Hormones and endocrine glands

Find the glands

Switch the names off, then see if you can still place every gland.

The kidneys are drawn only so you can see what the adrenal glands sit on top of.

Select a gland to see where it sits, which hormone it secretes and what that hormone controls. Ovaries are found in females and testes in males; this outline shows both so you can compare.

When nerves set a hormone off

Four steps, in order. The first three are nervous; the last is endocrine.

1. 1A stimulus is detectedReceptors detect a change (a stimulus).
2. 2Impulses go to the brainThe receptors send electrical impulses along neurones to the brain.
3. 3The brain signals a glandThe brain can send impulses to a gland.
4. 4The gland secretesThe impulses trigger the gland to secrete its hormone into the blood.+

What you need to know

• The endocrine system is made up of glands that secrete hormones into the blood.
• A hormone is a chemical made by a gland. It travels in the blood to a specific target organ.
• Hormones are transported in the blood plasma to their target organs.
• Cells of a target organ have specific receptors on their surface, and the hormone binds to them.
• Other organs' cells lack the matching receptor, so the hormone does not act on them.
• Have a goA classmate says: "A hormone is posted to its target organ like a parcel, and no other organ ever gets a look in." What carries a hormone, and what decides which organs respond?

  The blood plasma carries it; matching receptors on the cells decide who responds.

  Nothing is "addressed". The hormone is carried in the plasma, and the receptor on the receiving cell is what makes an organ a target.

• Endocrine glands include the pituitary (brain), thyroid (neck), pancreas, adrenal glands (on top of the kidneys), ovaries (females) and testes (males).
• The pituitary is the master gland: TSH from the pituitary stimulates the thyroid gland to make thyroxine.
• Have a goTrue or false: the thyroid gland secretes TSH, which tells the pituitary what to do.

  False. The pituitary secretes TSH, and TSH stimulates the thyroid.

  The instruction runs the other way: the pituitary's hormone acts on the thyroid, which is why the pituitary is the master gland.

• Thyroxine controls metabolic rate, adrenaline prepares the body for fight or flight, and insulin and glucagon regulate blood glucose concentration.
• The nervous system can trigger hormone secretion: the brain can send impulses to a gland.
• Nerves act quickly with short-lived responses. Hormones are slower to act but longer-lasting, and the two systems work together.
• Have a goAnother classmate: "Hormones are slower than nerves, so they must be the weaker system." Give one fact that shows why this is not the full picture.

  Hormone effects are longer-lasting, and the two systems work together.

  Slower to act does not mean less important: the effects last longer, and both systems work together to regulate body conditions.

The big picture

The endocrine system is a set of glands that secrete hormones into the blood. Hormones are carried in the plasma, and a hormone acts on target organs whose cells have the matching receptor. The pituitary is the master gland, and the nervous and endocrine systems work together.

⚠ Watch out

In an answer, don't write that a hormone is "sent to" or "goes straight to" an organ. Write that it is secreted into the blood, transported in the plasma, and binds to the matching receptors on the cells of the target organ.

Memory hook

Hormone = a key carried in the blood. Receptor = the lock. Only a cell with the matching lock responds. Pituitary = the head teacher giving orders to other glands.

Check yourself

Sketch a body and place all six glands. Then pick one and tell its whole story aloud: hormone, job, and why only some organs respond.