Describe where hormones are produced and how they are transported from…

The idea

Hormones are chemical messengers made in endocrine glands and released into the blood. The blood carries them around the body, but each hormone affects only its target organs, which have cells with receptors that recognise it. You need to know the site and a role for each named gland: the pituitary gland in the brain controls other glands; the thyroid gland in the neck releases thyroxine, which regulates metabolic rate; the pancreas releases insulin and glucagon to control blood glucose; the adrenal glands sit above the kidneys and release adrenalin; the ovaries release oestrogen and progesterone; the testes release testosterone. A useful method is to link each gland to its hormone and target, for example the pancreas releases insulin, which travels in the blood to the liver and muscles.

What earns the marks

• Hormones are produced by endocrine glands and secreted directly into the bloodstream.
• Transport is by the blood, which carries the hormone to target organs bearing matching receptors.
• The pituitary gland is in the brain and controls other endocrine glands.
• The thyroid gland releases thyroxine, which regulates metabolic rate.
• The pancreas releases insulin and glucagon, which act on the liver and other tissues to control blood glucose.
• The adrenal glands release adrenalin, preparing the body for fight or flight.
• The ovaries release oestrogen and progesterone; the testes release testosterone.
• Only target organs respond because their cells have specific receptors for that hormone.

Common mistakes and how to put them right

• Thinking hormones travel along nerves.

  Put it right by stating they are secreted into the blood and carried in the bloodstream.

• Believing a hormone affects every cell equally.

  Put it right by explaining that only target organs with matching receptors respond.

• Confusing which gland releases which hormone, such as naming the thyroid as the source of insulin.

  Put it right by pairing each gland with its hormone and target.

• Assuming the pituitary gland is in the abdomen.

  Put it right by placing it in the brain.

Exam tips

• Learn a three-column table of gland, hormone and target organ so you can match them quickly in multiple-choice questions.
• Read each option fully; distractors often swap the gland and the hormone.
• When an option says a hormone acts on all cells, treat it as wrong because only target organs respond.