Lecture 12- Cardiac Cycle Flashcards
What does cardiac cycle consist of?
series of mechanical events, pressure and volume changes, in the heart during one heartbeat.
Systole
contractile phase of the cardiac cycle.
Diastole
relaxation phase of the cardiac cycle.
When does ventricular filling occur?
during mid-to-late ventricular diastole, when the atrioventricular valves are open, semilunar valves are closed, and blood is flowing passively into the ventricles
End distolic volume
volume of blood in each ventricle at the end of ventricular diastole.
What happens during Ventricular systole?
atria relax and the ventricles contract
End systolic volume
volume remaining in each ventricle after systole.
When does isovolumetric relaxation occur?
during early diastole, resulting in a drop in ventricular pressure, which then causes closure of the semilunar valves before the opening of the atrioventricular valves.
Dicrotic notch
Brief rise in blood pressure due to back flow in aorta and pulmonary trunk
What does the first heart sound “lub” correspond to?
The closure of the atrioventricular valves during ventricular systole
What does the second heart sound “dub” correspond to?
Closure of the aortic and pulmonary valves during ventricular diastole
Heart murmurs
Extraneous hart sounds due to turbulent back flow of blood through a valve that does not fully close (incompetent valve) or does not fully open (stenotic valve)
S1 heart sound
Sound of the tricuspid and bicuspid atrioventricular valves closing at the start of ventricular systole
S2 heart sound
Sound of pulmonary and aortic semilunar valves closing at the beginning of the ventricular diastole
Cardiac output
Defines as the amount of blood pumped out of a ventricle per minute
Calculate as the product of stroke volume and heart rate
Stroke volume
Amount of blood pumped out of the heart during one cardiac cycle
Cardiac reserve
Difference between the resting and maximal cardiac output
End diastolic volume (EDV)
Amount of blood that collects in the ventricles during diastole
End systolic volume (ESV)
Volume of blood that remains in the ventricle after contraction is complete
How to calculate normal stroke volume
end diastolic volume - end systolic volume
Frank starling law of heart
States that the critical factor controlling stroke volume is preload
Preload
degree of stretch of cardiac muscle cells immediately before they contract.
Contractilitiy
Contractile strength of a muscle
After load
Ventricular pressure that must be overcome before blood can be ejected from the heart and doe snot become a significant factor for stroke volume except in hyper extensive individuals
What does sympathetic stimulation of pacemaker cells do?
increases heart rate and contractility by increasing Ca2+ movement into the cell.
What dos parasympathetic inhibition of cardiac pacemaker cells do?
decreases heart rate by increasing membrane permeability to K+, hyperpolarizing the cells.
When does Congestive heart failure occur?
when the pumping efficiency of the heart is so low that blood circulation cannot meet tissue needs.
