Question

1_ What is the Frank-Starling law of the heart? And why the heart cannot function on the descending limb of the Starling curve?

2- What cause the low cardiac efficiency (around 20% or less)?

please answer clear and if you are sure
Thank you

Answer 1

1. The relationship between the stroke volume and end diastolic volume of the heart is given by Frank-starling law of the heart. this law states that before contraction (i.e., the end-diastolic volume), as the volume of blood in the ventricles increases, the volume of heart also increases. Flow of a large volume of blood into the ventricles causes stretching of the muscle fibers that increase the force of contraction. Starling noticed that heart normally functions on the left-hand portion (or the ascending limb) of the starling curve but not on the descending limb because at the ascending limb, increasing preload increases the ability of heart to empty. However, on the descending limb, this ability is lost. This increases the end-systolic volume. This, in turn, increases the load on EDV. The heart has no way to cope with this problem and would burst due to overfilling of blood.
2. A low cardiac efficiency generally means that there may be issues with cardiac pumping function. This can be due to certain heart disease, a low blood volume, or bradycardia. A low cardiac efficiency results in ejection of less volume of blood from the heart, which means that the cardiac output from the heart is decreased.