Cardiovascular system Flashcards
What happens in the diastolic phase?
relaxation of myocardium
What happens in the systolic phase?
Contraction of myocardium
What is tachycardia?
resting heart rate above 100bpm
what is bradycardia?
heart rate below 60bpm
what is premature atrial contraction?
occasional shortened intervals between contractions
Cardiac output
The amount of blood the heart pumps through the circulatory system in a minute.
CO = Heart rate x Stroke vol
Stroke volume
volume of blood pumped by a ventricle per beat
SV = End diastolic vol (EDV) - End systolic vol (ESC)
ejection fraction
% of EDV pumped by ventricle
what happens during ventricular filling?
ventricular diastole (relax)
atrial systole (contract)
isovolumetric contraction
ventricles contract (systole)
AV valve closed
ventricular ejection
ventricles contract (systole)
isovolumetric relaxation
ventricles and atria relax (diastole)
what does the impulse conductor do?
ensures atria and ventricles contract separately
What is preload?
tension/stetching before muscle works
EDV
what is afterload?
pressure that preloaded muscle has to work against
what effect does increase in preload have on cardiac output?
increases CO
what happens to cardiac output when afterload is increased?
CO decreases
3 steps of the renin-angiotensin-aldosterone system?
1) renin secreted by kidneys when BP is reduced
2) converts angiotensinogen to angiotensin I
3) ACE converts angiotensin I to II
Actions of angiotensin II?
vasoconstriction
causes release of aldosterone
increase blood volume and pressure
function of ACE inhibitors?
inhibit angiotensin formation
decrease aldosterone
what happens at the SA node?
generates spontaneous action potentials
what happens at AV node?
Action potentials conducted slowly
ensures that ventricles contract after atria
Function of purkinje fibres?
conduct action potentials to ventricle muscles (myocardium)
heart attack
deprivation of supply of blood to tissue
cardiac arrest
disruption to control of contractions
heart failure
inability to distribute blood around body