Mechanoreceptors are structures in the body that enable people to experience physical sensations. They feed tactile information to the brain so the brain can process it, providing information about objects in the environment people interact with, as well as vibrations in the air and other sources of physical sensation. There are a number of types of mechanoreceptors, designed to sense different kinds of tactile information, and these structures function in different ways. In disorders involving sensory sensitivity, people may have problems with their mechanoreceptors or the nerves that carry information from these structures to the brain.
Physical sensations can create a sense of pressure, distortion, vibration, or tension in the mechanoreceptors. These cells are usually designed to adapt, meaning as a sensation is experienced, the signals sent to the brain change. This prevents mechanoreceptors from repeatedly sending the same signal over and over, preventing people from being bombarded with information about constant sensations like clothing. Adaption speeds vary, depending on the type of receptor.
The fastest adapter is the Pacinian corpuscle, a type of receptor designed to sense vibrations. These structures are highly sensitized. Meissner's corpuscles and hair follicle receptors, designed to sense texture and the movement of hairs respectively, are slower adapters. They adjust to changes taking place within seconds, rather than fractions of seconds as with the Pacinian corpuscles. Finally, the slowest adapters include Ruffini cells for detecting tension and Merkel's discs for sensing pressure.
All of the mechanoreceptors provide important information about the surrounding environment. As people handle objects, their receptors adapt to offer useful feedback allowing people to do everything from controlling a pencil to gently petting an animal. Adaptation allows people to adjust the level of pressure they use when handling objects and provides a high degree of sensitivity on body parts like the hands and feet. These structures are also involved in the body's sense of balance, helping the brain find the body's place in space and the environment.
Problems with the mechanoreceptors can be associated with a number of causes. Physical damage to the receptors and the connected nerves may blunt tactile sensation or cause the nerve cells to misfire, providing the brain with inaccurate information. Certain neurological diseases can damage the nerves involved, jumbling the signal sent by the mechanoreceptors. Some individuals appear to be born with sensory sensitivity and may find certain sensations intolerable or extremely unpleasant. These individuals may have cognitive or developmental disabilities caused by changes in their brain structure.
