Cardiovascular mechanics 2 Flashcards
What are the two main phases of the heart beat
Systole and Diastole
What are the approximate time lengths of each phase
diastole = 2/3 of each beat Systole = 1/3 of each beat
How many phases is diastole split into
4
How many phases is systole split into
3
What are the three stages of systole
Isovolumetric contraction
Rapid ejection
Slow ejection
What occurs during isovolumetric contraction
Interval between the AV valves closing and the semi-lunar valves opening.
Isometric contraction of the ventricles
What occurs during rapid ejection
Aortic and pulmonary valves open
Ventricles contract. Pressure exceeds that in the aorta and the semilunar valves open and blood is pumped out
What occurs during slow ejection
Reduced pressure gradient as the semilunar valves begin to close
Blood flow from the ventricles decreases and volume decreases slowly
Semilunar valves close
Describe a typical ECG trace
P - atrial systole
QRS complex - ventricular depolarisation
What are the 4 phases of diastole
isovolumetric relaxation
Rapid passive filling
Slow passive filling
Atrial systole
Which diastolic phase is the longest
Slow passive filling
What occurs during isovolumetric relaxation
Semilunar valves shut. Atrial pressure continues to increase, isometric relaxation of the ventricles (volume does not change)
What occurs during rapid passive filling
The AV valves open and blood form the atria flow rapidly into the ventricle
What occurs during slow passive filling
Ventricular volume fills more slowly but considerably
What occurs during atrial systole
Atria are full from passive filling (pressure gradient) and the atria contract to top up the ventricular blood volume
Explain the ‘Lub dub’ sound of the heart
Lub is from the atrioventricular valves closing (isovolumetric contraction)
Dub is from the semi-lunar valves closing (isovolumetric relaxation)