<unk>  or sensory<unk>  is a gradual decrease over time in the responsiveness of the sensory system to a constant stimulus. It is usually experienced as a change in the stimulus. For example, if a hand is rested on a table, the table's surface is immediately felt against the skin. Subsequently, however, the sensation of the table surface against the skin gradually diminishes until it is virtually unnoticeable. The sensory neurons that initially respond are no longer stimulated to respond; this is an example of<unk> . All sensory and neural systems have a form of<unk>  to constantly detect changes in the environment. Neural receptor cells that process and receive stimulation go through constant changes for mammals and other living organisms to sense vital changes in their environment. Some key players in several neural systems include Ca2+ions (see Calcium in biology) that send negative feedback in second messenger pathways that allow the neural receptor cells to close or open channels in response to the changes of ion flow. There are also mechanoreception systems that use calcium inflow to physically affect certain proteins and move them to close or open channels. Functionally, it is highly possible that<unk>  may enhance the limited response range of neurons to encode sensory signals with much larger dynamic ranges by shifting the range of stimulus amplitudes. Also, in<unk>  there is a sense of returning to baseline from a stimulated response. Recent work suggests that these baseline states are actually determined by long-term<unk>  to the environment. Varying rates or speed of<unk>  is an important indicator for tracking different rates of change in the environment or the organism itself. Current research shows that although<unk>  occurs at multiple stages of each sensory pathway, it is often stronger and more stimulus specific at "cortical" level rather than "subcortical stages". In short,<unk>  is thought to happen at a more central level at the cortex.
Neural adaptation
Neural facilitation
Co-stimulation
Reproductive compensation
Cortical remapping
Paraspinal inhibition
Respiratory adaptation
Tetanic contraction