Contains the full lesson along with a supporting toolkit, including teachers’ notes.
Salt - the good and the bad
Salt is a very important component in our diets. However, it is one of those things that we only need a certain amount
of. An excess of salt can be extremely damaging to our health. That is why safefood, the Food Safety Promotion
Board has designed a safefood public information programme to raise our level of knowledge about salt and its effects.
This lesson presents important facts about the kidneys and their function in maintaining a state of homeostasis or ‘balance’ in the body’s internal environment. It also shows how you can avoid health problems caused by too much salt in your diet.
What is homeostasis?
Homeostasis is the ability of a living organism to maintain a constant internal environment despite changes in the
external environment. It is the ability to remain stable. The human body is a society of cooperative living cells, about
1014 in fact. These cells are surrounded by a very thin layer of tissue fluid. In order to ensure that this tissue fluid
environment can meet the needs of the cell, it is necessary to keep the blood in good condition.
Which major blood characteristics influence homeostasis?
Blood concentration, volume and pressure greatly affect the continuous refreshment and renewal of tissue fluid. The
supply of ‘fuel’ and other essential raw materials to the tissue cells is determined by the blood’s nutrient composition
and concentration. The pH of the blood must be kept tightly at 7.4, as even slight changes in cellular pH have a major
affect on enzyme action. By keeping the blood’s waste concentration low the various metabolic wastes can be
removed rapidly from the tissue cells and delivered to the excretory organs for expulsion. Finally, the temperature of
37°C, must be regulated to ensure a high constant rate of enzyme action to sustain normal metabolism.