Week 6 - Circulatory responses to exercise

Question 1

Metabolic regulation of resistance vessels

Answer 1

Blood flow increases in relation to metabolic activity of a tissue/organ

Question 2

Redistribution of blood flow during exercise
(ON SHEET)

Answer 2

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

Question 3

Regulation of local blood flow during exercise via skeletal muscle vasodilation

Answer 3

Autoregulation - Blood flow increased to meet metabolic demand, magnitude of vasodilation proportional to size of recruited muscle mass and changes in EDRFs

Question 4

What are endothelial derived relaxing factors (EDRFs)
(ON SHEET)

Answer 4

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

Question 5

Cardiac output redistribution during exercise

Answer 5

Skeletal muscle can take up to 90% of cardiac output at maximal intensity
Cardiac output also used by skin, coronary circulation

Question 6

Splanchnic circulation during exercise

Answer 6

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%

Question 7

How is splanchnic circulation impacted during exercise
(ON SHEET)

Answer 7

Blood flow decreases due to sympathetic vasoconstriction and circulating catecholamines . Oxygen extraction increases to compensate

Question 8

How does sympathetic neural control impact the splanchnic region
(ON SHEET)

Answer 8

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

Question 9

What are the skin (cutaneous) circulation measurements

Answer 9

rest - 100-300ml
Maximal - 7-8L/min

Question 10

Sympathetic neural control of blood vessels

Answer 10

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

Question 11

Skin circulation - exercise onset

Answer 11

Initial vasoconstriction followed by vasodilation

Question 12

Skin circulation - during exercise

Answer 12

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

Question 13

What is the role of capillaries

Answer 13

Nutrient / fluid exchange

Question 14

How to vasoconstriction to visceral organs and inactive tissues help regulation of local blood flow
(ON SHEET)

Answer 14

SNS vasoconstriction
Blood flow reduced to 20 to 30% of resting values

Question 15

How can sympathetic neural control impact splanchnic circulation
(ON SHEET)

Answer 15

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

Question 16

How can skin circulation impact blood pressure regulation

Answer 16

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

Question 17

What are renal blood flow measurements at rest

Answer 17

Flow - 1200mL/min-1, 20% of CO
Oxygen extraction - 6%

Question 18

What are the renal blood flow measurements during exercise

Answer 18

Flow - 360mL/min-1, 4% of CO
Oxygen extraction - 18%

Question 19

What is the role of renal blood flow

Answer 19

Sympathetic neural control
Vasoconstriction in exercise
Potential for proteinuria in intense exercise
As Hr increases renal blood flow decreases