L13 - The Cardiac Cycle

Question 1

What is the cardiac cycle?

Answer 1

The sequence of mechanical and electrical events that repeat with each heart beat.

Question 2

What are the 4 phases of the cardiac cycle?

Answer 2

Inflow phase, isovolumetric contraction, outflow phase, isovolumetric relaxation.

Question 3

What does isovolumetric mean?

Answer 3

No volume change

Question 4

Phase 1 - Inflow phase

Answer 4

Diastole - Atrial contraction
- Atrioventricular/Mitral valve open.
- Volume increases slowly and atrial
pressure is just above ventricular
pressure.
- Semi-lunar valve closed.

Question 5

Phase 2 - Isovolumetric Contraction

Answer 5

Start of Systole - Ventricular Conraction
- Ventricals increase in pressure.
- Ventricular pressure rises above atrial
pressure
- Both vales closed.

Question 6

Phase 3 - Outflow phase

Answer 6

Systole
- Rapid ejection, ventrical volume falls as
blood moves into the aorta.
- Pressure of the atria and ventricals drop a
bit.
- Atriovenricular valves closed, semi-lunar
valves open.

Question 7

Phase 4 - Isovolumetric relaxtation

Answer 7

Diastole
- Blood flow across the semi-lunar values
stops & reverses
- Ventricular pressure falls rapidly.
- Both valves closed, no blood flow into the
ventricles.

Question 8

What does the P wave Mean on an ECG?

Answer 8

Depolarisation of atrial myocytes (Atrial contraction)

Question 9

What does the QRS wave mean on an ECG?

Answer 9

Ventricular myocyte deploarisation (Ventricular Contraction)