Homeostasis.

• What is homeostasis?


  The regulation of the internal conditions of a cell or organism to maintain optimum conditions for function in response to internal and external changes.
• How is homeostasis used in the human body?

  1. To keep the blood glucose concentration the same.
  2. To maintain body temperature.
• What does homeostasis consist of?

  Automatic control systems which make sure internal conditions of the body are as constant as possible.
• What do receptor cells detect?


  Changes in the environment.
• What do scientists call a change to the environment?

  A stimulus.
• What do the receptor cells pass information to?

  The coordination centre.
• Examples of coordination centres.

  1. Brain.
  2. Spinal cord.
  3. Pancreas.
• What do coordination centres do?

  Receive and process information from receptor cells.
• What do coordination centres send information to?

  Effector organs.
• An effector is a muscle or a gland.
• What is the job of the effector?


  To carry out the response or action in response to a stimulus.
• The nervous system consits of two parts.
• What are the parts of the nervous system?

  1. Central nervous system.
  2. Other nerves running to and from the central nervous system.
• What are neurons?


  Nerve cells.
• effectors are usually a muscle which contracts/
• what is a key role of the nervous system?


  It enables humans to react to their surroundings.
• Reflex arc.

  1. Stimulus is detected by a receptor.
  2. Electrical impulses pass from the receptor along a sensory neuron into the central nervous system.
  3. Synapse releases a chemical which triggers an electrical impulse.
  4. The electrical impulse now passes across the relay neurone reaching another synapse and releasing another chemical.
  5. This chemical triggers an electrical impulse in a motor neurone to the effector and movement occurs.
• Sensory neurons are connected to receptors which allow us to sense our environment.
• In reflex actions there is no decision making by the conscious part of the brain making them automatic and rapid.
• What does the brain control?

  Complex behaviour such as language.
• What does the brain contain?

  Millions of interconnected neurones.
• Different parts of the brain carry out different functions.
• What is the name of the highly folded outer part of the brain?

  Cerebral cortex.
• What are the functions of the cerebral cortex?

  1. Language.
  2. Memory.
  3. Consciousness.
• What does the cerebellum control?

  1. Balance.
  2. Coordinates our movements.
• What does the medulla control?

  1. Heart rate.
  2. Breathing rate.
• It is very difficult to treat brain damage or brain diseases.
• Why is it difficult to treat the brain?

  1. Brain is protected by the skull making it hard to access.
  2. The brain has extremely complex structures.
  3. The brain is delicate and easy to damage.
• Three ways scientists use to investigate the brain.

  1. MRI scanning.
  2. Look at patients who suffered from brain damage.
  3. Electrically stimulating different parts of the brain.
• Why do scientists look at patients who have suffered from brain damage?

  To see where the damage has taken place and link it to its function.
• Why do scientists electrically stimulate different parts of the brain?

  To look at the effects on the persons behaviour allowing us to narrow down specific regions to their functions.
• Why do scientists electrically stimulate different parts of the brain?

  To look at the effects on the persons behaviour allowing us to narrow down specific regions to their functions.
• Why do scientists use MRI scanning to look at the brain?

  Allows us to see which parts of the brain are active during different activities.
• What type of organ is the eye?

  Sense organ.
• What is the function of the cornea?

  Transparent layer at the front of the eye which refracts light into the eye.
• What is the function of the iris?

  Coloured part of the eye containing muscles which control the amount of light entering the eye.
• What is the function of the pupil?

  The hole in the middle of the iris which lets light in. Its diameter is controlled by the iris.
• What is the function of the lens?

  A transparent biconvex structure in the eye which refracts light onto the retina.
• What is the function of the retina?

  Thin layer of tissue at the back of the eye containing receptor cells for light and colour.
• What is the function of the sclera?

  Tough white supporting wall of the eye.