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 â 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.