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Cutaneous mechanoreceptors with small, accurate receptive fields are found in areas needing accurate taction (e.g. the fingertips). In the fingertips and lips, innervation density of slowly adapting type I and rapidly adapting type I mechanoreceptors are greatly increased.
Mechanoreceptors that possess a large diameter and high myelination are called low-threshold mechanoreceptors. Fibers that respond only to skin movement are termed rapidly adapting mechanoreceptors (RA), while those that respond also to static indentation are termed slowly adapting mechanoreceptors (SA). [1]
Pacinian corpuscles are rapidly adapting mechanoreceptors. As phasic receptors they respond quickly but briefly to a stimulus with the response diminishing even when the stimulus is maintained. [6] They primarily respond to vibration, and deep pressure. They are especially sensitive to high-frequency vibrations.
Since they are rapidly adapting or phasic, the action potentials generated quickly decrease and eventually cease (this is the reason one stops "feeling" one's clothes). [12] If the stimulus is removed, the corpuscle regains its shape and while doing so (i.e.: while physically reforming) causes another volley of action potentials to be generated.
The responses of different type Aβ fibers to these stimuli can be subdivided based on their adaptation properties, traditionally into rapidly adapting (RA) or slowly adapting (SA) neurons. [1] Type II sensory fibers are slowly-adapting (SA), meaning that even when there is no change in touch, they keep respond to stimuli and fire action ...
Rapidly adapting receptors are also present in this system. An example of a slowly adapting receptor in use is when a person breaks his/her arm, the arm is immobilized until it is healed. He/she does not want to forget that it is broken and do something that could potentially worsen the damage in the arm.
Pulmonary stretch receptors are mechanoreceptors found in the lungs. When the lung expands, the receptors initiate the Hering-Breuer reflex, which reduces the respiratory rate. This signal is transmitted by vagus nerve. Increased firing from the stretch receptors also increases production of pulmonary surfactant.
The activity of campaniform sensilla may be slowly-adapting (tonic), signaling the magnitude of cuticular deformation, and/or rapidly adapting (phasic), signaling the rate of cuticular deformation. [ 1 ] [ 18 ] Based on their responses to white noise stimuli, campaniform sensilla may also be described more generally as signaling two features ...