L03: Cardiac Cycle

Question 1

What is the equation for atrial blood pressure

Answer 1

Stoke volume x heart rate x total peripheral resistance

Question 2

What activity does the electrical activity of the heart stimulate

Answer 2

Mechanical activity

Question 3

What does mechanical activity cause

Answer 3

Pressure and volume change

Question 4

What is the cardiac cycle

Answer 4

The coordinated series of pressure and volume changes in the heart

Question 5

What does the cardiac cycle result in

Answer 5

Ejection of a volume of blood from the ventricles

Question 6

What is the ejection of blood form the ventricles known as

Answer 6

Stroke volume

Question 7

Which 2 clinical cases can affect the cardiac cycle

Answer 7

Myocardial infarction

Valve defect

Question 8

What happens to the cardiac cycle length when the heart rate increases

Answer 8

Decreases

Question 9

What are the 2 phases of the cardiac cycle

Answer 9

Diastole

Systole

Question 10

Which stage occupies the most of the cardiac cycle

Answer 10

Diastole

Question 11

What are the 5 principles of the cardiac cycle

Answer 11

• Contraction of the muscles around chamber increase the pressure
• Valves open when there is a pressure energy gradient across them (greater in atrium than ventricles)
• blood flows down a pressure gradient
• when valves open pressure in neighbouring chamber change
• when valves close pressure in neighbouring valves can be different

Question 12

Is the pattern of the pressure change same on both sides of the heart (right and left side)

Answer 12

Yes

Question 13

Do valves on the right and left side of the heart open and close at the same time in the same way ?

Answer 13

Yes

Question 14

What are the phases of the cardiac cycle

Answer 14

1) ventricular diastole: rapid filling
2) ventricular diastole, atrial systole and ventricular filling
3) ventricular systole: isovolumetric contraction
4) ventricular systole : ejection
5) ventricular diastole: isovolumetric relaxation

And this goes back to first step of the ventricular diastole: rapid filling to repeat the cardiac cycle

Question 15

Top tip for remembering the phases of the cardiac cycle

Answer 15

The phase of the cardiac cycle mostly refers to the ventricles and their state e.g ventricular diastole and ventricular systole

Question 16

What are the valves present in the left heart

Answer 16

Mitral valve

Aortic valve

Question 17

What are the valves called in the right heart

Answer 17

Tricuspid valve

Pulmonary valve

Question 18

In terms of the left side of the heart what happens at the phase of ventricular diastole (rapid filling)

Answer 18

1) pulmonary vein has greater pressure than the atrial pressure
2) mitral valve is open because the atrial pressure is greater than the ventricular pressure
3) ventricles fill with blood
4) aortic valve is closed because the ventricular pressure is lower than the aortic pressure

Question 19

Describe what happens at the ventricular diastole, atrial systole, ventricular filling phase

Answer 19

1) atrial depolarisation leads to atrial contraction so there is an increase in atrial pressure
2) increase in atrial pressure leads to blood flowing into ventricles (ventricles are at rest)

Question 20

Describe what happens at the ventricular systole, isovolumetric contraction phase

Answer 20

1) the ventricles contact so ventricular pressure increase
2) as ventricular walls are thick there is a greater increase in pressure in the ventricles
3) ventricular pressure is greater than the atrial pressure so mitral valves close
4) ventricular pressure is still smaller than the aortic pressure so aortic valve is also closed
5) as both valves are closed volume of blood remaining in the ventricles is the same = isovolumetric contraction
6) continuing ventricular contraction causes the pressure to increase in ventricles which is greater than the aortic pressure
7) blood ejects out into the aorta
8) aortic pressure is greater than the ventricular pressure as ejection continues

Question 21

Describe what happens in the ventricular diastole, isovolumetric relaxation

Answer 21

1) ventricle repolarisation occurs so the ventricles relax and ventricular pressure decreases
2) aortic valve closes as ventricle pressure is smaller than aortic pressure
3) ventricular pressure is greater than the atrial pressure so mitral valve closes
4) both valves are closed so volume of blood in the ventricles remain the same= isovolumetric relaxation

Question 22

What does the lub sound of the heart represent

Answer 22

Mitral valve and tricuspid valve close

Question 23

What does the dub sound of the heart represent

Answer 23

Pulmonary and aortic valve close

Question 24

Why does the atrial pressure change slight during contraction

Answer 24

Atrial wall muscles are thin

Question 25

Which side of the heart has a lower pressure

Answer 25

Right side

Question 26

Why does the right side of the heart have a general lower pressure

Answer 26

Pulmonary resistance is lower so a lower pressure is required to overcome the smaller resistance

Question 27

Why does the left side of the heart have a higher pressure

Answer 27

Systemic resistance is high so the left side needs a higher pressure to overcome the higher pressure to drive blood flow out.