PHYSIOLOGY - Cardiac Cycle Flashcards
What % of total ventricular volume flows into ventricles before atrial contraction?
Between 80-100%
What % of ventricular volume is pushed into ventricles by atrial contraction?
Up to 20%
What is diastesis?
Slow filling of ventricles - before atrial contraction
Under a slow heart rate, ventricular filling is complete at diastesis t/f?
True
What is tachycardia?
Increased heart rate
What happens to ventricular filling during tachycardia?
- diastesis is shortened
- contributions of atrial contraction to ventricular filling is increased
What is syncope?
Fainting
What can happen if inadequate ventricular filling occurs?
Fainting/syncope
What happens to significance of atrial contraction during intense exercise and why?
-atrial contraction becomes more significant
- because ventricular contraction can occur during rapid filling stage
In the atrial pressure curve, what does the A wave indicate?
The rise in pressure caused by atrial contraction
In the atrial pressure curve, what does the C wave indicate?
The increase in pressure in the atrium due to AV valves bulging into atria during ventricular systole
In the atrial pressure curve, what causes the V wave?
The rise in pressure associated with atrial filling
When does rapid filling of ventricles occur and what causes it?
- occurs during ventricular diastole
- Atrial pressure > Ventricular pressure since blood has been filling up the atria
During the A wave, what does the pressure increase by in the left atrium?
7-8mmHg
During the A wave what does atrial pressure increase by in the right atrium
4-6mmHg
What causes the venous pulse?
- there are no valves at the junction of the veins and atria
- pressure changes in atria are transmitted back to large veins
What is a significant venous pulse in the body?
Jugular venous pulse
What are the 3 waves of the venous pulse curve and what causes them?
A, C, V waves
- A by atrial contraction
- C by ventricular contraction
- V by volume in atria increasing
What is atrial fibrillation?
An arrythmia which causes uncoordinated contractions of atrial fibres.
What is absent from the ECG in atrial fibrillation?
The P wave
What are the irregular fluctuations on the ECG during atrial fibrillation called?
F waves
What is the range of time of the interval between ventricular contractions?
Between 0.35 and 0.95 seconds
What is the normal amount of time for the interval between ventricular contractions?
0.8 seconds
Why is atrial fibrillation not life threatening, in theory?
- ventricular filling is normally almost complete during diastesis.
- normal stroke volume, despite atrial contraction not occurring
- electrical impulse can still be propagated in ventricles through AV node, provided it is the atrial fibres that are damaged and not the SA node