Biology · Simulation and virtual lab Free
The heart: cardiac cycle, valves and exercise
Watch the valves open and shut during each heartbeat, then exercise to see how the heart pumps more blood.
- You will learn to
- Describe the sequence of the cardiac cycle and the role of the valves.
- Relate valve opening and closing to pressure changes in the heart.
- Calculate cardiac output and explain the effects of exercise and training.
- You will measure
- Heart rate (beats/min), stroke volume (cm³) and cardiac output (dm³/min) at each exercise level.
- Time needed
- About 30–40 min
- Equipment
- Nothing extra. Real version: stopwatch, step or bench, learners’ own pulse; a sheep or goat heart for dissection.
- Price
- Free: no payment, no account.
Virtual lab
Follow the steps with the simulation above (go back to the simulation ↑). Each time you tap Record, a row is added to the table and a point to the graph.
Aim
To describe the sequence of events in the cardiac cycle, to relate the opening and closing of the valves to pressure changes, and to investigate how exercise and training affect heart rate, stroke volume and cardiac output.
What to do
- Watch one heartbeat in slow motion. Name the stage when the atria contract and when the ventricles contract.
- Watch the valves. When are the valves between the atria and ventricles shut? When are the semilunar valves open?
- On the pressure graph, find the point where the ventricle pressure rises above the aorta pressure. What happens to the semilunar valve?
- At rest, tap Record. Then set exercise to 25 %, 50 %, 75 % and 100 %, waiting each time for a steady pulse, and record.
- Choose the athlete and repeat. Compare the graphs of cardiac output against heart rate.
- Tap Stop exercising and watch the pulse fall. Whose pulse returns to rest faster?
Results
Questions
Name the four chambers of the heart.
Right atrium, right ventricle, left atrium and left ventricle.
Why is the wall of the left ventricle thicker than the right?
It pumps blood all around the body at high pressure; the right ventricle only pumps to the nearby lungs.
What causes the "lub" and "dub" sounds?
Lub: the valves between the atria and ventricles shutting as the ventricles contract. Dub: the semilunar valves shutting as the ventricles relax.
What is the function of the valves?
To stop blood flowing backwards, so it flows in one direction only.
Calculate the cardiac output when the heart rate is 70 beats per minute and the stroke volume is 75 cm³.
Cardiac output = 70 × 75 = 5 250 cm³ per minute ≈ 5.3 dm³/min.
Why does an athlete have a lower resting heart rate?
Training makes the heart muscle bigger and stronger, so it pumps a larger stroke volume and needs fewer beats for the same cardiac output.
For teachers: expected results and how the model works
Pressures (left side, mmHg) are a simplified model: ventricle 6 → 120, aorta about 80–120 with a dicrotic notch, atrium 5–11. Valves open by pressure difference: the atrioventricular valve when atrium > ventricle, the semilunar valve when ventricle ≥ aorta. Model hearts: student rests at 72 beats/min with 70 cm³ (5.0 dm³/min); athlete rests at 55 beats/min with 92 cm³ (5.1 dm³/min). Heart rate rises linearly with exercise to 195 at 100 %; stroke volume rises to its maximum (105 cm³ student, 150 cm³ athlete) by 50 % exercise. At 50 %: student about 134 beats/min, 14 dm³/min; athlete 125 beats/min, 19 dm³/min. At 100 %: 20.5 and 29.3 dm³/min. The pulse returns to rest about twice as fast for the athlete. Real learners can measure their own resting pulse, then after 2 minutes of step-ups, and every 30 s during recovery.
Exam practice Exam set
National-exam style questions on this simulation (15 marks). Try each one on paper first, then open the marking scheme.
Describe the events of the cardiac cycle, starting from when the atria contract. (5 marks)
Marking scheme: Atria contract, pushing blood into the ventricles (1); ventricles contract and pressure rises, closing the atrioventricular valves (1); semilunar valves open and blood is pumped into the aorta and pulmonary artery (1); ventricles relax and the semilunar valves close (1); blood flows from the veins into the atria and ventricles (diastole) (1).
During exercise a student’s heart rate rose from 72 to 150 beats per minute and the stroke volume from 70 to 105 cm³. Calculate the cardiac output before and during exercise and the percentage increase. (5 marks)
Marking scheme: Before: 72 × 70 = 5 040 cm³/min (1); during: 150 × 105 = 15 750 cm³/min (2); increase = (15 750 − 5 040) ÷ 5 040 × 100 (1) = 213 % (1).
Explain why the heart rate increases during exercise. (3 marks)
Marking scheme: Muscles respire faster and need more oxygen and glucose (1) and must remove more carbon dioxide (1); a higher heart rate pumps more blood to them per minute (1).
On a pressure graph of the left side of the heart, the ventricle pressure is above the atrium pressure but below the aorta pressure. Which valves are open and which are closed? (2 marks)
Marking scheme: Both the atrioventricular (bicuspid) and semilunar valves are closed (1); the ventricle is contracting with a fixed volume before ejection (1).
Donat Sciences and MathsBiology · Virtual lab worksheet
School: ........................................ Name: ................................ Class: ........ Date: ............
The heart: cardiac cycle, valves and exercise
Aim: To describe the sequence of events in the cardiac cycle, to relate the opening and closing of the valves to pressure changes, and to investigate how exercise and training affect heart rate, stroke volume and cardiac output.
Apparatus (real laboratory): stopwatch, step or bench, learners’ own pulse; a sheep or goat heart for dissection.
