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Cutaneous mechanoreceptors can also be separated into categories based on their rates of adaptation. When a mechanoreceptor receives a stimulus, it begins to fire impulses or action potentials at an elevated frequency (the stronger the stimulus, the higher the frequency).
Polyphagia or hyperphagia is an abnormally strong, incessant sensation of hunger or desire to eat often leading to overeating. [1] In contrast to an increase in appetite following exercise, polyphagia does not subside after eating and often leads to rapid intake of excessive quantities of food.
Aδ fibers are characterized by thin axons and thin myelin sheaths, and are either D-hair receptors or nociceptive neurons. Aδ fibers conduct at a rate of up to 25 m/s. D-hair receptors have large receptive fields and very low mechanical thresholds, and have been shown to be the most sensitive of known cutaneous mechanoreceptors.
Examples of mechanoreceptors include baroreceptors which detect changes in blood pressure, Merkel's discs which can detect sustained touch and pressure, and hair cells which detect sound stimuli. Homeostatic imbalances that can serve as internal stimuli include nutrient and ion levels in the blood, oxygen levels, and water levels.
The plexus includes sensory receptors, such as chemoreceptors and mechanoreceptors, that are used to provide sensory input to the interneurons in the enteric nervous system. The plexus is the parasympathetic nucleus of origin for the vagus nerve and communicates with the medulla oblongata through both the anterior and posterior vagal nerves.
Stretch receptors are mechanoreceptors responsive to distention of various organs and muscles, and are neurologically linked to the medulla in the brain stem via afferent nerve fibers. Examples include stretch receptors in the arm and leg muscles and tendons, in the heart, in the colon wall, and in the lungs.
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.
Sound – When the adequate stimulus of a sensory receptor is sound, the sensory receptors are hair cells (mechanoreceptors). These hair cells contain stereocilia, which when bent, trigger the opening of ion channels. Thus hair cells transform the pressure waves of the sound into receptor potentials to initiate sensory transduction. [1]