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Subject: gate-control system med. Выражение: gate-control systemCNS factors can modulate our perception of itch by either amplifying or inhibiting the sensation. An example of inhibition is the effect of scratching an itch. Scratching demonstrates the concept of gating of sensory afferent activity. In this system, simultaneous firing of large-diameter myelinated fibers can presynaptically inhibit firing of smaller afferent fibers so that the sensations they usually evoke would be diminished in intensity or not perceived. Scratching stimulates firing of large-diameter myelinated A fibers that can presynaptically inhibit the firing of smaller afferent C fibers carrying itch. Psychologic factors, such as emotion and past experience, may also act on the gate-control system and modify the perception of itch. An additional central influence on itch involves the enkephalins and opioid receptors in the CNS. Заранее спасибо
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