What to do (with the simulation on www.donatstem.co.rw)
- Watch one heartbeat in slow motion. Name the stage when the atria contract and when the ventricles contract.
- Watch the valves. When are the valves between the atria and ventricles shut? When are the semilunar valves open?
- On the pressure graph, find the point where the ventricle pressure rises above the aorta pressure. What happens to the semilunar valve?
- At rest, tap Record. Then set exercise to 25 %, 50 %, 75 % and 100 %, waiting each time for a steady pulse, and record.
- Choose the athlete and repeat. Compare the graphs of cardiac output against heart rate.
- Tap Stop exercising and watch the pulse fall. Whose pulse returns to rest faster?
Results
| # | Person | Exercise (%) | Heart rate (beats/min) | Stroke volume (cm³) | Cardiac output (dm³/min) |
|---|
| 1 | | | | | |
| 2 | | | | | |
| 3 | | | | | |
| 4 | | | | | |
| 5 | | | | | |
| 6 | | | | | |
| 7 | | | | | |
| 8 | | | | | |
| 9 | | | | | |
| 10 | | | | | |
Graph
Plot cardiac output (dm³/min) against heart rate (beats/min) for both people on the same axes.
Questions
- Name the four chambers of the heart. [2]
- Why is the wall of the left ventricle thicker than the right? [2]
- What causes the "lub" and "dub" sounds? [2]
- What is the function of the valves? [2]
- Calculate the cardiac output when the heart rate is 70 beats per minute and the stroke volume is 75 cm³. [2]
- Why does an athlete have a lower resting heart rate? [2]
- Describe the events of the cardiac cycle, starting from when the atria contract. [5]
- During exercise a student’s heart rate rose from 72 to 150 beats per minute and the stroke volume from 70 to 105 cm³. Calculate the cardiac output before and during exercise and the percentage increase. [5]
- Explain why the heart rate increases during exercise. [3]
- On a pressure graph of the left side of the heart, the ventricle pressure is above the atrium pressure but below the aorta pressure. Which valves are open and which are closed? [2]
Donat Sciences and MathsBiology · Virtual lab worksheet
School: ........................................ Name: ................................ Class: ........ Date: ............
Marking scheme: The heart: cardiac cycle, valves and exercise
Expected results
Pressures (left side, mmHg) are a simplified model: ventricle 6 → 120, aorta about 80–120 with a dicrotic notch, atrium 5–11. Valves open by pressure difference: the atrioventricular valve when atrium > ventricle, the semilunar valve when ventricle ≥ aorta. Model hearts: student rests at 72 beats/min with 70 cm³ (5.0 dm³/min); athlete rests at 55 beats/min with 92 cm³ (5.1 dm³/min). Heart rate rises linearly with exercise to 195 at 100 %; stroke volume rises to its maximum (105 cm³ student, 150 cm³ athlete) by 50 % exercise. At 50 %: student about 134 beats/min, 14 dm³/min; athlete 125 beats/min, 19 dm³/min. At 100 %: 20.5 and 29.3 dm³/min. The pulse returns to rest about twice as fast for the athlete. Real learners can measure their own resting pulse, then after 2 minutes of step-ups, and every 30 s during recovery.
Answers
- Name the four chambers of the heart. [2]
Right atrium, right ventricle, left atrium and left ventricle.
- Why is the wall of the left ventricle thicker than the right? [2]
It pumps blood all around the body at high pressure; the right ventricle only pumps to the nearby lungs.
- What causes the "lub" and "dub" sounds? [2]
Lub: the valves between the atria and ventricles shutting as the ventricles contract. Dub: the semilunar valves shutting as the ventricles relax.
- What is the function of the valves? [2]
To stop blood flowing backwards, so it flows in one direction only.
- Calculate the cardiac output when the heart rate is 70 beats per minute and the stroke volume is 75 cm³. [2]
Cardiac output = 70 × 75 = 5 250 cm³ per minute ≈ 5.3 dm³/min.
- Why does an athlete have a lower resting heart rate? [2]
Training makes the heart muscle bigger and stronger, so it pumps a larger stroke volume and needs fewer beats for the same cardiac output.
- Describe the events of the cardiac cycle, starting from when the atria contract. [5]
Atria contract, pushing blood into the ventricles (1); ventricles contract and pressure rises, closing the atrioventricular valves (1); semilunar valves open and blood is pumped into the aorta and pulmonary artery (1); ventricles relax and the semilunar valves close (1); blood flows from the veins into the atria and ventricles (diastole) (1).
- During exercise a student’s heart rate rose from 72 to 150 beats per minute and the stroke volume from 70 to 105 cm³. Calculate the cardiac output before and during exercise and the percentage increase. [5]
Before: 72 × 70 = 5 040 cm³/min (1); during: 150 × 105 = 15 750 cm³/min (2); increase = (15 750 − 5 040) ÷ 5 040 × 100 (1) = 213 % (1).
- Explain why the heart rate increases during exercise. [3]
Muscles respire faster and need more oxygen and glucose (1) and must remove more carbon dioxide (1); a higher heart rate pumps more blood to them per minute (1).
- On a pressure graph of the left side of the heart, the ventricle pressure is above the atrium pressure but below the aorta pressure. Which valves are open and which are closed? [2]
Both the atrioventricular (bicuspid) and semilunar valves are closed (1); the ventricle is contracting with a fixed volume before ejection (1).