Circulatory responses to exercise and special circulations Flashcards
How much CO is directed to muscle during rest, and during maximal exercise?
Rest - 15-20%
Maximal exercise -80-85%
Decreased blood flow to less active organs - depends on metabolic rate + exercise intensity
What is skeletal muscle vasodilation during exercise due to?
Autoregulation
- blood flow increase to meet metabolic demands of tissue (HYPERAEMIA)
- Magnitude of vasodilation in proportion to size of recruited muscle mass.
What are the factors ensuring skeletal muscle vasodilation (metabolic regulations) can go into play?
- Tissue hypoxia
- CO2 increase
- pH decrease
- lactate production
- breakdown
products of ATP-
e.g. adenosine,
inorganic phosphate - potassium
- osmolality
What are the 2 endothelial derived relaxing factors?
NO - as blood is flowing through vasculature, endothelial cells release NO.
Prostaglandins - PGs are released from tissues in inflammation (they decrease swelling)
What is the difference between blood flow to working skeletal muscles at rest, and during max exercise?
- At rest, 15 to 20% of cardiac output to
muscle. - ↑ to 80 to 85% during maximal exercise.
What % of CO can skeletal muscle take up during maximal exercise?
90%
Other major users of CO during exercise = skin, coronary circulation.
What is visceral organs and inactive tissue vasoconstriction during exercise due to?
- SNS vasoconstriction
- Blood flow reduced to 20/30% of resting values
How does splanchnic blood flow differ during rest and exercise?
Decreases during exercise.
Rest = 1500mL/min (25% CO)
Exercise = 350mL/min (5% CO)
How does splanchnic oxygen consumption differ during rest and exercise?
Stays the same.
Rest + exercise =50-60mL/min
How does splanchnic oxygen extraction differ during rest and exercise?
Increases during exercise (more efficient)
Rest = 15-20%
Exercise = 75%
GLUT1 transporters are sent to bring up O2.
How much of total blood volume is in splanchnic region?
20-25%
What does constriction in splanchnic circulation do?
Add blood volume into circulation back to the heart - increase venous return.
- Vasoconstricts even more during exercise in heat (more CO available for skin).
Splanchnic circulation vasoconstricts during exercise. When does it vasoconstrict further?
During exercise in the heat = more CO available for skin.
How would you identify someone with cervical spinal cord injury, through portal vein flow information?
If portal vein blood flow doesn’t decrease during exercise - it means blood flow is still going to splantic area (no redistribution/vasoconstriction)
What happens to skin uptake of blood during exercise?
Increases a lot.
- rest = 100-300ml/min
- maximal = 7-8 L/min
Cutaneous circulation (skin) - what does hot and cold stress lead to, respectively?
Heat - vasodilation
Cold - vasoconstriction
Skin blood vessels are controlled by sympathetic neural control. What are the non-hairy, and hairy parts of our skin controlled by?
Non-hairy - adrenergic vasoconstrictor (noradrenaline as neurotransmitter)
Hairy - cholinergic vasodilatory (acetylcholine as neurotransmitter)
Describe thermoregulation of the skin during cold stress.
Cold stress = VC = sympathetic constrictor activity increases (adrenergic)
Describe thermoregulation of the skin during heat stress.
Heat stress = VD = sympathetic constrictor activity decreases (non-hairy) + sympathetic dilatory activity increases (hairy)
Vasodilatory effect increases once temperature threshold is reached.
How does active vasodilation differ during dynamic exercise and during heating at rest?
Dynamic exercise = higher threshold.
Do we receive a higher or lower amount of skin blood flow during exercise than we can receive compared to rest?
Lower
How does renal blood flow differ between rest and exercise?
Renal blood flow decreases during exercise.
Rest = 1200mL/min (20% CO)
Exercise = 360mL/min (4% CO)
How does renal oxygen extraction differ between rest and exercise?
Increases during exercise.
Rest = 6%
Exercise =18%
