Pancreas — Insulin and Glucagon

What you do

• Name the disorder caused by insufficient insulin and list three of its symptoms.
• Say why a bite of sugar candy helps a patient who has had an overdose of insulin.
• State which cells of the Islets of Langerhans make insulin and which make glucagon.

Challenges to clear

• Step through the full rise and fall.
• Reach the stage where the liver is told to release stored sugar.
• Push blood glucose high enough to trigger a large release of insulin.

The task

Follow blood sugar up after a meal and down again during a fast.

What this lesson covers

• A meal is eaten — Digested carbohydrate is absorbed from the food canal and the blood sugar level climbs above normal.
• Beta cells release insulin — The beta cells of the Islets of Langerhans, the ductless part of the pancreas, secrete insulin, which checks the rise of sugar in the blood.
• Sugar used and stored — Insulin promotes glucose utilisation by the body cells and stimulates the deposition of the extra glucose as glycogen in the liver and muscles.
• Level back to normal — With glucose being taken up and stored, the blood sugar falls back to its normal level.
• Hours without food — During fasting the cells keep drawing on the blood, and the sugar level now falls below normal.
• Alpha cells release glucagon — The alpha cells of the Islets of Langerhans secrete glucagon, which stimulates the liver to break glycogen down into glucose, raising the blood sugar back to normal.
• When glucose is low, insulin falls away and glucagon takes over the job of raising it.
• A high glucose level makes the beta cells release much more insulin to bring it down again.

Hint

InsuLIN brings sugar IN to the cells and LOWERS blood sugar; glucaGON makes the liver let glucose GO and RAISES it. Never write that insulin converts glucose to glycogen — insulin enables the cells to absorb glucose and use it or convert it into glycogen.