According to Frank-Starling law, extent of the preload is proportional to
Correct Answer: End-diastolic volume
Description: i.e. (End-diastolic volume): (515-Ganong 23rd) (181-82- AK jain 4th)Starling's law of the heart or Frank-Starling lawThe length of the cardiac muscle fibers (i.e. the extent of the preload) is proportional to the end, diastolic volume (EDV)"Energy of contraction is proportional to the initial length of the cardiac muscle fiber"The relation between ventricular stroke volume and end diastolic volume is called the Frank-Sterling curveEDV measures the 'passive' tension i.e. diastolic intraventricular pressureSignificance of Frank-Starling Law(I) The law helps up to explain that blood ejected by each of the ventricle per heart beat is the same. If RV out put per beat exceeds LV output. This will cause accumulation of blood in LV; the Frank Starling law begins to operate causing more complete evacuation of LV. Thus the out put of two ventricles becomes the same again(II) It is a life saving device in cardiac failure. How? LVF causes accumulation of blood within LV thereby decreases blood supply to vital organs. However accumulation of blood in LV initiates operation of Frank Starling mechanism leading to greater output by LV If accumulation of blood is too great, the Frank Starling law will fail to operate, decreasing blood supply to vital organs and finally leads to death.* During diastole, filling of the ventricles normally increases the volume of each ventricles to about 110 to 120 ml, this volume is known as end-diastolic volume
Category:
Physiology
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