Biology Revision

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Nervous system

  • The nervous system controls and co-ordinates the parts of your body so that they work together at the right time.
  • Things like breathing and blinking are controlled by it.
  • It consists of the brainand the spinal cord connected to different parts of the body by nerves.
  • The body's sense organs contain receptors.
  • Receptors detect changes in the environment called stimuli.
  • The receptors send messages along nerves to the brain and spinal cord in response to stimuli from the environment. These are called nerve impulses.
  • The Central Nervous System sends nerve impulses back along the nerves to bring about a response.
  • Effectors are muscles that bring about movement, or glands which secrete hormones.
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Reflex actions

  • Volentary actions are things you have to think about to do. They are concious controlled and have to be learned.
  • Reflex actions produce rapid involentary responses and they often protect us and animals.
  • In certain examples, the brain can override the reflex actions. For example, it can tell the motor neurone in the reflex arc not to drop the hot plate you are holding.

The reflex arc consists of;

  • Stimulus
  • Receptor
  • Sensory neurone
  • Relay neurone
  • Motor neurone
  • Effector
  • Response
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