Week 6 - Circulatory responses to exercise Flashcards
Metabolic regulation of resistance vessels
Blood flow increases in relation to metabolic activity of a tissue/organ
Redistribution of blood flow during exercise
(ON SHEET)
Increase blood flow to working skeletal muscle - increase from 10-15% to 80-85% during maximal exercise.
Decreased blood flow to less active organs - liver, kidneys, GI tract, depends on metabolic rate, exercise intensity
Regulation of local blood flow during exercise via skeletal muscle vasodilation
Autoregulation - Blood flow increased to meet metabolic demand, magnitude of vasodilation proportional to size of recruited muscle mass and changes in EDRFs
What are endothelial derived relaxing factors (EDRFs)
(ON SHEET)
Release by shear force of flowing blood, Nitric Oxide, Prostaglandins
Vasoconstriction to visceral organs -SNS vasoconstriction, blood flow reduced to 20-30% of resting value
Cardiac output redistribution during exercise
Skeletal muscle can take up to 90% of cardiac output at maximal intensity
Cardiac output also used by skin, coronary circulation
Splanchnic circulation during exercise
Flow at rest - 1500 mL/min
25% of CO
Exercise - 350 mL/min
5% of CO
Oxygen consumption at rest - 50-60mL/min
Exercise - 50-60mL/min
Oxygen extraction at rest - 15-20%
Exercise - 75%
How is splanchnic circulation impacted during exercise
(ON SHEET)
Blood flow decreases due to sympathetic vasoconstriction and circulating catecholamines . Oxygen extraction increases to compensate
How does sympathetic neural control impact the splanchnic region
(ON SHEET)
Constriction in the splanchnic circulation can add blood volume in circulation back to the heart (increase venous return)
Vasoconstricts during exercise
Further vasoconstriction in heat - more cardiac output available at the skin
What are the skin (cutaneous) circulation measurements
rest - 100-300ml
Maximal - 7-8L/min
Sympathetic neural control of blood vessels
Adrenegergenic vasoconstrictor:
- Cold stress leads to vasoconstriction = increased sympathetic constrictor activity
Cholinogenic vasodilator -
- heat stress leads to vasodilation
- decrease in sympathetic constrictor activity
- increased sympathetic dilator activity
Skin circulation - exercise onset
Initial vasoconstriction followed by vasodilation
Skin circulation - during exercise
During dynamic exercise, active vasodilation occurs at higher threshold than at rest.
Mechanism of active vasodilation in exercise sympathetic cholinergic nerves and nitric oxide, peptides
What is the role of capillaries
Nutrient / fluid exchange
How to vasoconstriction to visceral organs and inactive tissues help regulation of local blood flow
(ON SHEET)
SNS vasoconstriction
Blood flow reduced to 20 to 30% of resting values
How can sympathetic neural control impact splanchnic circulation
(ON SHEET)
Constriction in the splanchnic circulation can add blood volume into the circulation back to the heart
Vasoconstricts during exercise
Vasoconstricts more during exercise in heat
How can skin circulation impact blood pressure regulation
Skin circulation can determine the performance of the heart
In heat blood is shifted from the core to the surface
Muscle pump cannot assist in aiding venous return so filling of heart is reduced
Means vasoconstriction must occur to maintain BP
In extreme condistions, skin vasoconstriction compromises thermoregulation
What are renal blood flow measurements at rest
Flow - 1200mL/min-1, 20% of CO
Oxygen extraction - 6%
What are the renal blood flow measurements during exercise
Flow - 360mL/min-1, 4% of CO
Oxygen extraction - 18%
What is the role of renal blood flow
Sympathetic neural control
Vasoconstriction in exercise
Potential for proteinuria in intense exercise
As Hr increases renal blood flow decreases
