receptorpotentialen

Receptor potentials are graded electrical responses produced by sensory receptors in response to stimuli. They are localized changes in the membrane potential at the site of transduction and are not all-or-none; their amplitude is proportional to stimulus intensity and can be depolarizing (in most mechanoreceptors or chemoreceptors) or hyperpolarizing (as seen in photoreceptors in response to light, where light closes cation channels, causing hyperpolarization). The receptor potential results from stimulus-induced opening or closing of ion channels, leading to changes in ion flux, often involving Ca2+ that modulates transmitter release.

In many sensory systems, receptor potentials occur in specialized receptor cells that synapse onto an afferent neuron. The magnitude and duration of the receptor potential influence the release of neurotransmitter onto the primary sensory neuron, which then fires action potentials; thus the receptor potential serves as a generator potential that encodes stimulus intensity and duration. In visual receptors (rods and cones), the receptor potential is hyperpolarizing with light and modulates glutamate release onto bipolar cells. In somatosensory and auditory systems, depolarizing receptor potentials increase transmitter release and can trigger action potentials in the afferent neuron when the depolarization reaches threshold, potentially via temporal or spatial summation.

Receptor potentials exhibit adaptation: the response diminishes during a sustained stimulus, varying from fast to slow adaptation. They are the first stage in transduction and are distinct from the all-or-none action potentials that carry information along the nervous system.