4.5.3.2a - Blood glucose control
Blood glucose concentration changes after eating, exercise and time between meals. The pancreas monitors and controls this concentration using hormones carried in the blood. This lesson stays with the normal control mechanism: insulin lowers blood glucose, and Higher Tier students also need glucagon and the negative feedback cycle.
Pancreas and blood glucose
Glucose is a soluble sugar carried in the blood. Body cells use glucose in respiration to release energy, so blood glucose concentration must be kept within a suitable range for cell function.
Blood glucose concentration
The amount of glucose dissolved in the blood.
The pancreas is the organ that monitors and controls blood glucose concentration. In the homeostasis model, the pancreas acts as a coordination centre because it detects when blood glucose is too high or too low and releases hormones that bring about a response.
The pancreas is also a gland. A hormone is a chemical messenger released by a gland into the blood. The blood carries the hormone to target cells or organs, where it causes an effect.
Insulin when glucose is high
After a meal containing carbohydrate, digestion can increase the glucose concentration in the blood. If the blood glucose concentration becomes too high, the pancreas produces the hormone insulin.
Insulin lowers blood glucose concentration in two linked ways. First, it causes glucose to move from the blood into body cells. Second, in liver and muscle cells, excess glucose is converted into glycogen for storage. These responses remove glucose from the blood, so the blood glucose concentration falls back towards the normal range.
Insulin
A hormone produced by the pancreas when blood glucose concentration is too high; it lowers blood glucose concentration.
A strong explanation names the stimulus, the hormone, the target response and the effect on blood glucose. Avoid saying that insulin "breaks down" glucose. For this GCSE point, insulin causes glucose uptake into cells and storage as glycogen in liver and muscle cells.
Glycogen storage
Glycogen is a storage carbohydrate made from many glucose molecules joined together. It is useful because cells can store glucose in this form until the body needs it again.
Glycogen
A storage carbohydrate made from glucose, stored mainly in liver and muscle cells.
The liver and muscles are important stores in this lesson. When insulin is present after blood glucose becomes too high, liver and muscle cells convert excess glucose into glycogen. This keeps the glucose available to the body, but no longer dissolved in the blood.
For all students, the key comparison here is between glucose and glycogen. Glucose is the soluble sugar carried in the blood; glycogen is the storage carbohydrate made from glucose and stored in liver and muscle cells.
Low glucose and glucagon
The rest of this lesson adds Higher Tier content. Foundation Tier students need the insulin branch: high blood glucose, insulin release, glucose entering cells and excess glucose becoming glycogen. Higher Tier students also need the glucagon branch. If blood glucose concentration is too low, the pancreas produces the hormone glucagon.
Glucagon
A hormone produced by the pancreas when blood glucose concentration is too low; it raises blood glucose concentration.
Glucagon causes glycogen to be converted back into glucose. The glucose is then released into the blood, so the blood glucose concentration rises back towards the normal range. In this GCSE specification, the key target organ to name is the liver because liver glycogen can be converted to glucose and released into the blood.
This response is the opposite direction to the insulin response. Insulin helps store excess glucose as glycogen when blood glucose is too high. Glucagon helps convert glycogen back to glucose when blood glucose is too low.
Continue this lesson.
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