The cutaneous circulation has a potential capacity for blood flow of around 8 liters/minute, second only to active skeletal muscle in terms of a potential magnitude for blood flow. Consequently, the skin has importance for temperature regulation, blood pressure regulation and general cardiovascular homeostasis. Largely controlled by reflexes (noradrenergic as well as an active vasodilator system), resistance vessels in skin participate in thermoregulatory reflexes (internal temperature, skin temperature) and in non-thermoregulatory reflexes (baroreceptors, reflexes associated with exercise, diving reflex).
The aim of this proposal is a further exploration of the integration of these reflexes, specifically the integration of thermoregulatory and non-thermoregulatory reflexes. Thus, the independent roles of muscle mass, mode of exercise and level of exercise in the reflex vasoconstrictor control of the cutaneous vasculature will be determined in order to better understand the reflex stimuli associated with exercise in promoting reflex regional vascular responses and in competing with thermoregulatory reflexes in the control of skin blood flow. The role of skin temperature in the cutaneous vasodilation and the changes in cardiac output accompanying prolonged dynamic exercise will be determined. The integration of thermoregulatory and nonthermoregulatory reflexes in determining vasoconstrictor and vasodilator activities will be investigated by examining cutaneous vasodilator responses to baroreceptor stimulation in cool, neutral and warm conditions. The diving reflex will be studied at different temperatures to find the extent to which the cutaneous participation is strictly a thermoregulatory response. We will also explore regional heterogeneity in the cutaneous vascular responses in the above reflex responses. Only through increasing our understanding of this integrative control of skin blood flow can we fully appreciate the impact of heat stress on a circulatory system compromised by disease.
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