Sensory receptor

As receptor (from the Latin recipere ' recorded is received ') or a specialized sensor cell is referred to in the physiology, transferred certain chemical or physical stimuli from the environment of a body or inside in a neurally similar form ( transduced ).

Features

Receptors in this sense are sensory cells. They meet in an animal not only the sensor in the art similar function and transfer stimuli - such as light falling on the retina in the eye, - into electrical signals, which are passed on to the brain. But these signals and their changes are ever experienced in a subject with special quality. Often susceptibility to certain stimulus depends on qualities in sensory cells of specific molecular structures, which are also referred to in biochemistry as a receptor.

A sensory cell is the first member of our senses. Frequently it is designed to specific stimuli - the shape and strength of their respective adequate stimuli - and converts a stimulus above a certain threshold proportional to the stimulus intensity in a receptor potential ( generator potential ) around. In a ( assigned 1 ) afferent neuron this generator potentials are mapped and solve if they exceed the respective threshold potential, action potentials, which are forwarded to the central nervous system (CNS).

So light stimuli are converted into signals, for example, in the retina of the eye, passed on afferent neurons and transmitted through the optic nerve to the brain regions that compare these stimuli as differences in brightness. The signals for the synchronization of the circadian rhythm are forwarded to hypothalamic nuclei used; projected to areas of the visual cortex, they are interpreted for reconditioning a visual impression.

With regard to the occurrence of action potentials, a distinction is physiologically two types of sensory cells:

Furthermore, sensory cells can be distinguished by the time course of their response to a constant stimulus:

With the exception of the photoreceptors most sensory cells of vertebrates upon excitation are depolarized.

Physiologists and anatomists use different definitions of primary sensory cells: For example, the photoreceptors of the retina are physiologically secondary sensory cells, since they themselves do not generate action potential. Anatomically, however, they are primary sensory cells, since they are both nerve cells and thus represent the first afferent neuron.

Other examples of receptors are baroreceptors, osmoreceptors and thermal receptors.