In GCSE Science students will look at how organisms use nerves and hormones. This is the second of five quizzes on that topic and it looks in particular at how nerves and hormones carry messages around the body.
The nervous system enables humans to react to their surroundings and coordinate their behaviour. Receptors detect stimuli outside the body and relay messages to the central nervous system and brain for processing. Certain actions are voluntary, like walking or waving your hand, and are dealt with by the brain. Others are automatic and save the body from harm e.g. pulling your hand away from fire or your pupils closing up when a light is too bright. These are called reflexes and the messages from the sensors are processed in the central nervous system without needing the brain. Other messages are automatic too, like the ones telling the heart muscles to contract and relax. These are autonomous and continue all of the time.