Heart: Pressure Changes & Exercise Questions
1. (a) The graph shows pressure changes in the left ventricle, left atrium and aorta.
20
15
R
10QBlood
pressure / k Pa
5SP
0
–5
00.51.01.5Time / s
Left ventricle Left atrium Aorta
(i) Which letter on the graph corresponds to each of the following?
Letter
Aortic (semilunar) valve opens
Blood starts to enter the left ventricle
Bicuspid (atrioventricular) valve closes
(3)
(ii) Assuming a steady rate of beating of the heart, calculate the pulse rate per minute for this
person.
Answer: ................................. (1)
(b) Contraction of the heart muscle is described as being myogenic. (i) Explain what is meant by myogenic.
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(1)
(ii) How is contraction of muscle cells in the heart coordinated?
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(Total 7 marks)
2. A small tube called a catheter can be inserted into the blood system through a vein. It can be threaded through the vein and into and through the heart until its tip is in the pulmonary artery. A tiny balloon at the tip can then be used to measure the pressure changes in the pulmonary artery. The diagram shows a section through the heart with the catheter in place. The graph shows the pressure changes recorded in the pulmonary artery.
X
Pressure
Time
(a) Name the chamber of the heart labelled P.
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(1)
(b) Complete the table by placing ticks in the appropriate boxes to show which of valves 1 to 4 will
be open and which closed at time X on the graph.
Valve Open Closed
1
2
3
4
(2)
(c) Sketch a curve on the graph to show the pressure changes which you would expect if the
pressure in the aorta were measured at the same time.
(2)
(Total 5 marks)
3. The table shows the rate of blood flow to various parts of the body at rest and during vigorous
exercise
Rate of blood flowPart of body
at restduring vigorous exercise
Skeletal muscles100016 000
Heart muscle2501 200
Skin500750
Kidneys1000300
Liver and gut1250375
Brain750
(a) (i) Suggest suitable units for the rate of blood flow.
....................................................................................................................... (1)
(ii) Suggest a suitable value for the rate of blood flow to the brain during vigorous exercise.
Give a reason for your answer.
Value ................................................................................................................
Reason ..............................................................................................................
........................................................................................................................... (2)
(b) The blood flow to the skeletal muscles changes during vigorous exercise. Describe the part
played by each of the following in bringing about this change:
(i) the nerves going to the sinoatrial node in the heart;
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(ii) the arterioles taking blood to the skeletal muscles.
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........................................................................................................................... (2)
(c) Use information from the table to suggest why it is recommended that vigorous exercise should
not be undertaken until at least two hours after a meal.
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..................................................................................................................................... (1)
(Total 8 marks)
4. The graph shows changes in the volume of blood in the left ventricle as the heart beats.
140
A
120
100
Volume /3cm
80
60
00.20.40.60.81.01.21.40
Time / s
(a) (i) The horizontal line labelled A on the graph shows when blood is leaving the ventricle.
Explain, in terms of blood pressure, why blood does not flow back into the atrium during
this period.
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(2)
(ii) Draw a horizontal line on the graph, to show the period in one cardiac cycle when the
muscle in the wall of the ventricle is relaxed. Label this line with the letter B.
(1)
(b) (i) Draw a horizontal line on the graph to show one complete cardiac cycle. Label this line
with the letter C.
(1)
(ii) Use line C to calculate the number of times the heart beats in one minute. Show your
working.
Answer ...................................
(2)
(c) The table shows the blood flow to different parts of the body at rest and during a period of vigorous exercise.
3 1 Rate of blood flow/cmminute–Part of the body
at rest during exercise
Brain 750 750
Heart muscle 300 1 200
Gut and liver 3 000 1 400
Muscle 1 000 16 000
All other organs (except lungs) 1 550 1 550
(i) Use the figures in the table to calculate the cardiac output at rest.
Answer ...................................
(1)
(ii) Give two ways in which cardiac output is increased during a period of vigorous exercise.
1.........................................................................................................................
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2.........................................................................................................................
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(2)
(d) Describe the parts played by the sinoatrial node (SAN) and the atrioventricular node (AVN) in controlling the heart beat.
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(6)
(Total 15 marks)