Receptors

Receptors

An animals internal and external enviroments are continually changing. A dectectable change is called a stimulus. To some extent all cells are sensitive to stimuli, but in animals certain cells have to become especially sensitive to particular stiimuli. These are called recpetor cells. they act as tranducers, converting the energy of the stimulus into the electrical energy of a nerve impulse which is transmitted along the sensory neurone to the centeral nervous system.
A pacinian corpuscle is a receptor sesnistive to change in pressure and touch. As such, it is called a mechsnoreceptor. Pacinian corpuscles occur in the skin, tendons, mucles and joints of mammals. Each corpuscle has a single sensory neurone, one end of which consists of capsule made of conentric rings of connective tissue that acts as a pressure sensitive pad. Application of pressure against the connective tissue deforms stretch-mediated sodium ion channel proteins., in the plasma membrane. This causes an influx of sodium ions into the end of the sensory neurone. The sudden influx of sodium ions reverses the potential difference across the plasma membrane. The inside becomes temporarily postively charged, a process called depolarisation. The electrical potential created by the deformation is proportional to the stimulus intensity. This graded potential is known as the generator potential.
The pacinian corpuscle, like other receptors, respons only to specific stimulus. It responds to mechanical deformation. It does not respond to other stimuli such as temperature.

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