Cardiac Cycle

Question 1

What are the two phases of the cardiac cycle? (2)

Answer 1

1) Filling phase - Blood enters
Atria -> AV valves -> Ventricles

2)Emptying phase - Blood leaves
Semi-linar valves -> Aorta / pulmonary artery

Question 2

What are the 4 proper phases of the cardiac cycle? (involving valves)

Answer 2

1) Inflow phase - Av open, semi-lunar closed
2) Isovolumetric contraction - Both closed
3) Outflow phase - Av closed, semi-lunar open
4) Isovolumetric relaxation - both closed, no blood flow

Isovolumetric - with no volume change

Question 3

What is a Diastole and Systole?

Answer 3

Diastole – ventricles relaxing
Systole – ventricles contracting

Question 4

Are the 4 phases of the cardiac cycle a diastole or systole?

Answer 4

1) Inflow phase - Diastole
2) Isovolumetric contraction - Systole
3) Outflow phase - Systole
4) Isovolumetric relaxation - Diastole

Question 5

Describe end phase 1 in the cardiac cycle? (8)

Answer 5

-Mitral valve open
-Little flow A to V
-V volume increases slowly
-A pressure just above V pressure

-Atrial contraction
-20% SV equivalent enters V
-Small increase in V volume
-Increase pressure A and V

Question 6

Describe end Phase 2 (isovol contract) in the cardiac cycle? (6)

Answer 6

-Start systole
-V contract - increases pressure
-Vpressure > Apressure
-Mitral valve closes

-Vpressure eventually > Aortapressure
- opens semi-lumar valve (end of phase 2)

Question 7

Describe end Phase 3 (outflow) in the cardiac cycle? (6)

Answer 7

-Rapid ejection – Vpressure still increases & V volume falls
-Blood moves into aorta – AOpressure increases

-AOpressure increases > Vpressure

-Both pressures drop a little

~70 ml leaves
~50ml remains

-Note rise in Apressure

Question 8

Describe end Phase 4 (isovol relax) in the cardiac cycle? (6)

Answer 8

-Blood flow across semi-lunar valve stops & reverses – valve closes

-Onset diastole
-Vpressure falls rapidly

-Both valves closed – isolvolumetric relaxation – no blood can enter the ventricles

Question 9

Describe early phase 1 (inflow)? (4)

Answer 9

-Vpressure < Apressure
-Mitral valve opens

-Ventricular volume increases
-V and A pressures increases

Question 10

What are the normal cardiac volumes?

Answer 10

Cardiac Output (CO) = HR x SV ~5L/min (rest)

Stroke Volume (SV) = volume blood ejected per heartbeat, ~70ml (rest) EDV-ESV

End-diastolic volume (EDV) ~120ml
End systolic volume (ESV) ~50mls

Ejection fraction = SV/EDV

Healthy should be at least 0.55