Many body processes are influenced by hormones, chemical
messengers produced by glands of the endocrine system. These glands release
their hormones into the blood. The hormones are then carried to the parts of
the body whose activities they influence. The endocrine system works closely
with the nervous system to maintain the body in a stable state
(homeostasis).
As well as helping to maintain homeostasis, hormones play roles in
metabolism (chemical processes throughout the body), reproduction, growth, and
response to stress. The production of many hormones is controlled by a feedback
system; glands are kept informed of what is happening in the body and adjust
the amount of hormone they produce appropriately.
The ovaries produce oestrogen and progesterone. They are involved in
the development of female sexual characteristics at puberty.
The testes produce testosterone, which stimulates the production of
sperm and the development of male sexual characteristics at puberty.
Two types of cell in the pancreas release hormones that control the
concentration of glucose (a simple type of sugar) in the blood. When the
glucose levels are too high, the beta cells release insulin. When glucose
levels are too low, the alpha cells release glucagon.
