Contractility Flashcards
what is preload
most accurately, the amount of wall tension in RV or LV just before contraction is initiated
End diastolic fiber length
what is afterload
pressure required to eject blood (open aortic/pulmonary valve)
what happens to the pressure volume loops if you increase preload
increase EDV
increase stroke volume
(more venous return, more blood volume)
what happens to the pressure volume loops if you increase afterload
greater pressure needed to open valves leads to higher pressure during ejection
reduced SV and EF
(aortic stenosis, hypertension)
what happens to the pressure volume loops if you increase contractility
increase SV and EF
less blood left in the heart
(adrenergic stimulation)
where in the heart does parasympathetic innervation have a negative inotropic effect
atria only
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mAChR activation
decreases inward Ca current during plateau; Ach increases outward K current via K-ACh channel
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what does an enhanced cardiac function curve mean
increased:
- inotropy
- HR
decreased:
-afterload
what does a depressed cardiac function curve mean
increased:
-afterload
decreased:
- inotropy
- HR
in cardiac failure…
decreased inotropy and vascular compliance
increased blood volume and SVR
