Embedded Files
Conditions in which cells can function properly are narrow.
Even quite small fluctuations in osmotic pressure, temperature or the amount of certain chemical substances can disrupt biochemical processes and in extreme cases may kill the cells.
1.1 Internal environment of the body
Figure 1 Internal environment of the body is usually kept constant.
In mammalian tissues the cells are surrounded by tiny spaces filled with tissue fluid (also known as interstitial fluid.)
The tissue fluid provides the cells with the medium in which cells have to live.
The tissue fluid must be kept constant or at least held within narrow limits.
1.2 Formation of tissue fluid
Video Processes involved in the formation of tissue fluid. Click here.
Tissue fluid is formed from the body by the process of ultra-filtration in which small molecules and ions are separated from the larger molecules and cells.
Tissue fluid consists of blood plasma minus the proteins.
Walls of the capillaries act as a filter holding back the large plasma protein molecules together with blood cells. Water, ions, nutrients and oxygen are allowed to pass through.
Question: What causes water, ions, nutrients and oxygen to be forced out of the blood in the blood capillaries?
1.3 Factors of the internal environment that must be kept constant
1 Concentration of glucose
2 Concentration of various ions, eg sodium and potassium
3 Concentration of carbon dioxide
4 Osmotic pressure, determined by relative concentrations of water and solutes (osmoregulation)
5 Temperature (thermoregulation)
6 pH
7 Certain toxic substances (eg urea) must be got rid of completely or kept at very low concentration.
Activity One
1. During exercise, carbon dioxide production by cells increases. How does the body regulate concentration of carbon dioxide in the blood? What is the stimulus for the change?
Page updated
Google Sites
Report abuse