3.2.5- The Cardiac Cycle

Question 1

What is the role of the heart?

Answer 1

To create pressure that pushed blood around the blood vessels.

Question 2

Explain what systole is.

Answer 2

The contraction phase of the cardiac cycle that results in the ejection of blood to an adjacent chamber or vessel.

Question 3

Define what diastole is.

Answer 3

Te part of the cardiac cycle where the muscles in the heart relax and the blood fills with blood again, following systole.

Question 4

What are the three main parts of the cardiac cycle, in time order.

Answer 4

diastole
Atrial systole
Ventricular systole

Question 5

Explain the first stage of the cardiac cycle, diastole.

Answer 5

The muscular walls of the four heart chambers relax and elastic recoil causes the chambers to increase in volume, creating a lower pressure so that blood flows in from the veins.

Question 6

Explain the second stage of the cardiac cycle, atrial systole.

Answer 6

Both atria contract together to create a very small increase in pressure, only small as the walls are very thin. This pushed blood into the ventricles and stretches the walls of the ventricles to ensure they’re full of blood.

Question 7

Explain the third stage of the cardiac cycle, ventricular systole.

Answer 7

Goth ventricles pump together and contraction starts at the apex (base) of the heart to ensure the blood is pushed upwards towards the arteries.

Question 8

What is the purpose of valves?

Answer 8

To ensure blood is flowing in the correct direction.

Question 9

How are valves opened and closed?

Answer 9

Changes in the blood pressure in various heart chambers.

Question 10

After systole, the ventricular walls ________ and ________.

Answer 10

Relax

Recoil

Question 11

What are the two types of valve involved in the cardiac cycle?

Answer 11

Atrio- ventricular and semilunar valves.

Question 12

Valves are attached to _________ ________.

Answer 12

Tendinous cords.

Question 13

What do the tendinous cords attached to valves do?

Answer 13

Prevent them from turning inside out.

Question 14

Where are the atrio- ventricular valves?

Answer 14

In between the atria and ventricles.

Question 15

Explain the sequence of events that explains how the Atrio- Ventricilar valves work.

Answer 15

The pressure in the ventricles drops below atria pressure after systole. Blood in atria pushes AVvalves open. Blood flows through atria to ventricles and pressure in them slowly rises. AV valves stay open whilst atria contract and close while they relax- closure caused by the swirling action in blood around the valves when ventricle’s full. As ventricles contract in systole, BP rises- when pressure rises above atria’s, blood moved upwards to fill valve pockets and keep the AV valve closed.

Question 16

What is the function of the atrio- Ventricilar valve?

Answer 16

To prevent blood flowing back into the atria.

Question 17

What is the function of the semilunar valves?

Answer 17

To prevent blood returning to the ventricles.

Question 18

Compare the pressures in major arteries and ventricles before ventricular contraction (systole).

Answer 18

The blood pressure in the arteries is higher than in the ventricles. This keeps semilunar valves closed.

Question 19

Because the pressure in arteries is higher than in the ventricles (before ventricular contraction)- it means that…

Answer 19

The semilunar valves are kept closed.

Question 20

Where are the semilunar valves found?

Answer 20

Between ventricles and major arteries.

Question 21

Explain the sequence of events that explains how the semilunar valves work to prevent blood flowing back into the ventricles after it has moved into the arteries.

Answer 21

Ventricular systole raises vent’s BP fast- SL valves pushed open when pressure’s above that of the arteries and blood forced out of ventricles in a powerful spurt. Heart muscle starts to relax in diastole after the vent’s have finished contracting. Elastic tissue in vent’s walls recoils to re stretch out the muscle, causing the pressure to drop again as its sizes increases- when it drops below major arteries’ pressure, blood flows back towards ventricles. The SL valves are pushed closed by blood collecting in the pockets of valves to prevent blood flowing back.

Question 22

Blood enters the ________ and ________ _________ in a rapid spurt.

Answer 22

Aorta

Pulmonary artery

Question 23

What is the problem created by blood flowing into the aorta and pulmonary artery in a rapid spurt?

Answer 23

The tissues require blood to be delivered in an even flow.

Question 24

Explain how the walls of arteries are adapted so that blood is delivered in an even flow.

Answer 24

The artery walls have a low of elastic tissue so when blood leaves the heart, these walls stretch. Blood moves on and out of the aorta- BP starts to drop but elastic recoil helps to maintain the pressure within the aorta the more the blood flows along the arteries, the more the pressure drops and the fluctuations become less obvious.

Question 25

Explain why it is important to maintain the pressure gradient between the arterioles and the aorta

Answer 25

The pressure gradient is what keeps the blood flowing towards the tissues.

Question 26

Define what the cardiac cycle is.

Answer 26

The coordinated sequence of events within one full beat of the heart.