Co-ordinating Response (Edexcel IGCSE Biology (Modular))

Co-ordinating a Response

• Homeostasis (maintaining controlled conditions within the body) is under involuntary (automatic) control

• This means that the brain stem (or non-conscious part of the brain) and the spinal cord are involved in maintaining homeostasis – you don’t consciously maintain your body temperature or blood glucose level

• These automatic control systems may involve nervous responses or chemical responses (e.g. via hormones)

• All control systems that carry out co-ordinated responses require the following:

  • A stimulus (a change in the environment e.g. a change in glucose levels in the blood, a change in body temperature etc.)

  • A receptor (receptor cells that detect stimuli)

  • A coordination centre (such as the brain, spinal cord and pancreas), which receives and processes information from receptors

  • An effector (a muscle or gland), which brings about responses to restore optimum levels

A co-ordinated response (such as that required when there is not enough water in the blood) requires a stimulus, a receptor and an effector