Structure and function — AQA GCSE Biology
Test yourself on Structure and function with AQA GCSE practice questions.
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Structure and function explained
The nervous system allows humans to detect changes in their surroundings and produce appropriate responses.
Read the full explanation
Receptors detect stimuli such as light, sound, touch, temperature and chemicals. Electrical impulses travel along sensory neurones to the central nervous system, which processes the information and coordinates a response. Motor neurones then carry impulses to effectors, which are muscles or glands. Muscles contract to produce movement, while glands secrete chemicals such as hormones. This coordination allows rapid reactions, including reflexes such as withdrawing a hand from a hot object, and more complex behaviours such as catching a ball. The nervous system therefore links detection of a stimulus to a coordinated response, helping the body respond to its environment and maintain control.
Your focus
- Describe how the nervous system detects and responds to stimuli.
- Explain the roles of receptors, the CNS and effectors in coordinating behaviour.
- Give examples of rapid reactions and reflex actions.
Structure and function exam tips
Marking Points
- Receptors detect stimuli in the surroundings.
- Sensory neurones carry impulses to the CNS.
- The CNS coordinates the response by processing information.
- Motor neurones carry impulses to effectors.
- Effectors are muscles, which contract, or glands, which secrete chemicals.
- Reflex actions are rapid, automatic responses that protect the body.
Examiner Tips
- 💡Use the stimulus–receptor–coordinator–effector–response sequence in your answers.
- 💡Give a named example, such as withdrawing a hand from a hot object, to show coordination.
- 💡State clearly that the CNS coordinates the response rather than simply passing it on.
Common Mistakes
- Saying the brain directly detects stimuli; correction: receptors detect stimuli and send impulses to the CNS.
- Thinking effectors are only muscles; correction: glands are also effectors and respond by secreting chemicals.
- Confusing a reflex with a voluntary action; correction: reflexes are rapid and automatic, while voluntary actions involve conscious decision-making.