Homeostasis

Definition

Homeostasis is the maintenance of a stable internal environment within an organism despite changes in the external environment.

Importance of Homeostasis

• Maintains optimal conditions for enzyme activity and cellular function.
• Prevents damage due to extreme conditions.
• Supports survival and reproduction.

Regulation of Blood Glucose

• Pancreas releases insulin when blood glucose is high (promotes glucose uptake by cells, glycogen formation).
• Pancreas releases glucagon when blood glucose is low (promotes glycogen breakdown to glucose).

Temperature Regulation

• Hypothalamus detects body temperature changes.
• Excess heat: sweating, vasodilation.
• Cold: shivering, vasoconstriction.

Water and Osmoregulation

• Kidneys regulate water balance through urine concentration.
• ADH hormone controls water reabsorption in nephron.
• Skin and lungs also help in water loss control.

Feedback Mechanisms

• Negative feedback: counteracts deviation from normal (e.g., blood glucose, temperature).
• Positive feedback: amplifies changes (less common, e.g., childbirth contractions).

Practice Questions

• Define homeostasis and explain its importance. (4 marks)
• Describe how blood glucose is regulated. (5 marks)
• Explain temperature regulation in humans. (5 marks)
• How do kidneys help in water balance? (4 marks)
• Differentiate negative and positive feedback with examples. (4 marks)