2.3 Nervous Coordination

2.3 Nervous Coordination
  1. A stimulus is any change which occurs outside or inside the human body that brings about a response.
  2. A receptor is a cell in the sensory organ which detects stimulus and convert the stimulus into electrical impulses.
  3. There are five main types of sensory organs, the eyes, ears, tongue, nose and skin.
  4. The reaction to a stimulus is called response.
  5. A response may be in the form of movement, caused by muscles or in the form of secretions, produced by glands.
  6. Muscles and glands which respond to stimuli are called effectors.
  7. All receptors and effectors are connected to the nervous system by neurones.


Reflex actions
  1. A reflex action is a fast, automatic and involuntary response towards a stimulus. It is carried out without conscious by the brain.
  2. Reflex actions help us to survive and to protect us from dangerous situation. For example, jerking away of hand when in contact with a hot kettle.
  3. Reflex actions take place in the spinal cord.
  4. The path of reflex action is called a reflex arc.
Flow chart showing reflex action occurring through the spinal cord

Example of reflex action when hand is pricked by a sharp nail

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