Human nervous system

• Why should body temperature be kept in a narrow range?

  So enzymes work well
• Which word means a change in the environment?

  Stimulus
• Explain how the information about the sharp point touching the skin reaches the man's brain.

  Sharp point stimulates receptor sending impulse via sensory neurone to spinal cord crossing synapse to other neurones
• The control of blood sugar level is an example of an action controlled by hormones. Give two ways in which a reflex action is different from an action controlled by hormones.

  reflex action quicker

  effect of reflex action over shorter period
• The doctors found that the man could feel the sharp point when the point touched his arms but not when the point touched his legs. Suggest what this information could tell the doctors about the damage to the man's spinal cord. Explain your answer.

  Damage must be between arms and legs since information from nerves in arms still reaches the brain
• Describe the function of receptors in the skin.


  detect changes in surroundings

  convert information to impulse
• Describe the pathway taken by the nerve impulse in the blink reflex.

  from light-sensitive cell to connecting neurone to sensory neurone to brain to motor neurone to eyelid muscle
• Suggest how the fMRI scanner could help to find out more about the brain damage a person has.


  can ask people to do different tasks

  to see which part of brain is active

  to compare with a person without brain damage
• How is information passed across a synapse?

  Chemical
• Describe how the brain receives information about light entering the eye.

  retina sensitive to light

  impulse passes along neurone

  optic nerve
• Explain why a long-sighted person has difficulty seeing near objects clearly.


  eye is short

  light 'focuses' behind retina
• Long-sightedness can be corrected by wearing spectacles. Describe how spectacle lenses can correct long-sightedness.

  Convex

  light rays bent more

  light rays focused on retina