Looking at the principle of negative feedback, and how it controls blood/…

• Physiological Homeostasis
• Homeostasis of Organism Water Regulation
• Sugar Homeostasis
• Temperature Regulation in Animals
• Population Regulation in an Ecosystem
• Indicator Species and Endangered Species
• Ecosystem Succession

Osmoregulation

Osmoregulation is the regulation of water concentrations in the bloodstream, effectively controlling the amount of water available for cells to absorb.

The homeostatic control of water is as follows

• A change in water concentration leads to active via negative feedback control
• Osmoreceptors that are capable of detecting water concentration are situated on the hypothalamus next to the circulatory system
• The hypothalamus sends chemical messages to the pituitary gland next to it.
• The pituitary gland secretes anti-diuretic hormone (ADH), which targets the kidney responsible for maintaining water levels.
• When the hormone reaches its target tissue, it alters the tubules of the kidney to become more / less permeable to water
• If more water is required in the blood stream, high concentrations of ADH make the tubules more permeable.
• If less water is required in the blood stream, low concentrations of ADH make the tubules less permeable.
• This is illustrated by the flow chart below

Evolutionary Adaptations in Water Regulation

Some of the tutorial pages in the adaptation tutorial investigate some of the evolutionary adaptations that organisms have achieved through natural selection. This looks at

• Ways in which both animals and plants can be better adapted to cope with extreme environments (desert or wetlands).
• These changes can be behavioural, physical or anatomical, and in some way promote water regulation.
• Both plant and animal adaptations are investigated

More Homeostasis

The body also contains negative feedback control mechanisms for the control of blood sugar concentration and temperature regulation. These types of homeostasis are described on the next page.