Human Nervous system

• What is the function of the nervous system?

  The nervous system allows the body to react to its surroundings and coordinate an

  appropriate response
• How does a stimulus lead to a response being carried out by the body?

  • Stimulus is converted into an electrical impulse by the receptors.
  • The electrical impulse passes along sensory neurones to the central nervous system (CNS).
  • The CNS coordinates an appropriate response and an electrical impulse is sent along motor neurones to the effector, which carries out the response.
• What sequence of events describes how the nervous system works?

  Stimulus → receptor → sensory → CNS → motor → effector → response
• What is a reflex action?

  A reflex action is an automatic and rapid response which does not involve any conscious input from the brain
• Why are reflex actions important?

  Reflex actions aid survival by preventing harm to the body.
• Describe how a reflex action occurs via a reflex arc

  • The stimulus is detected by a receptor.
  • An electrical impulse passes along a sensory neurone to the spinal cord (part of the CNS).
  • At a synapse between a sensory neurone and a relay neurone, a chemical diffuses across the gap and stimulates a new impulse which passes along the relay neurone.
  • The same process occurs at a synapse between a relay neurone and a motor neurone.
  • At the effector, an appropriate response is carried out
• What is the difference between a reflex pathway and a conscious pathway?

  Within a reflex pathway, the coordination centre is a relay neurone found in the spinal cord/unconscious parts of the brain. In a conscious pathway, the coordination centre is in the conscious part of the brain.
• What is the function of the cerebral cortex? (TRIPLE)

  controls consciousness, intelligence, memory and language.
• What is the function of the cerebellum?(TRIPLE)

  controls muscular coordination
• The brain (TRIPLE)


  What is A - cerebellum

  What is B - medulla

  What is C - cerebral cortex

  
• What is the function of the medulla? (TRIPLE)


  controls unconscious activities eg. breathing, heart rate
• Why is the investigation and treatment of the brain difficult? (HIGHER AND TRIPLE)

  • The brain is a complex and delicate organ.
  • The brain is easily damaged and destroyed.
  • Certain membranes prevent drugs from reaching the brain.
  • The exact function of each part of the brain is not known.
• What methods are used by scientists to determine brain function? (HIGHER AND TRIPLE)

  • Studying patients with brain damage
  • Electrical stimulation of the brain
  • MRI scans
• What stimuli are the receptors of the eye sensitive to? (TRIPLE)

  Light intensity and colour
• What are the two main functions of structures found within the eye? (TRIPLE)

  • Focusing on near or distant objects - accommodation.
  • Adaptation to dim light
• Describe the structure and function of the retina (TRIPLE)

  F - The retina is a light-sensitive layer found at the back of the

  eye.

  Light stimulates the retinal cells, resulting in impulses being sent to the brain.
• The eye (TRIPLE)


  A - cornea

  B - iris

  C - ciliary muscles

  D - lens

  E - suspensory ligaments

  F - retina

  G - optic nerve

  H - sclera