Temperature regulation

4 (a) The diagram shows a section through the skin with some structures labelled.

Which structure is the sweat gland?

Which structure is a capillary?

Describe the changes that take place in the blood vessels in the skin if a person moves to a hot environment.

Scientists investigate the release of sweat from human skin when a person runs at different speeds. They measure the rate of sweating in litres per hour. They take measurements in two environments. The first environment is hot and humid, and the second environment is cool and dry. The graph shows the scientists’ results.

Give the dependent variable in this investigation.

A person runs at a speed of 220 metres per minute in hot and humid conditions. Calculate the volume of sweat the person releases in 15 minutes.

volume =_........

Using information from the graph, discuss the effect of increased running speed on sweating in the two environments.

Mammals, such as humans, need to regulate their internal environment.

What is the process that maintains a constant internal environment?

Table 1 shows the water input and output per day for a person in normal temperature conditions.

The water loss from gas exchange plus the loss from sweating are referred to as the insensible water loss. This water loss is called insensible because it cannot be measured directly.

Calculate the percentage of the water loss that is classified as insensible.

This data comes from a person who has a mass of 70 kg.

Assuming the same proportions, calculate the water input from food for a person who has a mass of 110 kg.

input from food =_........ litres

Water loss in faeces is usually relatively low.

Illness such as food poisoning can produce symptoms including vomiting, diarrhoea and a high temperature. These symptoms can change water balance in the body.

Explain how the symptoms of food poisoning can change water balance in the body.

The photograph shows a mammal called a degu.

(Source: © R. Maximiliane / Shutterstock)

A degu is a rodent that lives in a very dry environment in South America. The degu gets its water input by feeding on plants.

The water intake of the degu changes during the winter and summer months.

Table 2 shows the body mass, water intake and urine concentration of the degu in the winter and in the summer. It also shows the total rainfall in winter and in summer.

Comment on the differences in body mass, water intake and urine concentration in winter and summer.

Use the data in the table and your own knowledge in your answer.

The diagram shows a section of human skin with some structures labelled.

Which structure is a pore of a sweat gland?

Which structure carries blood?

The skin responds to changes in temperature.

Describe how the skin responds when a person enters a cold environment.

Scientists investigate the effect of heat strain on two groups of men.

Heat strain is caused by increasing the external temperature.

The scientists measure the skin temperature with no heat strain, low heat strain and moderate heat strain.

They also measure the rate of sweating with low and moderate heat strain.

The table shows the scientists’ results.

Discuss the relationship between age and the effect of heat strain on the mean skin temperature and the mean rate of sweating.

Use information from the table and your own knowledge in your answer.

The skin is an organ involved in temperature regulation.

State why the skin is described as an organ.

The diagram shows a section of human skin.

Explain how the skin capillaries regulate body temperature when the body temperature increases.

Some people have suggested that drinking warm drinks may cool the body because it increases the rate of sweat production.

Design an investigation to determine whether drinking warm drinks increases the rate of sweat production.

Include experimental details in your answer and write in full sentences.

Humans can control their internal environment.

State the term used to describe the control of an organism’s internal environment.

Coordination uses hormones and nerves.

Some responses are simple reflex arcs.

Describe the structure and functioning of the withdrawal reflex of a finger from a hot object.

Humans use their skin to regulate their body temperature. The diagram shows a section through the skin with two structures labelled A and B.

Changes take place in the skin when a person moves from a warm environment to a cold environment.

Explain the changes that take place in structure A as a person enters a cold environment.

Explain the changes that take place in structure B as the person enters a cold environment.

Modern humans have less body hair than their ancestors.

Explain how this evolutionary change was brought about by natural selection.

Farmers can keep their animals indoors or outdoors.

A student uses this apparatus to compare the heat loss from animals kept indoors and outdoors.

He uses a covered beaker to represent animals indoors and an uncovered beaker to represent animals outdoors.

This is the student’s method.

• pour 200 cm³ of hot water into each beaker

• measure the temperature of the water in each beaker

• cover one beaker with a cardboard box

• measure the temperature of the water in each beaker after 30 minutes

The student repeats the investigation six times and calculates the mean temperature of the water for each beaker.

The table shows the student’s results.

Give the dependent variable in this investigation.

Give one reason why the student uses the same volume of water in each beaker.

Calculate the difference between the percentage decrease in temperature for the uncovered beaker and the percentage decrease in temperature for the covered beaker.

The student concludes that it is better for farmers to keep their animals indoors.

Discuss this conclusion.

Describe how the student could modify his investigation to find out if an animal’s body size affects heat loss.

Arteries and veins are involved in the circulation of blood.

How do arteries differ from veins?

The diagram shows a section through a coronary artery from a person who has heart disease.

Using measurements from the diagram, calculate the percentage decrease in the diameter of the lumen where the fat deposit is thickest.

percentage decrease =_........ %

Explain how the fat deposit would affect the type of respiration in the heart muscle.

A high fat diet increases the risk of heart disease. Give two other factors that can increase the risk of heart disease.

Small arteries in the skin have a role in homeostasis. In an investigation, the diameter of a small artery in the skin is measured in a cold environment and then in a warm environment. The blood flow in this artery is also measured. The table shows the results.

Explain these changes in diameter and blood flow when moving from a cold environment to a warm environment.