Question

how does coronary blood flow change when the demand on the heart increase

Answer 1

There is continuous supply of coronary blood to heart for its proper functioning. But with the change in the demand the blood supply also changes.

The coronary flow changes in the basis of local oxygen demands. When the demand is not compensated ischemia will develop. This is to be compensated. When heart beats increase and the thus the heart rate rises so the demand increases creating a local hypoxia situation. The increased contractility of heart already cause the accumulation of vasodilators like adenosine. These act on the Beta 2 receptors and cause vasodilation which leads to the reduction in vascular resistance and thus the blood flow through the coronary vessels increase to compensate the ischemia.