College Answer

Candidates were expected to present the cellular mechanisms underlying the control of 
skeletal muscle blood flow. Many candidates correctly identified a role for sympathetic 
nervous system, metabolic (e.g. vasodilator metabolites such as CO2, H+, K+, lactate and 
adenosine), vasoactive substances released by endothelium (nitric oxide, prostacyclin, 
endothelin 1, etc.) and autoregulatory control but failed to present any details of direction 
and magnitude of control. Better answers also mentioned humeral (e.g. catecholamines, 
vasopressin, ANP, angiotensin II, histamine, serotonin, etc.) or myogenic control (i.e. when 
the pressure within a smooth muscle blood vessel is suddenly increased, the vascular 
smooth muscle is stretched.