The regulation of the coronary blood flow is a complex process incorporating several factors. The most important of these are: 1) metabolic control; 2) autoregulation; 3) extravascular compressive forces; 4) diastolic phase in cardiac cycle; 5) humeral factors; and 6) neural control. buy asthma inhaler
Metabolic control: The changes in metabolic rate of myocardial cells are very closely linked to blood flow; This coupling mechanism acts within one cardiac cycle, and maximal coronary dilation or constriction can be elicited within 15 to 20 s. The mediator (or mediators) responsible for the coupling of myocardial metabolic rate to coronary vascular resistance remains unknown. The putative mediator is constantly produced by the myocardium, is released into the inters-titium, and cleared by the blood flow. This metabolite may act as a potent coronary vasodilator. When the myocardial metabolism exceeds a previously established steady state, the production of this substrate increases, and it may accumulate. A higher amount of mediator induces coronary vasodilation, facilitates clearance, and the steady state concentration of this substrate is re-established. Several mediators have been proposed that may fulfill the above requirements: adenosine, molecular oxygen, H +, carbon dioxide, K+, etc.