The word receptor is derived from the Latin word recipere, which means “to take in” or “to receive.” Explained very simply, a receptor could be described as a docking site of a cell, typically the cell surface. When messengers, proteins or hormones reach the receptor, they trigger a specific signal in the cell. The image of a key (messenger) and lock (receptor) is often chosen as a metaphor – only when the two fit together is a reaction triggered.
Receptor: sensory cells in the body
Each receptor responds to only one specific stimulus – like the first link in a chain of our senses, the receptor functions as a kind of biological sensor. If the stimulus is strong enough, it is redirected into an action potential, reaching the central nervous system.
A distinction is made between primary sensory cells, which generate action potentials on their own (for example, the touch receptors of the skin), and secondary sensory cells, which do not generate action potentials on their own (such as the taste receptors).
Membrane receptor and nuclear receptor
The so-called membrane receptors are found on the surface of biomembranes. In addition to transmitting signals, the receptors here perform the additional function of transporting substances into a cell. In this way, however, viruses can also enter a cell.
Independently of this, special proteins function as nuclear receptors. A nuclear receptor is the landing site for certain hormones – the receptor also receives the signal here and converts it, which affects the production of certain proteins.
Receptors are highly specialized
Because each receptor is designed to respond to only one stimulus, it takes a highly specialized system to allow us to perceive a sensory input. For example, to sense touch, the skin must be equipped with receptors for cold, heat, pressure, and pain.
Each temperature receptor constantly transmits information about body temperature to the central nervous system. In doing so, it usually cannot process temperatures below 10 degrees or above 45 degrees; this is where the pain receptors kick in.
