D3.3 Homeostasis

Homeostasis refers to the regulation of the internal environment in multicellular organisms to maintain optimal conditions.
In plant cells, the environment includes the cell wall and its fluid.
In animal cells, the extracellular matrix (collagen, elastin, etc.) and tissue fluid fill spaces between cells.
Blood (plasma) acts as tissue fluid, fully separating cells.

Maintains stable conditions inside the body despite external changes.
Regulated variables include:
- Blood glucose concentration
- Blood osmotic concentration
- Blood pH
- Core body temperature
Ensures optimal functioning of cells and organs.

Feedback control helps regulate internal conditions by adjusting physiological processes based on outcomes.

Negative Feedback
- Restores the original level when a variable moves above or below the set point.
- Maintains stability and helps in homeostasis.
- Example: Regulation of body temperature, blood sugar levels, and osmotic balance.
Positive Feedback
- Increases the gap between the original level and the new level.
- Leads to an amplified response instead of restoring balance.
- Example: Childbirth contractions (oxytocin release) and blood clotting.
- Not commonly used in homeostasis because it promotes change rather than stability.

Essential for maintaining a stable internal environment.
Requires energy but allows organisms to survive in extreme environments.

Processes that add glucose to the blood	Processes that remove glucose from the blood
Absorption of glucose from the intestine after digestion of food	Absorption of glucose by body cells for cell respiration
Release of glucose from glycogen in the liver	Uptake of glucose by liver and storage as glycogen
Release of glucose from fat or protein by breakdown reactions	Increased demand for glucose in cells due to exercise
Release of glucose from amino acids or glycerol	Excess glucose removed as fat stores