During exercise, the redistribution of cardiac output directs more blood to skeletal muscles to meet oxygen demand. What is this mechanism called?

• A. Haemoglobin
• B. Myoglobin
• C. Vascular Shunt Mechanism
• D. A-VO2 Difference

Answer: (C)

The main concept is how the body redirects blood flow to meet the oxygen needs of working muscles, using the vascular shunt mechanism. During exercise, sympathetic activity constricts vessels to non-essential areas (like the gut, kidneys, and skin) and signals arterioles in skeletal muscles to dilate in response to local metabolites (such as increased CO2, lactic acid, and adenosine). This coordinated vascular adjustment increases blood flow to active muscles, boosting oxygen delivery to meet demand.

Haemoglobin and myoglobin relate to carrying and storing oxygen, not the redistribution of blood flow, and the A-VO2 difference reflects how much oxygen is extracted by tissues rather than how blood is directed around the body.