Cardiac cycle : pressure & volumes

Question 1

what are the 4 chambers of the heart?

Answer 1

Question 2

What are the** 4 valves **of the heart?

Answer 2

1. Atrioventricular valve
2. **Biscupid **valve (also called mitral valve)
3. Triscupid valve
4. Semilunar valve/ pulmonary valve
5. **Aortic **valve

Question 3

What does the atrioventricular valve seperate?

Answer 3

• seperates the atria from the ventricles
• so, note if pressure is higher in the atria than the ventricles, then blood flows from A-V (high pressure - low pressure)

Question 4

What does the bicuspid valve seperate?

Answer 4

• on the LEFT SIDE
• seperates the left atrium from the left ventricle

Question 5

What does the tricuspid valve seperate?

Answer 5

• on the RIGHT side
• seperates the **right atrium from the right ventricle **

Question 6

What dooes the semilunar/pulmonary valve seperate?

Answer 6

• seperates the right ventricle from the pulmonary artery

Question 7

What does the aortic valve seperate?

Answer 7

• seperates the left ventricle from the aorta

Question 8

what is the cardiac cycle defined as?

Answer 8

the repeated pattern of cardiac contraction & relaxation

Question 9

What is cardiac contraction defined as?

Answer 9

• systole
• pushes the blood out of the heart into vasculature

Question 10

what is cardiac relaxation defined as?

Answer 10

• diastole
• allows the heart to fill with blood

Question 11

What are the 2 phases of diastole called?

Answer 11

1. Passive filling
2. Atrial contraction

Question 12

What does the passive filling phase involve?

Answer 12

• the **atria and ventricles are relaxed **
• the ventricles are** passively filled with blood**
• AV valves are open, Semi lunar valves are closed

Question 13

What does atrial contraction involve?

Answer 13

• happens at the end of diastole
• 80% of blood has already filled the ventricles- note this action increases the EDV ventricular volume by 25%
• the** atria contract** and** fill the ventricles fully**
• AV valves open, SL valves closed

Question 14

What is the** volume of blood** that fills the ventricle just before it contracts called?

Answer 14

• The end - diastolic volume (EDV)

Question 15

What happens after the atrial contraction phase?

Answer 15

• the** pressure in the atria begins to fall**, this causes the closing of the AV valves (to prevent backflow from ventricles to atria)
• this produces the S1 sound and marks the beginning of the systole

Question 16

What forms the S1 sound (‘lub’)

Answer 16

• closing of the AV valves after atrial contraction

Question 17

What are the 3 phases of systole?

Answer 17

1. Isovolumetric contraction
2. ventricular ejection
3. **Isovolumetric **relaxation

Question 18

Describe the isovolumetric contraction phase

Answer 18

• AV valves closed
• semi lunar valves are closed for a moment
• the ventricle is full of blood and begins to** contract,** but as the valves are all closed, no blood is ejected from the ventricles
• no change in volume

Question 19

Describe the ventricular ejection phase

Answer 19

• ventricle contracts further
  * semilunar valve opens
• the contraction increases the pressure in the ventricle
• aortic valve opens
• this increase in pressure allows blood to be ejected from the ventricles to the aorta/pulmonary artery to systemic / pulmonary circulation

Question 20

Describe the isovolumetric relaxation

Answer 20

• the semi lunar valves close
• the AV valves are still closed
• no change in volume
• back to diastole after this phase

Question 21

What is the volume of blood called after the ventricular contraction?

Answer 21

• the end- systolic volume (ESV)

Question 22

What causes the S2 sound?

Answer 22

• the semilunar valves closing after ventricular contraction

Question 23

How is the stroke volume related to the end diastolic volume & the end systolic volume?

Answer 23

• the stroke volume is the difference between the EDV and the ESV

Question 24

How do ventricular pressures change during the cardiac cycle?

Answer 24

* pressure is low in the first phase of diastole (passive filling), as the AV valves are open and blood is flowing in
* there is a** slight rise in pressure** in the 2nd phase (atrial contraction) as the volume of blood is increasing in the ventricles
* during the 1st phase of systole (isovolumetric contraction), there is a huge rise in pressure, as the ventricle begins to contract but no blood is ejected
* during the 2nd phase of systole (ventricular ejection), pressure still increases as the ventricle is contracting lots
* after ventricular ejection, the pressure falls in the ventricle

Question 25

Why is the left systolic ventricle pressure higher than the right systolic ventricle pressure?

Answer 25

• this is due to a larger and thicker left side of the heart
• the left ventrile has to **eject blood against a higher arterial pressure **than the right ventricle, even though they both pump the same amount of blood

Question 26

What are the main components in the atrial pressure waveform?

Answer 26

1. a wave
2. c wave
3. x descent
4. v wave
5. y descent

Question 27

What is the a wave in the pressure waveform of the heart?

Answer 27

• this wave represents the contraction of the right atrium, while the tricuspid valve is open.

Question 28

What is the C wave?

Answer 28

• this wave appears at the hump of the base of the a wave
• it reflects the bulging of the tricuspid valve into the** right atrium** during ventricular systole & the pressure of the carotid pulse on the jugular vein (in neck)

Question 29

What is the x descent?

Answer 29

• reflects the relaxation and initial rapid filling of the right atrium while the tricuspid valve remains closed

Question 30

What is the v wave?

Answer 30

• right atrial filling

Question 31

What is the y descent?

Answer 31

• right atrial emptying into the right ventricle