5.3.1(Roles of sensory receptord)

Describe what is meant by a transducer

• A cell which converts one form of energy into another

Describe and explain the role of a sensory receptor

• Sensory receptors are transducers

• All receptors are specific to a single stimulus

• Each stimulus is a form of energy - heat, light, sound, mechanical

• It detects a stimulus and converts it into electrical energy, a form that can be detected by the brain

• The energy from the stimulus is converted into a generator potential

• This initiates an electrical impulse that can be interpreted by our brain

Describe what a Pacinian corpuscle is

• A Pacinian corpuscle is a pressure sensor that detects changes in pressure on the skin

Describe the structure of a Pacinian corpuscle

• Oval shaped

• A single sensory neurone at the centre of layers of tissue

• Each layer is separated by a gel

• The sensory neurone ending at the centre of the corpuscle contains stretch mediated sodium channels

Describe how an action potential is generated at the Pacinian corpuscle

• When pressure is applied the layers are distorted, stretching the corpuscle

• This allows sodium ions to flow into the neurone, changing the polarity of the neurone

• This is the generator potential

• Once a threshold is met, an action potential is initiated ad an impulse passes to the brain

Describe how an impulse is created

• At rest the cell is polarised, negatively charged on the inside

• The stimulus causes the sodium channels to open, ions diffuse into the cell

• The influx causes more sodium channels to open, more ions diffuse in

• The inside of the cell becomes less negative, it is depolarised

• A small stimulus will only only a few sodium channels and may not initiate an impulse

• If the potential difference across the cell membranes changes enough, an impulse is generated