Blood glucose regulation (AQA GCSE Biology): Revision Notes
Blood glucose regulation
The pancreas controls blood glucose
The pancreas is the organ that watches and controls how much glucose is in your blood. It acts like a monitor, checking glucose levels all the time.
When glucose levels change, the pancreas responds by releasing hormones to fix the problem.
The pancreas functions as your body's glucose monitoring system, constantly sampling blood glucose levels and making adjustments to maintain balance.
What is insulin?
Insulin is a hormone that the pancreas makes. Think of insulin as a key that helps glucose get into cells.
What insulin does:
- Makes cells take up more glucose from the blood
- Causes blood glucose levels to drop
- Helps muscle cells and the liver store glucose
The main target organs for insulin are:
- Muscle cells - they absorb glucose for energy
- Liver cells - they store glucose as glycogen
Insulin is essential for moving glucose from the bloodstream into cells where it can be used for energy or stored for future use.
Storage of glucose
When we have too much glucose, our body stores it for later use.
How glucose gets stored:
- Muscle cells and liver cells convert glucose into glycogen
- Glycogen is made when many glucose molecules join together
- This stored glycogen can be broken down later when we need energy
Key fact: Animals store glycogen in their liver and muscle cells. Plants store starch in their cells instead.
How glucose control works
Blood glucose levels stay within a narrow, healthy range. This happens through negative feedback - when levels change, the body responds to reverse that change.
When blood glucose rises (after eating)
Worked Example: Blood Glucose Rising After a Meal
- Pancreas detects the rise in blood glucose
- Pancreas increases insulin production
- Insulin causes muscle and liver cells to remove glucose from blood
- Glucose gets stored as glycogen
- Blood glucose falls back to normal range
When blood glucose falls (after exercise)
Worked Example: Blood Glucose Falling After Exercise
- Pancreas detects the fall in blood glucose
- Pancreas decreases insulin production
- Less glucose gets absorbed by cells
- Blood glucose rises back to normal range
This negative feedback system ensures that blood glucose levels remain stable regardless of when you eat or exercise.
Example: Blood glucose after a meal
When someone eats a meal, their blood glucose changes in a predictable pattern:
- Point A (first hour): Glucose levels rise as food gets digested and absorbed
- Point B (after 2 hours): Glucose levels fall as insulin helps cells absorb the glucose
The glucose gets converted to glycogen for storage, bringing levels back to normal.
Key Points to Remember:
- The pancreas monitors blood glucose levels and releases insulin when needed
- Insulin is the hormone that lowers blood glucose by helping cells absorb it
- Muscle and liver cells are the main targets that take up glucose and store it as glycogen
- Negative feedback keeps glucose levels stable - changes trigger responses that reverse the change
- After eating, glucose rises then falls as insulin moves it into storage