In physiology, transduction is the conversion of a stimulus from one form to another.
Transduction in the nervous system typically refers to synaptic events wherein an electrical signal, known as an action potential, is converted into a chemical one via the release of neurotransmitters. Conversely, in sensory transduction a chemical or physical stimulus is transduced by sensory receptors into an electrical signal.
For example, in the visual system, sensory cells called rod and cone cells in the retina convert the physical energy of light signals into electrical impulses that travel to the brain. The light causes a conformational change in a protein called rhodopsin. This conformational change sets in motion a series of molecular events that result in a reduction of the electrochemical gradient of the photoreceptor. The decrease in the electrochemical gradient causes a reduction in the electrical signals going to the brain. Thus, in this example, more light hitting the photoreceptor results in the transduction of a signal into fewer electrical impulses.