The human body - Staying alive

Cells carry out chemical reactions that are essential for organism survival. The substance needed for the reactions have to get into cells and waste products removed from the cells.

Survival of an organism depends on its ability to respond to changes in the environment. The nervous system allows fast acting but short lived responses.

Organisms can only function if their internal conditions are kept within a specific range. This is called homeostasis. The endocrine system secretes hormones for homeostasis to occur.

Hormones are vital to enable sexual reproduction in humans. There are a range of hormones that interact to cause puberty in males and females and prepare a women’s reproductive system for pregnancy.

The control systems that keep our bodies functioning are very complicated. Sometimes they do not work as efficiently, which can lead to illness.