explain the pressure volume loop
isvolumetric contraction
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Mitral valve closed - closes before in phase 1 atrial contraction
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systole (ventricular contraction) begins
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no changes to ventricular volume (mitral and aortic valve closed)
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pressure increases
o
from end diastolic vol point, goes straight up as pressure increases but lv vol
stays the same
ventricular ejection
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LV pressure > aortic pressure
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=> aortic valve opens at the start of curve
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blood is ejected
o
as blood is ejected the lv volume decreases, ventricles have contracted so
pressure in ventricles is also increasing causing curve towards left
isovolumetric relaxation
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at end of systole aortic valve closes when aortic pressure > LV pressure
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ventricles start to relax so LV pressure decreases
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ESV = 70ml
ventricular filling during diastole
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at start, mitral valve opens
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LV is filled (EDV ), LV is relaxed and distended
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pressure increases edv = 140ml
What happens if we increase preloadinc preload
-> increasing EDV - adding more blood to LV during diastole
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increase stregnth of contraction
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increase stroke volume
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larger loop
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stroke work inc
What happens if we increase afterload
inc afterload - inc blood pressure in the entire arteriole system
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increas ventriclular pressure during isovolumetric contraction has to rise higher before it exceeds aortic pressure so aortic
valve opens
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less blood leaves ventricle
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increase end systolic volume
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decrease stroke volume
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loop narrower and taller
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smaller sv, higher pressure - stroke work remains relatively
stable
what happens to pressure volume loop if we increase
contractilityblood under higher pressure
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longer ejection phase
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left ventricular pressure = aortic pressure
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increase stroke volume, stroke work
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decrease ejetion fraction, edv
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loop widens
RIGHT ATRIUM
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SVC and IVC openings
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fossa ovalis - remenant of embryonic foramen ovale
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crista terminalis - pectinate muscles
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LEFT ATRIUM
•
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smooth chamber wall with no ridges (pectinate only in left
auricle)
opening for pulmonary veins
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RIGHT VENTRICLE
LEFT VENTRICLE
tricuspid valve
traberculae carnae
bicuspid valve
2 papillary muscles
3 papillary muscles
traberculae carnae