Blood Glucose RegulationAQA GCSE Biology: Revision notes
Section 1
What Keeps Blood Glucose Steady?
Homeostasis keeps internal conditions constant. Blood glucose concentration is one of the three things homeostasis controls in the body, alongside body temperature and water levels. Control systems that regulate these use receptors to detect a change, a coordination centre to process it, and effectors to bring about a response. For blood glucose, the coordination centre and effector role is carried out mainly by the pancreas, which monitors blood glucose concentration directly and can act on it by releasing hormones into the blood.
Section 2
How Does the Pancreas Lower High Blood Glucose?
After eating carbohydrate-rich food, blood glucose concentration rises. The pancreas detects this and secretes the hormone insulin directly into the bloodstream.
- Insulin causes body cells to take up glucose from the blood, lowering blood glucose concentration
- In liver and muscle cells specifically, excess glucose taken up is converted into glycogen for storage
- This is an example of hormonal (endocrine) control: the pancreas is the gland, insulin is the hormone carried in the blood, and body cells (especially liver and muscle) are the target organs
Insulin lowers blood glucose — think 'IN-sulin lets glucose IN to cells'.
Section 3
How Is Low Blood Glucose Corrected? (Higher Tier)
If blood glucose concentration falls too low (e.g. after exercise or between meals), the pancreas produces a second hormone, glucagon.
- Glucagon causes glycogen stored in the liver to be converted back into glucose
- This glucose is released into the blood, raising blood glucose concentration back towards normal
- Insulin and glucagon work as a negative feedback pair: each hormone reverses the effect of the other, keeping blood glucose within a narrow range
Do not mix up insulin (lowers blood glucose) with glucagon (raises blood glucose) — they have opposite effects.
Section 4
Type 1 Diabetes
Type 1 diabetes occurs when the pancreas fails to produce sufficient insulin, usually because the immune system has destroyed the insulin-producing cells.
- Blood glucose concentration can rise to a dangerously high level after eating
- Treated with regular insulin injections, which allow body cells to remove glucose from the blood
Section 5
Type 2 Diabetes
Type 2 diabetes occurs when body cells no longer respond properly to insulin (the cells become resistant to it), so glucose is not removed from the blood efficiently.
- Obesity is a significant risk factor for developing Type 2 diabetes
- Treated with a carbohydrate-controlled diet and an exercise regime, rather than insulin injections
Type 2 diabetes is not caused by a lack of insulin production — it's the cells failing to respond to insulin that is already present.
Must Know
- Blood glucose concentration, body temperature and water levels are all controlled by homeostasis
- The pancreas lowers blood glucose by releasing insulin, which causes cells to take up glucose and liver/muscle cells to store it as glycogen
- The pancreas raises blood glucose by releasing glucagon, which converts liver glycogen back to glucose (HT)
- Insulin and glucagon act as a negative feedback pair
- Type 1 diabetes = insufficient insulin produced, treated with insulin injections
- Type 2 diabetes = cells don't respond to insulin, treated with diet and exercise
That's the notes covered.
Carry on to the next subtopic.