ABSTRACT
Sensory receptors convert the stimulus to which they are sensitive to a change in membrane voltage by making the membrane more permeable to one or more ions. This process is called transduction and is different in different receptors. The stimulus-evoked change in membrane potential is called a receptor potential. In some sensory systems, for example somatosensory systems, the effect is to trigger actions potentials if the stimulus is sufficiently strong. Mechanoreceptors are classified as slowly or rapidly adapting and, separately, as being of two types, type I and II, distinguished by their location and receptive fields (RFs). Type I receptors are more directly concerned with form and texture perception than type II receptors. Warm receptors increase their discharge rate in response to increasing skin temperature, whilst cold receptors respond to falling temperature. Thermoreceptor afferents get input from three to four receptors, and have very small RFs, yet infrared radiation is very poorly localized.
