PHYS 1302 Lecture 2: integrative-physiology-ch-25-partial

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16 Aug 2018
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Exercise causes sympathetic activation that increases cardiac output and causes vasoconstriction in peripheral arteries. Cardiac output rises dramatically during strenuous exercise: from 5 l/min to 20 l/min (normal individuals, from 5 l/min to 40 l/min (athletes) Due to decrease in parasympathetic activity at sa node. Sympathetic stimulation on heart during exercise increases contractility of the heart (increased stroke volume) and increases heart rate. Blood pressure rises only slightly during exercise because of skeletal muscle vasodilation. At rest, skeletal muscle receives of the cardiac output. At the onset of exercise, sympathetic signals cause vasoconstriction in peripheral tissues: as muscles become more active, o2 concentration decreases, temperature increases, co2 concentration increases local vasodilation. Shift of blood flow from inactive tissues to exercising muscles (where needed) Since co increases so significantly, the relative percentages may be smaller but more blood flow altogether. Since cardiac output increases during exercise, blood pressure increases. Skeletal muscle vasodilation decreases peripheral resistance, however.

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