(2.1) Sugar level control - Why the need to control the concentration of blood glucose?

Introduction reminder: Homeostasis is all about controlling conditions in the human body.

Homeostasis is a word that is sometimes used to describe your bodily functions that try to maintain a stable constant internal environment including the factors listed above.

Therefore you need to know internal conditions controlled include blood sugar (usually glucose) level.

The blood sugar levels must be adequate to provide the cells with a constant supply of energy to meet their needs, but not to high to cause problems, some health issues are described below.

Having too much glucose in your blood for long periods of time can cause serious health problems if it's not treated. This condition is called hyperglycemia and can damage the vessels that supply blood to vital organs, in turn this can increase the risk of heart disease and stroke, kidney disease, vision problems, and nerve problems.

When sugary or carbohydrate foods are digested in the small intestine, the blood sugar levels rise as the sugar is absorbed from the gut into the bloodstream.

Your normal cell metabolism uses and removes the sugar in your normal energy releasing chemistry - respiration.

If you are not doing much physical work your blood sugar level will tend to rise.

Insulin reduces the concentration of glucose in your blood.

Lack of insulin can lead to dangerously high glucose levels in your blood.

Excess glucose can be to glycogen and stored in the liver and in your muscles, the glycogen which can be converted back to glucose for use during exercise.

When the glycogen stores are 'full', the excess glucose is converted to, and stored as, lipid fats.

If you are doing some demanding physical exercise your blood sugar level tends to fall as the sugar is consumed.

During exercise a number of changes take place e.g. the heart rate increases and the rate and depth of breathing increases.

These changes increase the blood flow to the muscles and so increase the supply of sugar and oxygen for energy from respiration and also increase the rate of removal of carbon dioxide - the waste product.

Glycogen is produced and stored and released for conversion to glucose on a supply and demand basis.

If there is surplus glucose and physical activity is low, more glycogen is produced.

The more you physically exercise, the greater the glucose demand, if this exceeds what is available in the blood stream, then the glycogen reserves are called upon to fill the energy gap.

 

The blood glucose level is monitored and controlled by the pancreas which produces the hormone insulin.

The pancreas secretes enzymes that digest carbohydrates, proteins and lipid fats.

It can be dangerous if your blood sugar levels become too high or too low, so your blood sugar level is regulated by the hormone insulin made in the pancreas, which enables your body to have a regular supply of sugar for energy from respiration.

Changes in the blood glucose level are monitored by the pancreas, which produces the hormone insulin, which allows the glucose to move from the blood into the cells and stored as glycogen.

A second hormone, glucagon, is produced in the pancreas when blood glucose levels fall.

Glucagon causes glycogen to be converted back into glucose and released into the blood for respiration.

 

So, the level of glucose in the blood must be kept steady and your automatic monitoring systems keeps a check on any changes.

This is done by the pancreas using the hormones insulin and glycogen in a negative feedback cycle.

 

Note that the metabolism of glucose is controlled by three hormones, here it is insulin and glucagon maintaining the balanced level of glucose in the blood, but there is also the action of adrenaline on the liver in our body's 'fight or flight' response.

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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 ideas about controlling the concentration of sugar in our blood

Biology notes for students on why we need to control blood sugar levels and how it links to understanding human biology.

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Why Do We Need to Control Blood Sugar Levels?

Blood glucose (sugar) is the main fuel for cellular respiration, especially in the brain and muscles. However, its concentration in the blood must be kept within a narrow range to avoid serious health problems.

The Importance of Regulation

Maintaining a stable blood glucose level is part of homeostasis—the body’s way of keeping internal conditions constant.

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How Is Blood Glucose Controlled?

The pancreas monitors blood glucose and releases hormones to adjust it:

Hormone	Released When...	Function
Insulin	Blood glucose is too high	Stimulates cells to absorb glucose; converts excess glucose to glycogen for storage.
Glucagon	Blood glucose is too low	Stimulates liver to break down glycogen into glucose and release it into the blood.

These hormones work in a negative feedback loop to maintain balance.

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Why Is This Important in Human Biology?

1. Energy Supply

• Glucose is essential for cellular respiration, which powers all bodily functions.

• The brain relies almost entirely on glucose for energy.

2. Preventing Disease

• Poor glucose control can lead to diabetes:

  • Type 1: Pancreas doesn’t produce insulin.

  • Type 2: Body cells become resistant to insulin.

• Long-term high glucose levels can damage:

  • Eyes (retinopathy)

  • Kidneys (nephropathy)

  • Nerves (neuropathy)

  • Heart and blood vessels (cardiovascular disease)

3. Homeostasis in Action

• Blood glucose regulation is a classic example of homeostasis.

• It shows how the body uses hormones, feedback systems, and organ coordination to maintain health.

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Exam Tips

• Use key terms like insulin, glucagon, glycogen, negative feedback, and homeostasis.

• Be able to interpret graphs showing blood glucose changes after eating or exercise.

• Compare responses in healthy individuals versus those with diabetes.

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Keywords, phrases and learning objectives for this part on ?

Homeostasis and glucose - be able to explain why the body needs to control the concentration of blood glucose.

Know that the hormone insulin controls the blood glucose level, otherwise there health issue problems if there is too much glucose in blood.

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