the heart as a pump Flashcards
does systemic circulation or pulmonary circulation occur at higher pressure and which side of the heart does each?
systemic occurs at a higher pressure as it is to the rest of the body and is conducted by the left side as a result myocardium is thicker on the left. whereas pulmonary circulation is to the lungs by the right side.
what does the pulmonary vein do?
brings oxygenated blood to the heart
where does blood that enters the superior vena cava and inferior vena cava come from
deoxygenated blood from the top of the body enters the superior vena cava and deoxygenated blood from the lower part of the body enters via the inferior vena cava
how much blood does each ventricle pump any rest
70ml
what causes cardiac cells to contract and what does this cause a rise in
cardiac cells contract in response to action potentials.
action potentials cause a rise in intracellular calcium
how do c cardiac cells communicate with each other
via gap junctions allowing unimpeded signal ( action potential)
what is different about the mitral valve compared to the others
it only has two leaflets whereas the other valves have three leaflets
what muscles are the cusps of mitral and tricuspid valves attached to and how are they attached
to papillary muscles via chordae tendineae
which cells generate an action potential and where are they found
pacemaker cells in sinoatrial node generate an action potential. This is where the signal originates
what happens to signal created in sinoatrial node
it spreads over the atria during atrial systole.
when it reaches the atrioventricular node it is delayed for 120 seconds allowing the atria to finish contracting. the excitation now spreads down the septum between ventricles.
next it spreads through ventricular myocardium from inner (endocardial) to outer (epicardial) surface.
ventricle contracts from the apex up forcing blood through outflow valves
what are the 7 phases of the cardiac cycle
1) atrial contraction
2) isovolumetric contraction
3) rapid ejection
4) reduced ejection
5) isovolumetric relaxation
6) rapid filling
7) reduced filling
when heart rate increases how does this affect diastole time and systole time?
systole time stays the same and diastole time decreases
what does a p wave in an egg represent
depolarisation of atria
what does the QRS complex in an ECG represent
depolarisation of ventricles
what does the t wave in an ECG represent
ventricular repolarisation
what occurs in phase 1 of cardiac cycle
atrial contraction
‘A wave’ on ECG as atrial pressure increases
atrial kick- atria contracting only accounts for final 10% of blood filling ventricles. the rest fills passively as the valves open
mitral/ tricuspid valve open but aortic/pulmonary valve closed
what occurs in phase 2 of cardiac cycle
isovolumetric contraction
mitral valve closes as intraventricular pressure exceeds atrial pressure. this causes ‘c wave’ in atrial pressure curve( as the valve closes it bulges back into the atria)
closure of mitral and tricuspid valve causes first heart sound(lub) known as S1.
what occurs in phase 3 of cardiac cycle
rapid ejection
begins when intraventriclaur pressure exceeds pressure in aorta causing aortic valve to open.rapid decrease in ventricular volume as blood is ejected into aorta.
‘X descent’ is present in the atrial pressure curve as when the ventricles contract the atrial base is pulled down decreasing the pressure.
what occurs in phase 4 of cardiac cycle
reduced ejection
repolarization of ventricle(t wave) leads to a decrease in tension and the rate of ejection begins to fall.
‘v wave’ in atrial pressure curve as atrial pressure increases due to the continued venous return from the lungs.
what occurs in phase 5 of cardiac cycle
isovolumetric relaxation
intraventricular pressure falls below aortic pressure so there’s a brief back flow of blood causing the aortic valve to shut (seen as discrotic notch in aortic pressure curve)
closure of aortic and pulmonary valves results in the second heart sound (dub-s2)
what occurs in phase 6 of cardiac cycle
rapid filling
intraventricular pressure is lower than atrial pressure causing mitral valve to open. this causes a fall in atrial pressure which is seen as the ‘y-descent’ on atrial pressure curve
what is s3
ventricular filling is normally silent but sometimes a third heart sound can be present. this is normal in children but a sign of pathology in adults
what occurs in phase 7 of cardiac cycle
reduced filling( diastasis-middle stage of diastole) as ventricles reach its inherent relaxed vol.
what is stenosis
valve doesn’t open enough obstructing blood flow.
what is regurgitation
valve doesn’t close enough causing back leakage
what are the causes of aortic valve stenosis
degenerative- senile calcification/fibrosis
congenital- bicuspid form of valve
autoimmune-chronic rheumatic fever,inflammation
what happens in aortic valve stenosis
increased LV pressure causing LV hypertrophy
left sided heart failure causing syncope (fainting) or angina
what causes aortic valve regurgitation
aortic root dilation (leaflets pull apart)
valvular damage
what happens in aortic valve regurgitation
systolic pressure increases
diastolic pressure decreases
bounding pulse(head bobbing, quinke’s sign which is when the nail bed flushes red and pale for each beat of the heart)
LV hypertrophy
what is mitral valve prolapse and how is it prevented
it is the bulging of one or both of the mitral valve flaps (leaflets) into the left atrium.
prevented by papillary muscle and chordae tendineae
why can mitral valve regurgitation cause LV hypertrophy
as some blood leaks back into LA increasing preload as more blood enters LV in subsequent cycles.
what causes mitral valve stenosis
rheumatic fever
what can happen in mitral valve stenosis
increased LA pressure causes the following :
pulmonary oedema
dyspnea- difficulty in breathing
the above 3 cause RV hypertrophy
enlargement of LA causes oesophagus compression and atrial fibrillation(which is irregular heart rhythm, this can eventually lead to clots in heart )
