Mechanoreceptors

Mechanoreceptors

Sensory receptors that provide the organism with information about such mechanical changes in the environment as movement, tension, and pressure. In higher animals receptors are actually the only means by which information of the surroundings is gained and by which reactions to environmental changes are started. See Sensation

Mechanoreceptors are excited by mechanical disturbances of their surroundings through deformation of their structure, through pressure or tension, or through a combination of these. In general, little energy is required for mechanical stimuli to cause a detectable excitation in mechanoreceptors.

From a physical point of view, mechanoreceptors are energy transducers; they convert mechanical into electrical energy, which in turn triggers the nerve impulse. Deformation leads to a sequence of events which may be summarized by the following scheme: The generator current is the earliest detectable sign of excitation. The most salient characteristic of the generator current is its graded nature; its amplitude increases continuously, without visible steps, if the stimulus strength is progressively increased. When the generator current reaches a certain critical amplitude, an all-or-nothing potential is discharged in the sense organ which may then propagate as an all-or-nothing nerve impulse along the afferent axon of the receptor. See Nervous system (invertebrate), Nervous system (vertebrate)

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Mechanoreceptors 

sensory nerve endings that receive various mechanical stimuli from the external environment or viscera.

Some mechanoreceptors, called tactile receptors and concentrated in the outer integuments of animals and man, are sensitive to touch. Baroreceptors (pressoreceptors, volumoreceptors), found in the walls of the blood vessels, the heart, and hollow smooth-muscled organs, react to distension associated with elevated blood pressure or accumulated gases in the stomach or intestine. Proprioceptors are mechanoreceptors found in the musculoarticular apparatus that react analogously to the contraction or relaxation of the skeletal muscles. The mechanoreceptors of the vestibular apparatus, called vestibuloreceptors, respond with neural impulses to acceleration, vibration, or inclination of the body or head. The specific characteristics of a stimulus are coded in the mechanoreceptors by the frequency and rhythm of their impulses.