Lesson 6 of 7 / Nutrition in humans
Blood glucose control
How are a glucose rise and a glucose fall corrected?
I can outline how insulin and glucagon regulate blood glucose concentration.
I can outline insulin and glucagon control.Syllabus
Syllabus K327 / K328, Topic 4(f). Outline insulin and glucagon control.
About 6 min
Make a guess. You are not marked.
You skip lunch and your blood glucose falls. Which hormone is released to raise it?
Show the answer
Glucagon, which makes the liver release glucose.
Glucagon promotes breakdown of liver glycogen into glucose, which enters the blood.
The key idea
Insulin lowers blood glucose by promoting uptake and storage; glucagon raises it by promoting glucose release from the liver.
Explore the idea
Which response corrects the change?
Insulin promotes glucose uptake and storage as glycogen. These changes remove glucose from blood, counteracting the rise.
Arrows show a causal sequence. They do not mean that a hormone turns into the substance named in the next box.
Explanation
After a carbohydrate-containing meal, absorption can raise blood glucose concentration. The pancreas releases more insulin. Insulin promotes glucose uptake by suitable target cells and the conversion of glucose into glycogen in the liver and muscle.
Uptake and storage remove glucose from blood, so blood glucose concentration falls towards its usual range. As the rise is corrected, the stimulus for extra insulin becomes smaller. The response counteracts the original change.
Between meals, blood glucose can fall. The pancreas releases more glucagon. Glucagon promotes conversion of stored glycogen to glucose in the liver, and the liver releases glucose into the blood.
This raises blood glucose towards its usual range. Insulin and glucagon therefore have opposing effects. Name the pancreas as the hormone source and the liver as a target; glycogen is not a hormone, and the liver releases glucose rather than whole glycogen molecules into blood.
Step by step
- 1
Choose the hormone
A rise stimulates more insulin; a fall stimulates more glucagon.
- 2
Explain target action
Name glucose uptake or glycogen formation for insulin, and liver glycogen breakdown for glucagon.
- 3
Return to the variable
State how blood glucose changes and why hormone secretion then decreases.
Worked example
Between meals
Blood glucose falls between meals. Outline a response that raises it towards normal.
One way to explain it
The pancreas releases more glucagon. Glucagon promotes the breakdown of liver glycogen to glucose. The liver releases glucose into the blood, raising blood glucose concentration.
Why this answer works
- A fall calls for a response that raises glucose.
- Name glucagon and its pancreatic source.
- Connect liver glycogen breakdown to glucose entering blood.
Watch out for this
A student says: "Insulin turns into glucose, while glucagon turns into glycogen." What is wrong with this?
Show the answer
Both are hormones that signal changes in target-cell activity. Glucose and glycogen are the substances interconverted during storage and release.
Check your understanding
Which response directly helps correct low blood glucose?
Show the answer
Glucagon promotes liver glycogen breakdown and glucose release.
The liver releases glucose, raising blood glucose towards its normal range.
Exam-style questions
Check your understanding
After a meal, a person's blood glucose rises from 5 to 8 mmol/dm3 and returns to 5 within two hours. Which hormone mainly brings it back down, and how?
Show the answer
Insulin, by making liver cells convert glucose to glycogen
Insulin is released when glucose rises and causes the liver to store glucose as glycogen.
Quick recall
How are a glucose rise and a glucose fall corrected?