Sensory receptor

Structure of human sensory system

A sensory receptor, or sense organ, is the part which responds to a stimulus in the internal or external environment of an organism. It is the input to the sensory system. In response to stimuli the sensory receptor fires off a nerve fibre which goes to the central nervous system.

In order to detect changes in the environment organisms need receptors. Organisms have various receptors, ranging from simple light or touch sensitive cells to complex nervous systems.

Receptors are generally specialised for the detection of a specific type of stimulus.

• Mechanoreceptor: Respond to mechanical stress or strain such as those found in the hair cells of the cochlea.
• Thermoreceptor: Respond to temperature, either heat, cold or both. The skin of most animals contains these receptors.
• Photoreceptor: Respond to changes in light. Examples include those found in the retina.
• Chemoreceptor: Detect certain chemical stimuli in the environment, such as those found in the nose and on the tongue.
• Magnetoreceptor: Allows an organism to sense direction, altitude or location by detecting a magnetic field.