Homeostasis is one of the most important processes within the human body.

What is homeostasis?

Using an example, explain why homeostasis is important in humans. 

The control of internal body temperature involves negative feedback.

Describe what is meant by negative feedback.

In humans, when body temperature drops below 35°C, positive feedback causes a continued decrease in body temperature.

This process is referred to as hypothermia.

Explain how positive feedback accelerates the process of hypothermia.

Homeostasis involves the process of positive feedback.

Describe what is meant by positive feedback.

Homeostasis also involves negative feedback.

Describe how a negative feedback mechanism works.

The diagram below shows the system that controls the concentration of the hormones testosterone in a man’s body.

The concentration of testosterone in the body is controlled by negative feedback.

Use information from the diagram above to explain why this is negative feedback.

The diagram below shows some of the events responsible for maintaining blood glucose concentration.

Name hormones A and B in the diagram above.

Name organ C in the diagram above.

Explain how hormone A leads to a decrease in blood glucose concentration.

Use the diagram above to explain why the events controlling blood glucose concentration can be described as an example of negative feedback.

The regulation of blood glucose concentration involves the secretion of hormones from the pancreas.

Name the endocrine tissue in the pancreas that secretes hormones.

Name the type of cell that secretes the hormone insulin.

Describe the role of the hormone glucagon in the control of blood glucose.

Adrenaline is another hormone involved in the control of blood glucose.

Explain how adrenaline causes an increase in blood glucose concentration.

A group of scientists inserted an artificial gene that codes for the hormone insulin into mice with type 1 diabetes.

The scientists measured the blood glucose concentration of each mouse at regular intervals and found that while the mice produced insulin, their blood glucose concentration was normal.

The mice continued to produce insulin for up to 9 months and showed no obvious side effects.

Explain why this type of treatment is less likely to work in mice with type 2 diabetes.

When measuring the blood glucose concentration of each mouse, the scientists made sure they were not fed for 8 hours before measurement.

Suggest why.

During the 9 months for which the mice produced insulin, explain how a high blood glucose concentration would be returned to normal.

Some researchers have suggested that this treatment should be provided to humans with type 1 diabetes.

Evaluate this suggestion.

Gestational diabetes is a type of diabetes resulting in high levels of blood glucose during pregnancy.

During gestational diabetes, the body produces normal levels of insulin.

Describe two ways in which gestational diabetes is similar to type 2 diabetes.

Metformin is a drug that can be used to help manage type 2 diabetes.

Metformin works by increasing a cell’s sensitivity to insulin and inhibiting adenylyl cyclase.

Explain how increasing a cell’s sensitivity to insulin helps to reduce blood glucose levels.

Explain how the inhibition of adenylyl cyclase helps to reduce blood glucose levels.

Other than metformin, suggest two ways in which type 2 diabetes can be managed.

When insulin binds to receptors on the surface of liver cells, it stimulates the formation of glycogen from glucose.

As a result, blood glucose concentration is reduced.

Explain how the formation of glycogen in liver cells results in a reduction in blood glucose concentration.

Diabetes is a condition in which the body cannot control blood glucose levels.

Doctors can use a glucose tolerance test to help diagnose patients with this condition.

They measure a person’s blood glucose concentration after a period of fasting.

The person then drinks a glucose solution and stays at rest before the doctor measures their blood glucose concentration again 2 hours later.

Why is it important that the patient stays at rest during the glucose tolerance test?

There are two types of diabetes: type 1 and type 2.

Type 1 diabetes is often referred to as insulin-dependent diabetes.

Suggest why.

Type 2 diabetes occurs when body cells do not respond to the hormone insulin.

Explain how this leads to uncontrolled levels of blood glucose.

A scientist investigated how the blood glucose concentration of a patient with type 1 diabetes changed over time.

A man with type 1 diabetes drank a glucose solution and his blood glucose concentration was measured at regular intervals.

The results are shown in the diagram below.

Sketch a curve on the graph below to show the results you would expect if this investigation was repeated with a patient without diabetes.

The patient’s blood glucose concentration was 90 mg per 100 cm³ before drinking the glucose solution.

The diabetic man involved in the investigation injects insulin once at breakfast and once in the evening.

His first injection of the day contains both slow-acting and fast-acting insulin.

Suggest the advantage of injecting both types of insulin at the start of the day.

Other than insulin injections, give one way in which people with type 1 diabetes can control their blood glucose concentration.

Describe the effects of insulin on its target tissues and explain how this affects blood glucose concentration.

The diagram below shows how the concentration of glucose in the blood changes following a meal.

Write the letters I and G on the graph to show a time when insulin (I) and glucagon (G) secretion would be high.

Describe the role of the hormone glucagon in the process of gluconeogenesis.

Use the diagram and your own knowledge to explain how negative feedback is used to control blood glucose concentration.

The diagram below shows how the concentrations of insulin and glucose change following a meal.

A glucose biosensor was used to measure blood glucose concentration.

Suggest two reasons why the use of a biosensor is more accurate than using the Benedict’s test to measure glucose concentration

After eating a meal, the concentrations of both glucose and insulin increase.

There is a slight delay between the increase of blood glucose concentration and the increase of insulin concentration.

Explain why.

A patient is having difficulty controlling their blood glucose concentration and may need to be treated with glucagon injections.

Give an example of why they may need glucagon injections.

Explain how glucagon is involved in the maintenance of blood glucose concentration.