Cardiovascular Physiology: Cardiac Output, Stroke Volume, and Ejection Fraction. We will do a little calculation here together for End Systolic Volume (ESV). Physiology is not only vital to score well on your USMLE Step 1 but it is the foundation of medical science. You have to know how your body works properly in order to understand pathology and treatment options such as pharmacology and how specific medication works on our body. I hope this Information is useful for health field students. Bes