Adrenal glands and pancreas: emergencies and blood glucose
There are two adrenal glands, one above each kidney. Each has an outer cortex and an inner medulla. The cortex makes steroid hormones in three groups. Glucocorticoids, such as cortisone, regulate the metabolism of carbohydrates. Mineralocorticoids, such as aldosterone, balance the minerals: the kidney keeps more sodium and loses extra potassium. The third group, sex hormones, is made in small amounts. When the cortex hormones are out of balance, body features can change, so a doctor must decide. The medulla makes adrenaline and noradrenaline, the hormones for emergencies such as fear, a fight, excitement and exercise. They make the liver break glycogen into glucose, the heart beat faster and harder, and blood pressure rise, and the body uses more oxygen. All this gives the muscles the energy they need. The pancreas is a mixed gland. Its juice leaves from the acini along the pancreatic duct to the duodenum, and its hormones come from groups of cells called the islets of Langerhans. Alpha cells, few in number, make glucagon, and beta cells, the majority, make insulin. Together they keep blood glucose steady at about 80 to 120 mg per 100 cm³ (the book’s range). Insulin lowers it: cells take up and use glucose, and glucose is turned into glycogen or fat and stored in the liver and muscle. Glucagon works against insulin and raises blood glucose by turning liver glycogen into glucose. When too little insulin is made, the blood glucose stays high and some glucose is lost in the urine: this is the disease diabetes mellitus. A doctor diagnoses and treats it.
| Part | Hormones | Job |
|---|---|---|
| Adrenal cortex | cortisone and other glucocorticoids | regulate carbohydrate metabolism |
| Adrenal cortex | aldosterone | balances sodium and potassium |
| Adrenal medulla | adrenaline and noradrenaline | prepare the body for an emergency |
| Pancreas, beta cells | insulin | lowers blood glucose |
| Pancreas, alpha cells | glucagon | raises blood glucose |
| Blood glucose | Cells that respond | Hormone | What happens |
|---|---|---|---|
| high, after a meal | beta cells | insulin | cells take up glucose; liver and muscle store glycogen or fat; level falls |
| low, long after a meal | alpha cells | glucagon | liver turns glycogen into glucose; level rises |
Pulse at rest and after effort, with a grown-up. Sit quietly for two minutes and count your pulse at the wrist for 30 seconds, then double the number. Then walk briskly up and down the stairs for one minute and count again. Write the two numbers, say which hormone the lesson links to emergencies and exercise, and say what else it does besides speeding the heart. Stop at once if you feel dizzy.