Coronary artery disease disrupts endothelial lining cells and may yield a paradoxic rise in coronary resistance. Therefore, stimulation of the sympathetic and parasympathetic nervous system may have variable response depending on the location of the activated receptors, as well as the presence of other confounding conditions.
In addition to the regulatory effects of the autonomic nervous system on coronary blood flow, the central nervous system also has direct effects on coronary resistance. Upon stimulation of certain foci in the brainstem, coronary vasoconstriction can be demonstrated. This phenomenon highlights the role of the central nervous system and emotions in modulating coronary resistance.
All of the above factors affect coronary blood flow by varying vasculature resistance. In conjunction with oxygen-carrying capacity of blood, coronary blood flow determines the oxygen delivery to the myocardium. buy diabetes drugs
Myocardial Oxygen Demand
The heart relies exclusively on aerobic metabolism for energy production under normal conditions. Fatty acids, the major myocardial substrates, are metabolized via the Krebs cycle. Oxidative phosphorylation is dependent upon the presence of oxygen in the myocardial mitochondrion. The three most important factors determining myocardial metabolism and oxygen need are as follows: