Topic 1: Cardiac cycle

Question 1

Key Definition
(Cardiac cycle) Give the definition.
(3 points)

Answer 1

1. The cardiac cycle is the sequence of events from one heartbeat to the next heartbeat,
2. involving relaxation (heart fills with blood)
3. and contraction (heart empties).

Question 2

During the cardiac cycle, both sides of the heart are ___________ ( they contract and relax at the same time).

Answer 2

synchronised

Question 3

Each time the heart beats (one cardiac cycle takes place), blood gets pushed out of the heart to the ______ and _____.

The _______ and _______ inside the chambers of heart change as they contract and relax.

CONTRACTION (systole) __________ the volume and _________ the pressure in the chamber

RELAXATION (diastole) ________ the volume and ________ the pressure in the chamber

Answer 3

lungs body

volume pressure

decreases increases

increases decreases

Question 4

What are the stages of the cardiac cycle?

3 stages

Answer 4

1. Atrial systole
2. Ventricular systole
3. Diastole

Question 5

Explain diastole
(5 points)

Answer 5

1. Both atria and ventricles are RELAXING
2. Elastic recoil of the walls of the atria and ventricles causes heart volume to INCREASE and pressure in the heart to DECREASE
3. decrease in pressure in ventricles CLOSES THE SEMILUNAR VALVES
4. The ATRIA FILL WITH BLOOD from the vena cava and pulmonary vein
5. Blood flows PASSIVELY from atria into the relaxing ventricles, as the ATRIOVENTRICULAR VALVES ARE OPEN

Question 6

Explain atrial systole

4 points

Answer 6

1. Both atria CONTRACT (ventricles are relaxing)
2. Pressure in the atria INCREASES, pushing the ATRIOVENTRICULAR VALVES MORE FULLY OPEN
3. Blood is FORCED through the atrioventricular valves into the ventricles (atria empty)
4. Ventricles FILL with blood (volume increases)

Question 7

Explain ventricular systole

6 points

Answer 7

1. Both ventricles CONTRACT from apex upwards (while atria are relaxing)
2. as the atria are now relaxing, there is a higher pressure in the ventricles than in the atria
3. pressure difference causes the ATRIOVENTRICULAR VALVES TO CLOSE (so no blood can flow back into atria)
4. semilunar valves are still closed (short time when all 4 valves are closed)
5. PRESSURE IN THE VENTRICLES INCREASES
6. a higher pressure in the ventricles than in arteries causes the SEMILUNAR VALVES TO OPEN and blood is forced into the aorta and pulmonary artery

Question 8

Label the cardiac cycle pressure graph (using flashcard)

AV valves close

next cardiac cycle starts

SL valves open

SL valves close

Pressure increases due to ventricular systole

Pressure increases due to atrial systole

Cardiac diastole

Pressure decreases as ventricles start to relax

AV valves open

Answer 8

1. Pressure increases due to atrial systole
2. AV valves close
3. Pressure increases due to ventricular systole
4. SL valves open
5. Pressure decreases as ventricles start to relax
6. SL valves close
7. AV valves open
8. Cardiac diastole
9. Next cardiac cycle begins

Question 9

How do you work out heart rate from cardiac cycle pressure graph?
(2 steps)

Answer 9

1. Work out time between the same points on two consecutive cycles (time for one cardiac cycle)
2. 60 seconds / time for one cardiac cycle = ? bmp