09.01 Introduction

Homeostasis (Figure 9.1) is a balancing act!

Figure 9.1 Homeostasis is a balancing act (Copyright Sheila Doggrell, QUT)

Many years ago it was identified that we have an internal environment in our bodies, and that we need to preserve this to maintain life. This preservation of the internal environment is known as homeostasis (fromthe Greek words homis, meaning ‘like’, and stasis, meaning ‘standing still’). For homeostasis, many variables within the body have to be kept relatively constant. No matter what the changes are outside the body,the internal environment is maintained. If not, we die. These variables (another name for them is parameters) are things such as temperature, pH (acid-base balance), amount of energy, etc.. These variables are all important in the functions of our bodies. For example, for cells to survive they need to have specific environmental conditions. For cells to survive they need a pH around 7.35-7.45. Similarly, for all the other variables there is a small range of normal values that are needed to maintain life.