Homeostasis in Biology

Homeostasis

• Homeostasis is the maintenance of a constant internal environment in the body.
• It involves all the different collective processes that an organism carries out to maintain the internal conditions necessary for survival.
• There are three main conditions that need to be maintained:
  • Temperature - This is important for enzyme function.
  • Blood glucose concentration - This provides the cells with energy.
  • Water potential - This is essential for the transport of essential substances and for the correct functioning of cells.
• Enzymes require specific conditions to function properly.
• If internal conditions are too hot or too acidic, or too alkaline, enzymes will be denatured, meaning they stop functioning.
• Changes in the environment (stimuli) are detected by the body and responded to via homeostasis. Examples of stimuli include:
  • Temperature
  • Light
  • Sound
  • Pressure
  • Pain
  • Chemical changes
  • Changes in position.

Automatic Control Systems

• Automatic control systems are involved in maintaining a constant internal environment at the right levels.
• They involve nervous responses, regulated by the nervous system, or chemical responses, regulated by the endocrine system.
• These systems have three main components that all work together:
  • Receptors detect specific stimuli in the internal environment.
  • Coordination Centre receives and processes information from the receptors.
  • Effectors respond to the signals from the coordination centre to regulate internal conditions.

Negative Feedback Loops

• The process of restoring optimum levels is called a negative feedback loop.
• In a negative feedback loop, the response to a stimulus counteracts the original stimulus.
• For example, if the body temperature rises, the control system will initiate cooling mechanisms, such as sweating, to reduce the temperature.
• This is important for maintaining a stable internal environment.
• This process is similar to maintaining a "balance" in the body, keeping internal conditions within a narrow range. The body doesn't want an imbalance of anything, for example where internal conditions are either too hot or too cold.
• This process, for example, maintains a healthy body temperature of approximately 37 degrees Celsius.

### Example of Homeostasis

• Example of a stimulus: A burning hot pan.
• The receptors in the palm of the hand (detect pain and changes in temperature) send a signal to the coordination centre (the brain).
• The coordination centre then triggers a response (drop the pan) which is carried out by the effectors (muscles in the arm and hand).
• This helps prevent further damage to the hand.