The Circulatory System (Edexcel A (SNAB) AS Biology)

The diagram shows an image of a micrograph of a cross section through two mammalian blood vessels.

 Identify the the type of blood vessels labelled X and Y.

(2)

Describe one structure of each vessel and explain how this structure relates to its function.

(2)

The graph below shows pressure changes in the blood vessels as the blood passes through different sections of the mammalian circulatory system.

Explain the blood pressure in the following sections of the graph:

The arteries and arterioles

(3)

The capillaries

(1)

The venules and veins

(1)

The main component of both blood and tissue fluid is water.

Explain one property of water that makes it an ideal transport medium for organisms with a transport system.

Explain the role of hydrogen bonding and its importance in transporting water.

Water is described as a dipole in nature.

With reference to covalent bonding, explain the dipolar nature of water molecules.

The graph below shows changes in pressure in parts of a human heart during one second.

State the time at which the semi-lunar valves open.

Use the graph to calculate the heart rate in beats per minute (bpm).

Valves are important for maintaining blood pressure in the heart. 

Using a specific example, explain how they work.

The contractions of the heart muscle leading to pressure changes.

Name which part of the heart causes the increase in pressure in the aorta.

(1)

Explain why this increase is important for the organism.

(3)

A group of scientists were investigating heart rate. The scientists used Daphnia fleas to find out the effect of Sotalol beta blocker on heart rate. 

The Daphnia were divided into two groups: one group was administered Sotalol every day for 7 seven days. The other group acted as a control. The scientists measured the heart rates of both sets of the Daphnia after exposure to the drug or control substance.

Describe how the control group should have been treated. 

Using live organisms during experimentation raises some ethical issues.

Discuss the ethical issues when using organisms such as Daphnia.

(2)

Name two precautions that should be taken when using live organisms in experimentation.

(2)

The scientists then investigated how changing the concentration of Sotalol affected the heart rate of Daphnia.

The table below shows their results. 

Calculate the percentage decrease in the heart rate of Daphnia for increasing concentration of Sotalol from 0% to 20%.

(2)

The scientists used the percentage change in the heart rate of Daphnia to compare the results for the control group and experimental group.

Explain why they used percentage change as part of their analysis.

(2)

After reading the scientists’ report, a journalist reported that:

"Sotalol: The next best drug for your heart: Beta blockers decrease heart rate!”

Evaluate this statement.