Sensory receptors are specialised cells that detect stimuli from the environment. They convert the stimulus into a nerve impulse that is passed to the central nervous system.

A transducer converts one form of energy into another.

In a receptor, a transducer converts the stimulus energy into a nerve impulse called the generator potential.

A Pacinian corpuscle is a mechanoreceptor that detects pressure and is found deep in the skin.

The Pacinian corpuscle has the ending of a sensory neurone wrapped in layers of connective tissue called lamellae. There is viscous gel between each layer of tissue.

A stretch-mediated sodium channel is one that changes in permeability to sodium when it changes shape, for instance, when it is stretched.

Stretch-mediated sodium channels are found in the membrane of sensory neurons within Pacinian corpuscles.

1. The lamellae deform, pressing on the sensory neurone ending
2. This stretches the neurone's membrane, causing it to change shape
3. This opens stretch-mediated sodium ion (Na⁺) channels in the membrane, increasing its permeability to Na⁺
4. Na⁺ diffuses into the neurone, depolarising it and resulting in a generator potential
5. If this signal reaches the threshold, an action potential is triggered

1. Specific to one stimulus type - Pacinian corpuscles only respond to mechanical pressure
2. Act as transducers, converting the stimulus to a nerve impulse - Pacinian corpuscles transduce mechanical energy of the stimulus into a generator potential