Hormones
Hormones are chemical messengers released by glands into the blood and carried to a target organ or organs.
Compared to the nervous systemBody system that includes the brain, spinal cord and nerves., hormonesChemical messengers produced in glands and carried by the blood to specific organs in the body. are much slower and act over a longer period 鈥 sex hormones such as testosteroneMale sex hormone produced in the testes, which is responsible for puberty in boys. and oestrogenA female sex hormone produced in the ovaries, which is responsible for puberty in girls and the regulation of the menstrual cycle. act over years.
Hormones play an important role in maintaining a constant state within the internal environment of the body in response to changes both inside and out.
This is known as homeostasisThis is the body maintaining a constant internal environment for the proper functioning of cells and enzymes. and is necessary for the proper functioning of cells and enzymeProteins that act as biological catalysts, meaning they speed up reactions without being used up themselves..
Two examples of hormones in the homeostatic role:
- insulin A hormone produced in the pancreas that decreases blood glucose levels. 鈥 controlling blood glucose concentrations
- ADHAnti-diuretic hormone. A hormone produced in the brain that controls the amount of water reabsorbed by the kidneys. 鈥 controlling the water content of the body, referred to as osmoregulation