Cardiac Cycle

Question 1

What three stages is the cardiac cycle split into?

Answer 1

• Diastole.
• Atrial systole
• Ventricular systole.

Question 2

What happens in “diastole” stage of the cardiac cycle?

Answer 2

• Atria and ventricular muscles are relaxed.
• This is when blood will enter the atria via the vena cava/ pulmonary vein.
• Blood flows into the atria, increasing the volume of blood in the atria - increasing the pressure of blood within the atria.

Question 3

What happens in “atrial systole” stage of the cardiac cycle?

Answer 3

• Atria muscular walls contract, decreasing volume of atria - increasing the pressure of blood in atria further.
• Causes atriventricular valves to open and blood to flow into the ventricles.
• The ventricular muscular walls are relaxed (ventricular diastole.)

Question 4

What happens in “ventricular systole” stage of cardiac cycle?

Answer 4

• After short delay, ventricle muscle walls contract- decreasing the volume of the ventricles, increasing the pressure of blood beyond the atria.
• Causes atriventricular valves to close and semi-lunar valves to open.
• The blood is pushed out of the ventricles into the arteries (pulmonary artery/ aorta.)

Question 5

What is the “cardiac output?” Units?

Answer 5

• Cardiac output is the volume of blood that leaves 1 ventricle in one minute.
• dm³min⁻¹

Question 6

What is the formula to calculate cardiac output?

Answer 6

Cardiac output = heart rate x stroke volume.

Question 7

What is the “heart rate?” Units?

Answer 7

• Heart rate is the number of beats of the heart per minute.
• Unit = min⁻¹

Question 8

What is the stroke volume? Units?

Answer 8

• Volume of blood that leaves the heart in each beat.
• Units: dm³

Question 9

When do atriventricular valves open/ when do atriventricular valves close?

May be asked to determine where they open/ close on graph based on pressure changes- refer to word document in “diagrams” folder.

Answer 9

• Atriventricular valves open when pressure is higher in atria compared to the ventricles.
• Atriventricular valves close when pressure is higher in ventricles compared to the atria.

Question 10

When do semi-lunar valves open/ close?

May be asked to determine where they open/ close on graph based on pressure changes - refer to word document in “diagrams” folder.

Answer 10

• Semi-lunar valves open when pressure is higher in ventricle compared to the arteries (pulmonary artery/ aorta.)
• Semi-lunar valves close when pressure is higher in the arteries compared to the ventricles.

Question 11

What happens to the volume of atria/ ventricles when their muscles contract vs relax?

Answer 11

• Contract: volume would decrease (less space in atria/ ventricles.)
• Relax: volume would increase (more space in atria/ ventricles.)

Question 12

ATRIAL SYSTOLE.

What happens to:
- Volume of atria
- Pressure in atria
- Volume of ventricles
- Pressure in ventricles.

Answer 12

IN ORDER.
- Volume decreases.
- Pressure increases.
- Volume increases.
- Decreased pressure.

Question 13

VENTRICLE SYSTOLE.

What happens to:
- Volume of atria
- Pressure in atria
- Volume of ventricles
- Pressure in ventricles.

Answer 13

• No change.
• No change.
• Large decrease
• Large increase

Question 14

DIASTOLE

What happens to:
- Volume of atria
- Pressure in atria
- Volume of ventricles
- Pressure in ventricles.

Answer 14

• Increase
• Increase in pressure - because blood starts to flow into the atria.
• Slow increase
• Slow increase.

Question 15

When we say “volume decreases”, is this referring to the blood OR the SPACE within the chamber?

Answer 15

• Space/ capacity within chamber.

Question 16

What’s the advantage of the ventricles being in diastole?

Answer 16

• Prevents backflow from arteries to ventricle.