How does the body control blood sugar level ?

For glucose level read 'the blood concentration of the sugar glucose' C₆H₁₂O₆

The pancreas is always checking on the concentration of glucose in the blood that flows through it.

 

(a) If your glucose level in the blood is too high the 1st hormone insulin is secreted by the pancreas.

After a meal the glucose concentration in the blood rises and insulin causes it to move into the cells in the body for respiration.

BUT, the insulin also causes cells in liver and muscle to convert some of the glucose into glycogen - an chemical energy store.

So, prompted by the pancreas detecting a high level of blood sugar, the insulin secreted promotes cellular uptake of glucose for respiration AND the formation of glycogen.

If the glucose concentration is too high, the pancreas secretes insulin.

Therefore, the conversion of glucose to glycogen, reduces the glucose concentration in the blood.

When the glucose level reduces, insulin is no longer secreted by the pancreas and the conversion of glucose to glycogen stops and the blood glucose level is stabilised.

 

(b) If the pancreas detects your blood glucose level is too low the 2nd hormone glucagon is secreted by the pancreas into the bloodstream.

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Key points Source of information is based on textbooks & syllabus-specifications for students taking the AQA GCSE, Edexcel GCSE and OCR GCSE level biology examinations (~US grades 9-10).

Key points about the negative feedback mechanism for controlling blood sugar levels

Revision notes for students on the negative feedback mechanism involving insulin and its role in blood glucose regulation.

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Negative Feedback & Blood Glucose Control

What Is Negative Feedback?

Negative feedback is a control system where a change in a condition triggers a response that reverses the change, helping to maintain a stable internal environment—a key part of homeostasis.

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Blood Glucose Regulation: The Role of Insulin

Why It Matters

Glucose is the body’s main energy source. Its concentration in the blood must be kept within a narrow range to:

• Provide energy for cellular respiration.

• Prevent damage from too much or too little glucose.

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The Negative Feedback Loop Involving Insulin

When Blood Glucose Is Too High (e.g. after eating)

1. Stimulus: Blood glucose concentration rises.

2. Receptor: The pancreas detects the increase.

3. Response:

   • The pancreas releases insulin.

   • Insulin travels in the blood to target organs (mainly liver and muscle cells).

   • These cells absorb glucose from the blood.

   • Excess glucose is converted into glycogen and stored in the liver and muscles.

4. Outcome: Blood glucose concentration falls back to normal.

This is a negative feedback loop because the response (lowering glucose) reverses the original change (high glucose).

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When Blood Glucose Is Too Low (e.g. after exercise)

1. Stimulus: Blood glucose concentration drops.

2. Receptor: The pancreas detects the decrease.

3. Response:

   • The pancreas releases glucagon (a different hormone).

   • Glucagon causes the liver to break down glycogen into glucose.

   • Glucose is released into the bloodstream.

4. Outcome: Blood glucose concentration rises back to normal.

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Why This Is Important in Human Biology

• Demonstrates how the endocrine system maintains internal balance.

• Shows how hormones like insulin and glucagon work in opposition to regulate a vital process.

• Helps explain conditions like diabetes:

  • Type 1: Pancreas doesn’t produce insulin.

  • Type 2: Body cells become resistant to insulin.

• Reinforces the concept of homeostasis and negative feedback in real-life health scenarios.

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Exam Tips

• Use key terms: insulin, glucagon, glycogen, negative feedback, homeostasis, pancreas.

• Be able to label diagrams or interpret graphs showing blood glucose changes.

• Compare responses in healthy individuals versus those with diabetes.

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Keywords, phrases and learning objectives for this part on the insulin negative feedback mechanism to control blood sugar level

In terms of homeostasis be able to describe and explain the negative feedback mechanism involving the hormone insulin, which is secreted from pancreas, and controls the concentration of glucose (for respiration) in the blood stream.

Be able to interpret the body's response (insulin feedback mechanism) from a diagram if the glucose level in the blood becomes too high or too low.

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