General information processing model, to include:: Receptors.

The idea

Receptors are the sensory structures that detect a stimulus and convert it into electrical impulses travelling along sensory neurones towards the central nervous system. In the general information processing model they form the input stage: stimulus, receptor detection, sensory transmission, central decision-making, then output via the effector. Different receptors are tuned to different stimuli, for example muscle spindles detect stretch, joint receptors detect joint position and movement, and skin receptors detect touch, pressure and temperature. A performer catching a ball relies on visual receptors detecting the ball and proprioceptors reporting arm position, so the CNS can select and execute the correct response.

What earns the marks

• Receptors detect a stimulus and convert it into a nerve impulse, forming the input stage of the general information processing model.
• Sensory neurones carry impulses from receptors to the central nervous system for interpretation and decision-making.
• Different receptors are specialised for different stimuli, such as muscle spindles for stretch and skin receptors for touch, pressure and temperature.
• Receptor information is integrated with proprioceptive feedback so the CNS can select and execute an appropriate motor response.
• Accurate receptor function underpins skilled movement; impaired or delayed detection reduces the quality and timing of the response.

Common mistakes and how to put them right

• Thinking receptors produce movement.

  Put it right: Receptors only detect stimuli and send impulses; the effector muscles produce the movement.

• Confusing receptors with effectors.

  Put it right: Receptors are at the input end of the model, whereas effectors act at the output end.

• Assuming one receptor detects all stimuli.

  Put it right: Receptors are specialised, so muscle spindles detect stretch while skin receptors detect touch and temperature.

• Believing the brain detects the stimulus directly.

  Put it right: Detection happens at the receptor, and the impulse is then transmitted to the CNS.

Exam tips

• Link each receptor to its specific stimulus and to the stage of the information processing model it serves.
• Use a sporting example, such as visual receptors tracking a ball, to show how input leads to a selected response.
• Check the direction of the pathway: stimulus, receptor, sensory neurone, CNS, motor neurone, effector.
• Avoid vague wording such as 'the body senses'; name the receptor type and the stimulus it detects.