OCR B6 brain and mind part1

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  • Created by: Edd
  • Created on: 10-06-12 14:36

An animal's response to a stimulus is coordinated by its central nervous system (CNS). A simple reflex is an involuntary response to a stimulus. Humans use reflex actions in only some of their behaviour, for example controlling the eye's pupil size.

Responding to a stimulus.

A stimulus is a change in the environment of an organism.

Animals respond to a stimulus in order to keep themselves in favourable conditions.

Examples of this include:

  • Moving to somewhere warmer if they are too cold.

  • Moving towards food if they are hungry.

  • Moving away from danger to protect themselves.

Animals that do not respond to a stimulus do not survive for long.

Receptors respond to a stimulus and send impulses along sensory neurons to the CNS.

Some receptors are found in the skin. Other receptors can form part of complex organs, such as:

  • Light receptor cells in the retina of the eye.
  • Hormone-secreting cells in a gland.
  • Muscle cells.
  • Position receptors in the inner ear.
  • Sound receptors in the ear.
  • Touch, pressure, temperature and pain receptors in skin.
  • Chemical receptors in the nose and tongue.

Simple reflexes.

Simple reflexes produce rapid involuntary responses to a stimulus. This ensures an animal responds in the way most likely to result in its survival.

Examples include:

  • Moving towards and finding food
  • Moving away and sheltering from predators
  • Moving towards and finding a mate

Simple animals use reflex actions for the majority


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