Principles of Homeostasis

What is homeostasis?

The maintenance of a constant internal environment via physiological control systems, keeping conditions such as temperature, blood pH, blood glucose concentration and water potential within narrow limits.

Why is it important to maintain a stable body temperature?

Enzymes control metabolic reactions and have an optimum temperature. If temperature is too low, molecules have insufficient kinetic energy and reactions slow down. If temperature is too high, bonds within the enzyme break, altering the shape of the active site — the enzyme denatures and can no longer form enzyme-substrate complexes.

Why must blood pH be kept within narrow limits?

Enzymes are also sensitive to pH. Excess H⁺ or OH⁻ ions break the hydrogen and ionic bonds maintaining the enzyme's tertiary structure, changing the shape of the active site and ultimately causing denaturation.

Why must blood glucose be regulated?

Glucose is the substrate for respiration, so cells need a constant supply. Too little and cells cannot respire and may die. Too much lowers the water potential of the blood, causing water to leave surrounding cells by osmosis, disrupting normal cell function.

What are the three components of a homeostatic control system?

A receptor (detects the change/stimulus), a coordination centre (processes the information and determines the response), and an effector (carries out the response to correct the change).

What is negative feedback and why is it important in homeostasis?

Negative feedback is when a change away from the set point is detected and a response is triggered that reverses that change, returning conditions back to the optimum. It is the key mechanism by which homeostasis maintains stable conditions.

What is positive feedback and how does it differ from negative feedback?

In positive feedback, a change is detected and the response amplifies that change further rather than reversing it. It does not maintain stability — examples include the cascade of nerve impulse depolarisation and oxytocin release during childbirth.