The cells in our body need specific conditions to function properly, even when the environment outside changes. The human body and its organs can only function if their internal conditions are kept within the desired range. The maintenance of a constant internal environment in the body is called homeostasis.

Homeostasis maintains optimal conditions for enzymes to work and for all cell functions to take place.

Control Systems

The body’s control systems are automatic and can involve either nervous responses (the nervous system) or chemical responses (the endocrine system). Within our body, homeostasis helps to control many things, including:

  • Body temperature – Maintaining the temperature at which enzymes in the body are most effective, around 37°C
  • Water content – Prevents too much water from entering and leaving cells
  • Blood glucose concentration – Controlling the storage and release of glucose, which provides a constant supply to the cells for respiration (The release and storage of glucose is controlled by insulin)

These are all regulated by the body’s automatic control systems, which include

  • Receptors – Cells that detect stimuli (A stimulus refers to a change in the environment)
  • Coordination centres (e.g. the brain, spinal cord and pancreas) – Able to receive information from the receptors and process it
  • Effectors (such as glands or muscles) – Able to produce a response to help to bring levels within the body back to normal

Maintaining the Body Environment

The automatic control systems maintain the internal body environment through a mechanism known as negative feedback. When levels are too high or too low in the body, negative feedback helps to restore equilibrium.

For example, if blood glucose levels in the body are too low or too high, negative feedback mechanisms work to bring them back to normal.

  • Later, we will look at the role of insulin and how it is linked to glucose


When levels are too lowWhen levels are too high
The receptor detects the stimulus (low levels)The receptor detects the stimulus (high levels)
The coordination centre receives and processes the informationThe coordination centre receives and processes the information
The effector produces a response to increase the levelsThe effector produces a response to decrease the levels

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