Homeostasis -  control of blood sugar level - insulin and diabetes

See also homeostasis - water content control - urea - kidney function

See also homeostasis - thermoregulation and temperature control

Doc Brown's Biology Revision Notes

Suitable for GCSE/IGCSE/O level Biology/Science courses or equivalent

This page will help you answer questions like e.g.

How does the body regulate temperature?

How does the body control blood sugar level

What is insulin? What does it do?



Homeostasis control 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.

Know that internal conditions that are controlled in the body include blood sugar level.


 

Sugar level control - the need to control the concentration of blood glucose

The blood sugar levels must be adequate to provide the cells with a constant supply of energy to meet their needs.

When sugary or carbohydrate foods are digested 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.

Excess glucose can be stored as glycogen in the liver and in your muscles.

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.

The muscles store glucose as glycogen, which can then be converted back to glucose for use during exercise.

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.

 

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, which enables your body to have a regular supply of sugar for a secure supply of energy.

The pancreas produces the hormone insulin, which allows the glucose to move from the blood into the cells.

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

This causes glycogen to be converted into glucose and be released into the blood.

 

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 glucogen in a negative feedback cycle - next section.

 


The mechanism of controlling the concentration of blood glucose

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

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

Insulin makes the liver turn glucose into glycogen.

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 your glucose level is too low the 2nd hormone glucagon is secreted by the pancreas.

Glucagon makes the liver convert glycogen into glucose.

So the blood level of glucose increases.

When the glucose concentration reaches an appropriate level, secretion of glucagon stops and so does the conversion of glycogen to glucose stabilising the glucose level.

 

The homeostasis negative feedback system for glucose level control

(a) The homeostasis negative feedback system for too high a glucose level - insulin is added (b) The homeostasis negative feedback system for too low a glucose level - glucogen added
1. The pancreas detects the blood sugar level is too high. 1. The pancreas detects the blood sugar level is too low.
2. Insulin is secreted by the pancreas to mix with the excess glucose. 2. Glucogen is secreted by the pancreas.
3. The excess glucose is now moved from the blood into liver and muscle cells. 3. There is too little glucose but there is glycogen stored in the liver
4. The glucose level is now reduced. 4. The secreted glucogen triggers the breakdown of glycogen into glucose sugar - using the liver's energy store.
5. The secreted insulin makes the liver turn the excess glucose into glycogen - effectively a store of chemical energy for future use. 5. The glucose level is increased in the blood to meet the respiration demands of the body.
This is all automatically done by the organism's complex control systems and enables the organism e.g. your body, to maintain as near as possible the 'ideal' glucose level for healthy life!

BUT it all depends on insulin production - and there may be diabetic problems - read on

 

 


Diabetes - problems with insulin and how to regulate it if need be

 

Type 1 Diabetes

Type 1 diabetes is a disease in which a person’s blood glucose concentration may rise to a high level because the pancreas does not produce enough of the hormone insulin.

Type 1 diabetes is caused by a lack of insulin, the hormone which controls the level of glucose in the blood - too little may be produced or non at all - a potentially dangerous situation.

This causes the blood glucose level to rise to potentially lethal levels.

Type 1 diabetes may be controlled by careful attention to diet, exercise, and by injecting insulin usually into the subcutaneous fat.

Type 1 diabetes can be controlled by two strategies, and both may be required ..

(i) Avoid too much sugary foods and carbohydrates in the diet, sugars in particular, will cause a rapid rise in glucose levels which is difficult to remove without the presence of sufficient insulin.

(ii) Insulin therapy - injecting insulin, perhaps several times a day at meal times, which will make the liver remove excess glucose from the digested food - this makes sure the excess glucose is converted to glycogen, reducing the concentration in the blood.

This is an inconvenient, but very effective way, of keeping the blood sugar level in check.

In Type 1 diabetes, the level of physical activity and diet affect the amount of insulin required.

The amount of insulin required by injection depends on the person's diet and level of activity.

A diabetic should minimise food rich in simple carbohydrates which can cause quite a rapid increase in blood sugar.

As well as controlling carbohydrate intake, taking regular exercise helps to use up some of the excess glucose from the blood.

 

Insulin injections can greatly help diabetics in providing the necessary insulin but it can never be as successful as a properly functioning normal pancreas and diabetics can suffer from long-term health problems.

A healthy balanced diet, regular eating and regular exercise will both help to keep a diabetic in good health and minimise the amount of insulin needed.

Diabetics can have a pancreas transplant which, if successful, can theoretically avoid the need for insulin, but there is always the danger tissue rejection and costly immunosuppressive drugs must be taken (with the added complication of serious side-effects).

 

Footnote on source insulin

Insulin was once extracted from the pancreas of a pig or cow, but human insulin is now made genetic engineering and doesn't give the side effects experienced from patients using animal insulin.

I remember a class debate on the merits and ethical issues concerning the use of genetic modification (GM) engineering. A diabetic in the class took to task another student trying to take the 'moral high ground' in arguing how wrong it was to use GM for medical purposes (or any other purpose - on the grounds it was interfering with nature). So, can I please point out the millions of diabetic patients around the world whose lives are so much more improved by a 'slow release' genetic modification of the hormone insulin.

 


Type 2 Diabetes

Type 2 diabetes is caused by a person becoming resistant to their own insulin.

