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Transport · Paper 2 — Free Biology SL Practice Questions

1MasterySAQ-SBlood circulation in mammals (cardiovascular system)6 marksPaper 2~9 min

A patient is admitted to the emergency department with a suspected pulmonary embolism. A blood clot has lodged in a branch of the pulmonary artery, obstructing blood flow to a portion of the right lung.

(a)

State the type of blood vessel that carries oxygenated blood from the lungs to the heart, and name the heart chamber it empties into. [1 mark]

(b)

Calculate the stroke volume of the patient's heart. The cardiac output is

4.2\,\text{dm}^3\,\text{min}^{-1}

and the heart rate is

70\,\text{beats}\,\text{min}^{-1}

. [2 marks]

(c)

Explain why the oxygen concentration of blood arriving at the left atrium is lower than normal as a result of the pulmonary embolism. [3 marks]

Solutions

2MasterySAQ-SBlood circulation in mammals (cardiovascular system)5 marksPaper 2~8 min

A researcher measures blood pressure and blood velocity in different blood vessels of a mammalian circulatory system. Vessel — Systolic / diastolic pressure (mmHg) — Mean blood velocity (

\text{cm s}^{-1}

) Aorta — 120 / 80 — 40 Arteriole — 60 / 40 — 10 Capillary — 30 / 20 — 0.5 Venule — 20 / 15 Vena cava — 10 / 5 — 25

(a)

Describe the relationship between blood velocity and vessel type, and explain this pattern in terms of total cross-sectional area. [2 marks]

(b)

Calculate the pulse pressure in the aorta. [1 mark]

(c)

Explain how the structural features of capillary walls allow efficient exchange of substances between blood and tissues, and explain why a reduction in blood velocity at capillaries important for this exchange. [2 marks]

Solutions

3ChallengeSAQ-LRole of the heart and blood vessels7 marksPaper 2~11 min

A medical researcher is investigating a newly discovered mutation in the gene encoding connexin-43, a protein that forms gap junctions in the sinoatrial (SA) node and atrioventricular (AV) node of the human heart. The mutation causes a

40\%

reduction in the rate of ion flow through these gap junctions. A patient with this mutation has a resting heart rate of

72\,\text{bpm}

and a stroke volume of

70\,\text{mL}

. Reference values: - Normal PR interval:

0.12

–

0.20\,\text{s}

- Normal QRS duration:

< 0.12\,\text{s}

- Normal corrected QT interval:

< 0.44\,\text{s}

\text{CO} = \text{HR} \times \text{SV}

(a)

Calculate the cardiac output of this patient at rest. [1 mark]

(b)

Explain the likely effect of the mutation the PR interval seen in the patient's ECG. [2 marks]

(c)

During moderate exercise the patient's heart rate rises to

140\,\text{bpm}

and stroke volume increases by

15\%

from its resting value. In a healthy individual, stroke volume would increase by

40\%

from the same resting value at the same heart rate. Determine the patient's cardiac output during this exercise and the cardiac output a healthy individual would achieve under the same conditions. [2 marks]

(d)

Using your answer to (c) and your knowledge of cardiovascular physiology, evaluate whether the mutation is likely to limit the patient's maximum exercise capacity. [2 marks]

Solutions

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