The structure and function of the nervous system

• The nervous system enables humans to react to their surroundings and coordinate their behavior
• The nervous system comprises millions of neurones and uses electrical impulses to communicate quickly
• Control systems in the body include chemical and nervous responses
• Receptors detect stimuli (changes in the environment)
• The coordination center, such as the brain, spinal cord, or pancreas, processes information from receptors
• Effectors bring about responses to restore optimum levels in the body, such as core body temperature and blood glucose levels
• Nerve cells, called neurones, carry electrical messages or impulses when stimulated
• Neurones have a long fibre (axon) insulated by a fatty sheath (myelin)
• There are three main types of neurones: sensory, motor, and relay
• Information flows from receptors to effectors in the nervous system: Stimulus → receptor → coordinator → effector → response
• Receptors detect changes in the environment and stimulate electrical impulses in response
• Sense organs contain groups of receptors that respond to specific stimuli
• Examples of sense organs and their stimuli:

  • Skin: touch, temperature, and pain
  • Tongue: chemicals (in food and drink)
  • Nose: chemicals (in the air)
  • Eye: light
  • Ear: sound and position of head
• Effectors include muscles and glands that produce specific responses to detected stimuli
• Examples of effectors:

  • Muscle contracting to move an arm
  • Muscle squeezing saliva from the salivary gland
  • Gland releasing a hormone into the blood