Session 2- The heart as a pump and valve disease Flashcards
what is systole
contraction and ejection of blood from ventricles
what is diastole
relaxation and filling of ventricles
pressure in systemic circulation and pulmonary circulation
systemic- high
pulmonary- low
how much blood does each ventricle pump each heart beat
70ml which is stroke volume
at a heart rate of 70bpm = 4.9 litres blood per minute
every minute your heart pumps the entirety of your blood
how long does a cardiac action potential last
280ms
what determins the opening of valves
differential blood pressure
how are cusps of valves attatched
cusps of mitrial and tricuspid valves attach to papillary muscles via chordae tendinaeae
they prevent inversion of valves on systole
what generates an action potential in the heart
pacemaker cells in the sinoatrial node
what is atrial systole
activity spreads over atria
how long is the action potential delayed in the atrioventricular node
120ms
how does an action potential spread across the heart
activity spreads across atria from SA node
reaches the atrioventricular node and delayed
from av node excitation spreads down septum between ventricles
next spreads through ventricular myocardium from inner to outer surface
ventricle contracts from the apex up forcing blood through outflow valves
what changes happen in systole and diastole when the heart beats faster
systole remains constant but diastole reduces
what are the 7 phases of the cardiac cycle
atrial contraction isovolumetric contraction rapid ejection reduced ejection isovolumetric relaxation rapid filling reduced filling
how long does diastole last
around 0.55s
how does systole last
0.35s
what side of the heart is the wiggers diagram plotted for
left
right side would be lower pressure
Phase 1
atrial contraction
atrial pressure-atrial pressure rises due to atrial systole. This is called the ‘A wave’
ventricular pressure-atrial contraction accounts for 10% of ventricular filling
electrocardiogram- p wave in ECG
what is EDV
end diastolic volume- at the end of phase 1 ventricular volumes are maximal- typically 120ml
Phase 2
isovolumetric contraction
same volume as all the valves are closed
mitrial valve closes as intraventricular pressure exceeds atrial pressure
ventricular pressure- rapid rise in ventricular pressure as ventricle contracts
atrial pressure- closing of mitral valve causes the ‘C wave’ in the atrial pressure curve
ventriculr volume- isovolumetric since there is no change in ventricular volume
electrocardiogram- QRS complex in ECG signifies onset of ventricular depolarisation
s1- closure of mitral and tricuspid valve
phase 3
rapid ejection
ejection begins when the intraventricular pressure exceeds the pressure within the aorta. This causes the aortic valve to open
ventricular volume- rapid decrease in ventricular volume as blood is ejected into aorta
mitrial/tricuspid- closed
aortic/pulmonary- open
phase 4
reduced ejection
repolarisation of ventricle leads to a decline in tension and the rate of ejection begins to fall
electrocardiogram- ventricular repolarisation depicted by T-wave of ECG
mitrial/tricuspid- closed
aortic/pulmonary- open
phase 5
isovolumetric relaxation
-when the intraventricular pressure falls below aortic pressure, there is a brief backflow of blood which causes the aortic valve to close
aortic pressure- valve closure causes dip in pressure
although rapid decline in ventricular pressure, volume remains constant since all valves are closed.
closure of aortic and pulmonary valves- S2 dub
phase 6
rapid filling
-fall in atrial pressure that occurs after the opening of mitral valve is called Y descent
ventricular volume- when intraventricular pressure falls below atrial pressure, the mitral valve opens and rapid ventricular filling begins
mitral/ tricuspid: open
aortoc/pulmonary: closed
phase 7
reduced filling
ventricular volume- rate of filling slows down as ventricle reaches its inherent relaxed volume. Further filling is driven by venous pressure
at rest the ventricles are 90% full by end of phase 7
mitral/ tricuspid valve: open
aortic/pulmonary: closed
