzi 2010). To circumvent these limitations and avoid assumption-based interpretations, direct measures of functional integrity of the nerve are often preferred. The within-nerve (repeated measurement of the same nerve) response to changes in stimulus speed circumvents issues of head size, electrode placement, and disposition of adipose tissue and makes no assumption regarding the integrity of the receptor hair cells.