Endocrine glands: pancreas, adrenal, thymus and gonads
The pancreas makes insulin and glucagon to control blood sugar. Adrenal glands make the emergency hormone adrenaline; the thymus and gonads make thymosin and sex hormones.
Insulin vs glucagon
Together they keep blood glucose steady. After a meal of rice, insulin rises; during a long gap between meals, glucagon rises.
Adrenal glands (suprarenal glands)
| Part | Hormone | Job |
|---|---|---|
| Adrenal cortex (outer part) | Glucocorticoids, e.g. cortisol | Control the use of glucose, fats and proteins; reduce swelling |
| Adrenal cortex | Mineralocorticoids, e.g. aldosterone | Keep the balance of salt (sodium) and water |
| Adrenal medulla (inner part) | Adrenaline (epinephrine) and noradrenaline | 'Fight or flight': faster heartbeat and breathing, more blood sugar, wider pupils |
Thymus and gonads
| Gland | Where | Hormone | Job |
|---|---|---|---|
| Thymus | Chest, above the heart and behind the breastbone; large in children, smaller in adults | Thymosin | Helps T lymphocytes (white blood cells) mature, building immunity |
| Testes | In the scrotum (male) | Testosterone, from Leydig (interstitial) cells | Sperm production; male features at puberty, like beard, deeper voice and bigger muscles |
| Ovaries | Lower abdomen (female) | Estrogen, from the Graafian follicles | Female features at puberty; growth of the uterus lining; the menstrual cycle |
| Ovaries | Lower abdomen (female) | Progesterone, from the corpus luteum | Prepares the uterus for pregnancy and keeps the pregnancy going |
Why is adrenaline called the emergency hormone?
When you face danger, like a snake on the path, the adrenal medulla quickly releases adrenaline. Your heart beats faster and breathing speeds up. More glucose enters the blood for energy, and the pupils widen. The body is ready to fight or run away. So adrenaline is called the emergency hormone or the 'fight or flight' hormone.
Choose whole grains, millets and pulses over sweets and sugary drinks; they raise blood sugar slowly, so the body handles it more easily. Daily play and exercise also help insulin work better.
2 marks: “Why is adrenaline called the emergency hormone?” It is released in danger and raises heartbeat, breathing and blood sugar, preparing the body to fight or run.
2 marks: “Name the hormones secreted by the islets of Langerhans.” Insulin (beta cells) and glucagon (alpha cells).
4 marks: “How do insulin and glucagon control blood sugar?” Insulin lowers it: glucose enters cells and is stored as glycogen in the liver. Glucagon raises it: glycogen is broken into glucose. Together they keep blood sugar normal; lack of insulin causes diabetes mellitus.
Insulin puts sugar IN (into cells and stores); Glucagon tells the liver to let the Glucose GO.