The Importance of Homeostasis
- Homeostasis is the regulation of the internal conditions of a cell or organism
- Some examples of these internal conditions include:
- Water content (of an individual cell or of the body fluids of an organism)
- Body temperature
- pH
- Blood pressure
- Blood glucose concentration
- It is important for an organism to respond to internal and external environmental changes whilst maintaining optimum internal conditions for enzyme action and healthy cell functions
- If the homeostatic limits are exceeded, the organism may die
Control of 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
- All control systems include:
- Cells called receptors, which detect stimuli (changes in the environment)
- Coordination centres (such as the brain, spinal cord and pancreas) that receive and process information from receptors
- Effectors (muscles or glands) which bring about responses which restore optimum levels
Negative Feedback
- The majority of homeostatic control mechanisms in organisms use negative feedback to maintain homeostatic balance (ie. to keep certain physiological factors, such as blood glucose concentration, within certain limits)
- Outcome of a negative feedback loop:
- The factor/stimulus is continuously monitored If there is an increase in the factor, the body responds to make the factor decrease
- If there is a decrease in the factor, the body responds to make the factor increase
- The system is restored to its original level
- Negative feedback mechanisms are usually a continuous cycle of bringing levels down and then bringing them back up so that overall, they stay within a narrow range of what is considered ‘normal’
A negative feedback control loop
