Cardiac work in the isolated heart from normal rats following acute MI
Juea Park
INTRODUCTION The heart is a muscular oragn which has to perform work to eject blood for the right and left entricles. Two laws govern the relationship between ventricular volume and cardiac pump performance. The first, the law of Laplace, is a low stating that when the ventricle dilates, the wall stress needed to achieve a give intraventricular pressure is increased. The second, Starling’s law of the heart, is a physiological law which states that when a ventricle dilates, its ability to perform work increases. In a normal heart operating within the normal range of diastolic pressures, the physiological law predominates: when the ventricle dilates, the increased capacity to generate pressure is more important than the increased wall stress. However, in patients with heart failure, the increased wall stress caused by ventricular dilation adds to the energy cost of cardiac contraction, so that the detrimental effects of increasing ventricular volume can outweigh the beneficial effects. In pathological conditions such as acute myocardial infarction, the ability of the left ventricle to perform cardiac work is significantly impaired because …show more content…
Adrenaline in the bloodstream achieves its effects on heart rate by stimulating the adrenergic receptors on cells throughout the heart tissue. Epinephrine 's binding to these receptors triggers a number of metabolic changes. High levels of epinephrine causes contraction of the smooth muscle that lines most arterioles. The way in which adrenaline acts on the sinoatrial node to accelerate the heart rate has hitherto been obscure. However, in various other parts of the heart adrenaline increases the slow inward (Ca2+/Na+)
Juea Park
INTRODUCTION The heart is a muscular oragn which has to perform work to eject blood for the right and left entricles. Two laws govern the relationship between ventricular volume and cardiac pump performance. The first, the law of Laplace, is a low stating that when the ventricle dilates, the wall stress needed to achieve a give intraventricular pressure is increased. The second, Starling’s law of the heart, is a physiological law which states that when a ventricle dilates, its ability to perform work increases. In a normal heart operating within the normal range of diastolic pressures, the physiological law predominates: when the ventricle dilates, the increased capacity to generate pressure is more important than the increased wall stress. However, in patients with heart failure, the increased wall stress caused by ventricular dilation adds to the energy cost of cardiac contraction, so that the detrimental effects of increasing ventricular volume can outweigh the beneficial effects. In pathological conditions such as acute myocardial infarction, the ability of the left ventricle to perform cardiac work is significantly impaired because …show more content…
Adrenaline in the bloodstream achieves its effects on heart rate by stimulating the adrenergic receptors on cells throughout the heart tissue. Epinephrine 's binding to these receptors triggers a number of metabolic changes. High levels of epinephrine causes contraction of the smooth muscle that lines most arterioles. The way in which adrenaline acts on the sinoatrial node to accelerate the heart rate has hitherto been obscure. However, in various other parts of the heart adrenaline increases the slow inward (Ca2+/Na+)