Homeostasis

2.10 Homeostasis

2.10.1 Temperature

2.10.2 Thirst

2.10.2.1 Hypovolemic

2.10.2.2 Osmotic

2.10.3 Hunger

Most of the food we take in is used to provide us with energy. This energy is used in three activities:

1) Processing of newly ingested food.
2) Basal metabolism. Ca. 55%
3) Active behaviour. Ca 12-13% +

Max Kleiber's (1947) Basal metabolism expenditure rule:

kcal/day = 70 * weight^0.75

This rule works across species, but not within species. Food deprived animals have lower basal metabolism -- the body strives to keep its weight.

Large carbohydrates are broken into simple carbohydrates such as sugar to gives us energy; e.g., glucose. To store glucose, the liver combines excess glucose molecules (i.e., glycogen). Storing and using this energy is controlled by two protein hormones from the pancreas: glucagon and insulin.

Glucagon: Promotes breakdown of glycogen to glucose. Secreted from the alpha cells of the islets of Langerhans within the pancreas.
Insulin: Promotes conversion of glucose into glycogen. Secreted from the beta cells of the islets of Langerhans within the pancreas.

For long term storage, the body converts different sugars and other molecules into adipose tissue, i.e., fat.