Cardiac Cycle Flashcards
What are capacitance vessels?
Enable system to vary amount of blood pumped around the body
What are resistance vessels?
Restrict blood flow to drive supply to hard to perfuse areas of the body
What is systole?
Contraction and ejection of blood from ventricles
What is diastole?
Relaxation and filling of ventricles
What is stroke volume?
Amount of blood pumped out of the heart in one beat
~70ml
What are the phases of the cardiac cycle?
- atrial contraction
- isovolumetric contraction
- rapid ejection
- reduced ejection
- isovolumetric relaxation
- rapid filling
- reduced filling
What phases are in diastole?
- isovolumetric relaxation
- rapid filling
- reduced filling
- atrial contraction
What phases are in systole?
- isovolumetric contraction
- rapid ejection
- reduced ejection
What happens when heart rate increases?
Systole length stays the same
Diastole gets shorter
What is Wiggers diagram?
Google picture
draw out
- atrial contraction
A wave - atrial pressure rises due to atrial systole
Atrial contraction ~10% of ventricular filling
- isovolumetric contraction
Mitral valve closes - c wave
Ventricle contracts - rise in ventricular pressure
No change in ventricular volume
- rapid ejection
Aortic valve opens
- because intraventricular pressure > aortic pressure
x-descent - atrial pressure decreases - atrial base pulled down
Decrease in ventricular volume
- reduced ejection
Repolarisation of ventricle - decline in tension - ventricular pressure drops
V wave - atrial pressure rises due to venous return from lungs
- isovolumetric relaxation
Aortic valve closes
- intraventricular pressure < aortic pressure
Dicrotic notch - aortic pressure increases slightly as valve closes
Rapid decline in ventricular pressure
Ventricular volume remains constant
