Cardiac Cycle Flashcards
What are the two main phases of heart beat
Diastole 2/3 - ventricular relaxation - 4 subpahses
Systole 1/3 - ventricular contractions - 3 subphases
End
Maximum volume of blood in heart just before ventricle contraction
Maximum relaxation
Maximum filling in heart
End systolic volume
Amount of blood in heart after contraction completed
Atrial systole
P wave on ECG
Atria almost full but atria contraction tops up the volume of blood in ventricle - 10% to 40% filling
4th heart sound - congestive heart failure - valva incompetence - pulmonary embolism - abnormal
Isovolumetric vonctraction
QRS compelx marks start of ventricular depolarisation
Interval between AV valces closing and semi-lunar valves opening
No change in volume
Ventricular pressure increases till it becomes close to aortic pressure
1st heart sound lub due to closure of AV valves
Rapid ejection
Intraventricular pressure exceed pulmonary artery and aorta
End of systole
Opening of aortic and pulmonary valves
Ventricular volume begeins to fall
No heart sounds
Reduced ejection
End of systole
Ventricular muscle cells repolarisation
Aortic and pulmonary valves begin to close
Ventricular voluem decreases more slowly
Blood flows back causing semilunar valves to close
Produces T wave
Isovolumetric relaxation
AV valves remain closed until ventricular pressure drops below atrial pressure
Rate of pressure decline in ventricles is determined by rate of relaxation of muscle fibres - lusitropy - regulated by calcium ATPase in SR membrane
Atrial pressure continues to rise
Dichoritc notch caused by rebound pressure against aortic valve as distended aortic wall relaxes
2nd heart sound dub
Rapid passing filling
Ventricular pressure fall below atrial pressure
AV valves rapidly open
No eletrical activity
3rd heart sound - abnormal - turbulent ventricular filling - incompetent valve dont shut properly
Reduced psasive filling
Also called diastasis
Ventricular voluen fill smore slowly
Ventricles are able to fill considerably without contraction
How much does the right ventricle pump in comparison to the left
Same volume of blood
What does the pulmonary capillary wedge pressure give us an indication of
Left atrial pressure
severeity of left ventricular failure and mitral valve stenosis
Pulmonary circuit pressures
When do you encounter afterload
Just after isovolumetric contraction
Blood pressure in aorta and pulmonary aorta is afterload
What is contractility of the heart
Contractile capability of the heart
Increased by: sympathetic stimulation
Extrsinici mechanism: change Ca delivery
PV loop during exercise
Large sympathetic acitvation overcomes the increase in afterload
