Cardiac Cycle and Cardiac Output Flashcards
repetitive sequence of events with each heart beat
- flow into atria, continuous except when they contract. inflow leads to pressure rise
- opening of AV valves - flow to ventricles
- atrial systole - completes filling of ventricles
- ventricular systole (atrial diastole) - pressure rise closes AV valves, opens aortic and pulmonary valves
- ventricular diastole - causes closure of aortic and pulmonary valves
1st heart sound
closing of AV valves
2nd heart sound
closing of semilunar valves
3rd heart sound
early diastole of young and trained athletes
normally absent after middle age
termes ventricular gallop
re-emergence in later life indicates abnormality
4th heart sound
caused by turbulent blood flow
due to stiffening of walls of left ventricle
occurs prior to 1st sound
atrial gallop
do the chambers of the heart empty completely
no
what helps maintain pressure in arterial system during diastole
elastic arterial tree
stroke volume
volume of blood pumped by each ventricle per beat
may double during exercise
ejection fraction
% volume pumped out
normally 55-60%
exercise 80%
heart failure 20%
systemic arterial pressure
remains high throughout cycle due to elasticity of vessel walls and peripheral resistance
cardiac output
volume of blood pumped per minute by each ventricle
CO = HR x SV
effect of HR on cardiac output
normally increased HR is associated with increased CO
if decreased filling time then decreased SV
** venous return determines cardiac output
what is stroke volume dependent on
contractility
end diastolic volume
contractility
the force of contraction
e.g. adrenaline increases force which increases SV
end diastolic volume
the volume of blood in ventricle at the end of diastole
force is stronger the more muscle fibres are stretched
frank-starling mechanism or starlings law of the hearr
SV ∝ diastolic filling
