Human endocrine system

Hormones and nerves

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A hormone is a chemical substance, produced by a gland and carried in the bloodstream, which alters the activity of specific target organs.

Hormones are often called chemical messengers. Hormones control the body and their effects are much slower than the nervous system, but they last for longer.

Birth control pills in pharmaceutical packaging.
Contraceptive pills contain hormones to reduce the chances of becoming pregnant

There are important differences between nervous system control and hormonal control.

Master gland

The pituitary gland in the brain is known as a 'master gland'. It secretes several hormones into the blood in response to the body's condition, for example blood water levels. These hormones can also act on other glands to stimulate the release of different types of hormones and bring about effects.

Different hormones

The body produces a range of different chemical hormones that travel in the bloodstream and affect a number of different organs and cells in the body.

Hormones and the glands that produce them in the human body