Figure 1. Neural pathways for sympathetic activation in response to surgery. Painful stimuli transmitted through afferent nociceptive pathways activate sympathetic efferent pathways. Sympathetic stimulation of the myocardium increases heart rate (HR) and inotropy. Stimulation of the peripheral vascular bed produces vasoconstriction with a resulting increase in blood pressure (BP). EPI = epinephrine; NEPI = norepinephrine.