Practice Test 11

An exercise physiologist is studying blood flow to skeletal muscle during intense activity. Local metabolic byproducts cause significant vasodilation in the exercising muscle, dramatically increasing blood flow. According to the Poiseuille equation for fluid flow, which of the following factors has the most profound influence on blood flow?

A 68-year-old man with chronic systolic heart failure is being evaluated. His physician explains that his heart's ability to pump blood is reduced. According to the Frank-Starling mechanism, which of the following variables, when increased, would most directly increase this patient's stroke volume?