GCSE Biology (CIE)

Topic Summaries

The nervous system and homeostasis

Nerves and neurones

  • A bundle of neurones running parallel to each other forms a nerve.
  • A fatty layer called the myelin sheath acts as insulation around sensory and motor neurones, speeding up the speed of electrical transmission.
Sensory neurones carry electrical impulses from the receptor to the CNS
Relay neurones carry electrical impulses through the CNS.
Motor neurones carry electrical impulses from the CNS to an effector (muscle or gland).

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