The heart as a pump Flashcards
waves on ECG
created by excitation and recovery of different regions of the heart
height reflects amount of muscle involved
P wave
atrial excitation
QRS complex
ventricular excitation
T wave
ventricular recovery
interval/segment
interval includes the peaks
segment doesn’t
isometric
contraction gives increase in tension in elastic elements first without a shortening of the muscle length
occurs if the load is too heavy to move
isotonic
when muscle tension is high enough to match the load then can move the load
muscle shortens without a further increase in tension
passive ventricular filling
pressure in ventricles falls lower than in the atria
AV (mitral and tricuspid) valves open
ventricles passively fill with blood
atrial ejection
following P wave, atria contract
another 30% blood is pushed into the ventricles
attic and pulmonary (semilunar) valves closed as pressure higher in arteries than the ventricles
isovolumic ventricular construction
following QRS ventricles start to contract
tension in muscle building (no shortening yet)
pressure higher in the ventricles than the atria
AV valves slam shut (lub)
pressure not yet high enough to open aortic and pulmonary valves
ventricular ejection
pressure in ventricles now higher than arteries
aortic and pulmonary valves open (AV valves still closed)
ejection phase
isovolumetric ventricular relaxation
following T wave ventricles start to relax
pressure falls lower in the ventricles than the arteries
aortic and pulmonary valves slam shut (dub)
ventricular pressure still higher than atria so AV valves still shut
pre-load in length tension relationship
left ventricle preload is left ventricular end-diastolic finer length
preload is the resting length from which the muscle contracts
afterload in length tension relationship
for the left ventricle is aortic pressure
Frank-starling relationship
states the volume of blood ejected by the ventricle depends on the volume present in the ventricle at the end of diastole
cardiac output= venous return