Transport in Mammals

Name the valve labelled V on Fig. 3.1.

With reference to the chambers of the heart and the main blood vessels, describe the flow of blood through the heart that occurs when the transverse section of the heart appears as shown in Fig. 3.1.

Identify the stage of the cardiac cycle shown in Fig. 3.2.

Give a reason for your answer.

stage of cardiac cycle ______

reason ______

The rate and rhythm of the heartbeat are controlled by an area of specialised muscle tissue in the wall of the right atrium, called the sinoatrial node.

Describe the sequence of events that control contraction of the ventricles during the cardiac cycle.

Name the main artery serving the cardiac muscle from which the SN artery branches.

With reference to the role of the SAN, suggest how a slow rate of ventricular contraction could indicate that the SAN is not functioning correctly.

In people with Wolff–Parkinson–White syndrome, there is a bundle of fibres known as the bundle of Kent. These fibres can conduct impulses from the atria to the ventricles. This means that impulses do not always take the normal route through the AVN to the ventricles.

With reference to the role of the AVN, suggest and explain the change that occurs in the heart rate when impulses pass down the bundle of Kent to the ventricles instead of passing through the AVN.

Table 2.1 shows descriptions of three types of white blood cell.

Complete Table 2.1 by stating the names of these three types of white blood cell.

Table 2.1

Dromedary camels are classified in the family Camelidae and live in desert habitats of North Africa and Asia. In these hot, dry environments, dromedary camels can lose up to $30\%$ of their body mass from dehydration, causing their blood to become more viscous (thicker).

Fig. 2.1 shows a drawing of red blood cells of a dromedary camel. Fig. 2.2 is a drawing of human red blood cells.

Fig. 2.1 and Fig. 2.2 show differences between the red blood cells of dromedary camels and the red blood cells of humans.

Suggest how these differences adapt dromedary camels for living in hot, dry environments.

With reference to Fig. 2.3, explain how the differences between the oxygen dissociation curves for humans and llamas show that llamas are better adapted for living at high altitudes than humans.

Sketch a curve on Fig. 2.3 to show the effect of an increased carbon dioxide concentration on the percentage saturation of adult human haemoglobin with oxygen.

Explain the importance of the Bohr shift in metabolically active organs, such as the liver.

State the evidence, visible in Fig. 5.1, that identifies the cells inside the capillary as red blood cells.

Explain how the structure of the capillary wall is related to its functions.

An increase in respiration results in an increase in the carbon dioxide concentration in the blood and the release of more oxygen from red blood cells to tissues.

Explain how an increase in carbon dioxide in the blood leads to the release of more oxygen from red blood cells.

Chloride ions are a constituent of blood plasma. The concentration of chloride ions in the plasma of deoxygenated blood is between $2-4\ \text{mmol dm}^{-3}$ lower than in the plasma of oxygenated blood.

Explain why the concentration of chloride ions in the blood plasma of deoxygenated blood is lower than in the plasma of oxygenated blood.

Fig. 1.1 is a summary of blood flow through the right side of the heart during one cardiac cycle. Three boxes in Fig. 1.1 are not complete.

Complete boxes 3, 5 and 7 in Fig. 1.1 using only the terms systole and diastole.

Impulses sent out by the SAN pass to the AVN, where there is a short delay.

With reference to Fig. 1.1, explain why it is important for the control of the cardiac cycle that there is a short delay at the AVN after impulses have been sent out by the SAN.

Changes in blood pressure occur in the heart during the cardiac cycle. These changes cause the opening and closing of the bicuspid and tricuspid (atrioventricular) valves and the aortic and pulmonary (semilunar) valves.

Explain how blood pressure changes:

• cause the opening of the tricuspid valve
• cause the opening of the pulmonary valve
• help the flow of blood through the heart.

Explain why the ventricles have thicker walls than the atria.

Complete Table 6.1 to identify the structure in the heart responsible for each function listed.

Table 6.1

State the precise location in the heart of the sinoatrial node.

State the part of the cardiac cycle that is directly initiated by the wave of excitation sent out by the sinoatrial node.

Part of the control of the cardiac cycle involves the contraction of the ventricle walls after the walls of the atria have finished contracting.

Outline how this control is achieved.

Name the valves of the heart that open soon after the Purkyne tissue has received an impulse from the atrioventricular node.

Name:

• the two different circulations of the double circulatory system of mammals

• the main vein returning deoxygenated blood to the heart.

In a closed circulation, blood is kept within vessels at all times.

Name the type of blood vessel that connects capillaries and veins.

Fig. 1.1 is a diagram of a section through the heart.

On Fig. 1.1:

• add a label line and the letter L to show the artery that takes blood from the heart to the lungs
• add a label line and the letter R to show the valve that closes when the right ventricle is in systole.

The entry of carbon dioxide into red blood cells results in the production of hydrogencarbonate ions. This involves the enzyme carbonic anhydrase.

Complete the passage summarising the production of hydrogencarbonate ions by:

• writing the correct biological term in the spaces provided
• writing the molecular formula for two of the terms in the spaces in brackets.

Carbonic anhydrase has an overall spherical shape and is known as a ______ protein. The enzyme acts within the cell so can be described as an ______ enzyme. When blood passes into the capillary network through actively respiring tissues, carbon dioxide ($\text{CO}_2$) diffuses into red blood cells and carbonic anhydrase catalyses a reaction where ______ (______) is combined with $\text{CO}_2$ to form ______ ($\text{H}_2\text{CO}_3$), which rapidly forms ______ ions (______) and hydrogencarbonate ions ($\text{HCO}_3^{-}$).

Name stage B in Fig. 6.1 and state one piece of evidence from the diagram that supports your answer.

stage B ______

evidence ______

Draw a label line on Fig. 6.1 to identify one semilunar valve. Label the valve S.

Describe the role of the semilunar valves in the cardiac cycle.

Explain how the cells in the capillary shown in Fig. 3.1 can be identified as red blood cells.

Capillaries are surrounded by tissue fluid.

Outline the ways in which the composition of tissue fluid differs from blood.

Describe the changes in mean percentage saturation of haemoglobin with oxygen and the mean haemoglobin concentration in blood as altitude increases.

With reference to Table 3.1, suggest how the people living at high altitude can have an oxygen concentration in blood leaving the lungs similar to that of the people living at sea level.