Key learning points

1. Hormones are chemicals that are made and secreted by groups of specialised cells called glands.
2. Hormones are transported around the body in the blood plasma, and detected by receptors on cells and tissues.
3. During puberty, hormones cause maturation of the sex organs and development of secondary sexual characteristics.
4. Hormones control the menstrual cycle in adult human females, by causing ovulation and menstruation.
5. Decreases in hormone levels in older human females cause the menopause, after which the menstrual cycle stops.

Keywords

• Hormone - a chemical messenger secreted by glands and carried in the blood plasma

• Gland - a group of specialised cells that secrete hormones

• Puberty - the process of physical changes that lead to sexual maturity

• Ovulation - the process of an egg being released from an ovary

• Menstruation - the process of the uterus lining breaking down

Common misconception