What do the coronary arteries supply?

The heart muscle, with oxygen and glucose.

Why is the wall of the left ventricle thicker than the right?

It pumps blood at higher pressure around the whole body, not just to the nearby lungs.

What closes the atrioventricular valves?

Ventricular pressure becoming higher than atrial pressure.

What opens the semilunar (aortic) valve?

Ventricular pressure becoming higher than pressure in the aorta.

What happens during diastole?

The heart relaxes, the semilunar valves close, the atria fill and the AV valves open.

State the equation for cardiac output.

Cardiac output = stroke volume × heart rate.

How do you calculate heart rate from the length of a cardiac cycle?

60 ÷ the cycle time in seconds.

Name four risk factors for cardiovascular disease.

High blood pressure, smoking, high blood cholesterol or saturated fat diet, lack of exercise (also obesity, age, genetics).

Why does a correlation not prove a cause?

A confounding variable may affect both factors, so the link could be due to something else.

How should conflicting evidence from two studies be evaluated?

Compare sample size, duration, control of variables, and whether results are significant.

The heart and cardiac cycleAQA A-Level Biology: Flashcards

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Which vessel carries blood into the right atrium?

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Which vessel carries blood into the right atrium?: The vena cava.
Which vessel carries blood from the right ventricle to the lungs?: The pulmonary artery.
Which vessel brings blood from the lungs to the left atrium?: The pulmonary vein.
Which vessel carries blood from the left ventricle to the body?: The aorta.
What do the coronary arteries supply?: The heart muscle, with oxygen and glucose.
Why is the wall of the left ventricle thicker than the right?: It pumps blood at higher pressure around the whole body, not just to the nearby lungs.
What closes the atrioventricular valves?: Ventricular pressure becoming higher than atrial pressure.
What opens the semilunar (aortic) valve?: Ventricular pressure becoming higher than pressure in the aorta.
What happens during diastole?: The heart relaxes, the semilunar valves close, the atria fill and the AV valves open.
State the equation for cardiac output.: Cardiac output = stroke volume × heart rate.
How do you calculate heart rate from the length of a cardiac cycle?: 60 ÷ the cycle time in seconds.
Name four risk factors for cardiovascular disease.: High blood pressure, smoking, high blood cholesterol or saturated fat diet, lack of exercise (also obesity, age, genetics).
Why does a correlation not prove a cause?: A confounding variable may affect both factors, so the link could be due to something else.
How should conflicting evidence from two studies be evaluated?: Compare sample size, duration, control of variables, and whether results are significant.

Exam questions on The heart and cardiac cycle

In a resting adult, the pressures in the left atrium, left ventricle and aorta are recorded throughout the cardiac cycle. At one moment, contraction of the ventricles has just begun: the pressure in the left ventricle has risen above the pressure in the left atrium, but is still lower than the pressure in the aorta.
Explain why blood does not flow back from the left ventricle into the left atrium while the ventricle contracts.2 marks
A man at rest has a heart rate of 68 beats per minute and a stroke volume of 75 cm³. After several months of endurance training, his resting heart rate falls to 55 beats per minute, while his resting cardiac output stays the same.
Explain how his resting heart rate can fall without any fall in cardiac output.2 marks
One cardiac cycle in a resting person lasts 0.80 s. The ventricles begin to contract at 0.10 s, when the pressure in the left ventricle first exceeds that in the left atrium. The pressure in the aorta at this time is 10.7 kPa. The pressure in the left ventricle exceeds this at 0.18 s, reaches a maximum of 16.0 kPa at 0.28 s, and falls back below the aortic pressure at 0.42 s.
Calculate the heart rate in beats per minute and the length of time for which the aortic valve is open during one cycle.3 marks

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Written by the Exaim team, led by Shaun Daswani (Head of Upper Secondary, Improve ME Institute; MSc Financial Mathematics, Imperial College London; BSc, UCL) and Jason Daswani (operational lead, Improve ME Institute; LSE).