The type 2 diabetes condition is

(i) when the pancreas doesn't make enough insulin or

(ii) the person has become resistant to insulin so the body doesn't even respond appropriately to any of the hormone insulin present,

and both will cause the blood sugar level to rise to potentially lethal levels.

Type 2 diabetes can be controlled by eating a healthy balanced diet, regular eating, regular exercise and losing weight if necessary.

Being overweight increases your chance of developing type 2 diabetes, obesity is considered to be potentially a major risk factor in the onset of diabetes disease.

Type 2 diabetes patients should make an effort to control the amount of carbohydrates in their food and take regular exercise - both strategies can help reduce the glucose sugar level in the blood.

Some Type 2 diabetics take insulin to help control this diabetic condition - but insulin therapy is more associated with type 1 diabetes.

 

There is some correlation between obesity and Type 2 diabetes.

Obese people (BMI > 30) do run the risk of developing type 2 diabetes and if their BMI is over 30, then action should be taken.

Body Mass Index (BMI) = (body mass in kg) / (height in m)2


Practical work in to help develop your skills and understanding may have included the following:

demonstrating blood testing (using meters)

Be able to evaluate modern methods of treating diabetes.

 


 

Homeostasis notes index:

Homeostasis - introduction to how it functions (negative feedback systems explained)

Homeostasis - control of blood sugar level - insulin and diabetes

Homeostasis - osmoregulation, ADH, water control, urea and ion concentrations and kidney function, dialysis

Homeostasis - thermoregulation, control of temperature

 


IGCSE revision notes control of blood sugar levels insulin diabetes KS4 biology Science notes on control of blood sugar levels insulin diabetes GCSE biology guide notes on control of blood sugar levels insulin diabetes for schools colleges academies science course tutors images pictures diagrams for control of blood sugar levels insulin diabetes science revision notes on control of blood sugar levels insulin diabetes for revising biology modules biology topics notes to help on understanding of control of blood sugar levels insulin diabetes university courses in biological science careers in science biology jobs in the pharmaceutical industry biological laboratory assistant apprenticeships technical internships in biology USA US grade 8 grade 9 grade10 AQA GCSE 9-1 biology science notes on control of blood sugar levels insulin diabetes GCSE notes on control of blood sugar levels insulin diabetes Edexcel GCSE 9-1 biology science notes on control of blood sugar levels insulin diabetes for OCR GCSE 9-1 21st century biology science notes on control of blood sugar levels insulin diabetes OCR GCSE 9-1 Gateway  biology science notes on control of blood sugar levels insulin diabetes WJEC gcse science CCEA/CEA gcse science Be able to explain how blood glucose levels are regulated by insulin and excess blood glucose is converted to glycogen in the liver The blood sugar levels – to provide the cells with a constant supply of energy. When sugary or carbohydrate foods are digested the blood sugar levels rise as the sugar is absorbed from the gut into the bloodstream. Your normal cell metabolism uses, and hence removes, the sugar in your normal energy releasing chemistry. If you are not doing much physical work your blood sugar level will tend to rise. If you are doing some demanding physical exercise your blood sugar level tend to fall as the sugar is consumed. 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, which enables your body to have a regular supply of sugar for a secure supply of energy. During exercise a number of changes take place eg 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. The muscles store glucose as glycogen, which can then be converted back to glucose for use during exercise. 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.  blood glucose regulation This regulates the concentration of glucose (needed constantly for energy from respiration) in the blood stream. The blood sugar levels – to provide the cells with a constant supply of energy. When sugary or carbohydrate foods are digested the blood sugar levels rise as the sugar is absorbed from the gut into the bloodstream. Your cell metabolism uses and hence removes the sugar in your normal energy releasing chemistry. If you are not doing much physical work your blood sugar level will tend to rise. If you are doing some demanding physical exercise your blood sugar level tend to fall. 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, which enables your body to have a regular supply of sugar for a secure supply of energy. Be able to explain how blood glucose levels are regulated by glucagon causing the conversion of glycogen to glucose If your glucose level in the blood is too high the 1st hormone insulin is secreted by the pancreas. Insulin makes the liver turn glucose into glycogen. 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. Insulin was once extracted from the pancreas of a pig or cow, but human insulin is now made genetic engineering and doesn't give the side effects experienced from patients using animal insulin. If your glucose level is too low the 2nd hormone glucagon is secreted by the pancreas. Glucagon makes the liver convert glycogen into glucose. So the blood level of glucose increases. When the glucose concentration reaches an appropriate level, secretion of glucagon stops and so does the conversion of glycogen to glucose stabilising the glucose level. Type 1 diabetes is a disorder in which the pancreas fails to produce sufficient insulin. It is characterised by uncontrolled high blood glucose levels and is normally treated with insulin injections. In Type 2 diabetes the body cells no longer respond to insulin produced by the pancreas. A carbohydrate controlled diet and an exercise regime are common treatments. Obesity is a risk factor for Type 2 diabetes. You should be able to compare Type 1 and Type 2 diabetes and explain how they can be treated. You should be able to extract information and interpret data from graphs that show the effect of insulin in blood glucose levels in both people with diabetes and people without diabetes. If the blood glucose concentration is too low, the pancreas produces glucagon that causes glycogen to be converted into glucose and released into the blood. You should be able to explain how glucagon interacts with insulin in a negative feedback cycle to control blood glucose (sugar) levels in the body. Be able to evaluate information around the relationship between obesity and diabetes, and make recommendations taking into account social and ethical issues.

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