Cardiac Cycle(2) Flashcards
0
Q
What is step 2?
Ventricles about to relax
A
- Ventricles begin to relax
- IV pressure drops
- IV pressure < arterial
- Brief back flow closes outflow valves
- All valves now closed
- ISOVOLUMETRIC RELAXATION
1
Q
The cardiac cycle comprises of 10 stages starting from ventricular systole.
What is step 1?
A
- Ventricles are contracted
- IV pressure is high
- Outflow valves are open
- Blood flowing into arteries
- Ventricular pressure > atrial pressure
- AV valves are closed
2
Q
What is step 3?
Ventricles have relaxed
A
- During systole blood has continued to return to atria
- Arterial pressure still relatively high
- IV pressure decreases
- Atrail pressure > IV pressure
- a/v valves open
3
Q
What is step 4?
a/v valves have opened
A
- A/V valves are open so ventricles:
- Fill rapidly ‘rapid filling phase’
- ~200-300ms
- Most filling of ventricles occur in this phase
4
Q
What is step 5?
Ventricles are filling
A
- Diastole continues
- Ventricles fill more slowly
- IV pressure starts to increase as ventricle walls stretch
- When IV pressure = atrial pressure filling stops
- Filling of heart depends on venous pressure
5
Q
What is step 6?
About to be atrial systole
A
- Atrial systole
- Forces small extra amount of blood into ventricles
- Can pump without atrial systole
6
Q
What is step 7?
Ventricle systole
A
- Ventricular systole
- IV pressure increases v.rapidly
- Quickly > atrial pressure
- Some back flow then a/v valves close
- All valves closed
- ISOMETRIC CONTRACTION
7
Q
What is step 8?
Isometric contraction has just occurred
A
- IV pressure increases v.rapidly
- Until IV pressure > atrial pressure
- Atrial pressure has been decreasing during diastole
- Outflow vales open
8
Q
What is step 9?
Outflow valves open
A
- Outflow valves open
- Blood’s ejected rapidly into arteries
- ‘Rapid ejection phase’
- Arterial pressure increases rapidly
9
Q
What is step 10?
after rapid ejection phase
A
- As arterial pressure increases
- Rate of ejection of blood falls
- Both arterial and intraventricular pressures peak towards end of systole
- Outflow eventually ceases with blood still in ventricle
