Circulatory responses to exercise and special circulations

Question 1

How much CO is directed to muscle during rest, and during maximal exercise?

Answer 1

Rest - 15-20%
Maximal exercise -80-85%

Decreased blood flow to less active organs - depends on metabolic rate + exercise intensity

Question 2

What is skeletal muscle vasodilation during exercise due to?

Answer 2

Autoregulation
- blood flow increase to meet metabolic demands of tissue (HYPERAEMIA)
- Magnitude of vasodilation in proportion to size of recruited muscle mass.

Question 3

What are the factors ensuring skeletal muscle vasodilation (metabolic regulations) can go into play?

Answer 3

• Tissue hypoxia
• CO2 increase
• pH decrease
• lactate production
• breakdown
  products of ATP-
  e.g. adenosine,
  inorganic phosphate
• potassium
• osmolality

Question 4

What are the 2 endothelial derived relaxing factors?

Answer 4

NO - as blood is flowing through vasculature, endothelial cells release NO.

Prostaglandins - PGs are released from tissues in inflammation (they decrease swelling)

Question 5

What is the difference between blood flow to working skeletal muscles at rest, and during max exercise?

Answer 5

• At rest, 15 to 20% of cardiac output to
  muscle.
• ↑ to 80 to 85% during maximal exercise.

Question 6

What % of CO can skeletal muscle take up during maximal exercise?

Answer 6

90%

Other major users of CO during exercise = skin, coronary circulation.

Question 7

What is visceral organs and inactive tissue vasoconstriction during exercise due to?

Answer 7

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

Question 8

How does splanchnic blood flow differ during rest and exercise?

Answer 8

Decreases during exercise.

Rest = 1500mL/min (25% CO)
Exercise = 350mL/min (5% CO)

Question 9

How does splanchnic oxygen consumption differ during rest and exercise?

Answer 9

Stays the same.

Rest + exercise =50-60mL/min

Question 10

How does splanchnic oxygen extraction differ during rest and exercise?

Answer 10

Increases during exercise (more efficient)

Rest = 15-20%
Exercise = 75%

GLUT1 transporters are sent to bring up O2.

Question 11

How much of total blood volume is in splanchnic region?

Answer 11

20-25%

Question 12

What does constriction in splanchnic circulation do?

Answer 12

Add blood volume into circulation back to the heart - increase venous return.

• Vasoconstricts even more during exercise in heat (more CO available for skin).

Question 13

Splanchnic circulation vasoconstricts during exercise. When does it vasoconstrict further?

Answer 13

During exercise in the heat = more CO available for skin.

Question 14

How would you identify someone with cervical spinal cord injury, through portal vein flow information?

Answer 14

If portal vein blood flow doesn’t decrease during exercise - it means blood flow is still going to splantic area (no redistribution/vasoconstriction)

Question 15

What happens to skin uptake of blood during exercise?

Answer 15

Increases a lot.
- rest = 100-300ml/min
- maximal = 7-8 L/min

Question 16

Cutaneous circulation (skin) - what does hot and cold stress lead to, respectively?

Answer 16

Heat - vasodilation
Cold - vasoconstriction

Question 17

Skin blood vessels are controlled by sympathetic neural control. What are the non-hairy, and hairy parts of our skin controlled by?

Answer 17

Non-hairy - adrenergic vasoconstrictor (noradrenaline as neurotransmitter)

Hairy - cholinergic vasodilatory (acetylcholine as neurotransmitter)

Question 18

Describe thermoregulation of the skin during cold stress.

Answer 18

Cold stress = VC = sympathetic constrictor activity increases (adrenergic)

Question 19

Describe thermoregulation of the skin during heat stress.

Answer 19

Heat stress = VD = sympathetic constrictor activity decreases (non-hairy) + sympathetic dilatory activity increases (hairy)

Vasodilatory effect increases once temperature threshold is reached.

Question 20

How does active vasodilation differ during dynamic exercise and during heating at rest?

Answer 20

Dynamic exercise = higher threshold.

Question 21

Do we receive a higher or lower amount of skin blood flow during exercise than we can receive compared to rest?

Answer 21

Lower

Question 22

How does renal blood flow differ between rest and exercise?

Answer 22

Renal blood flow decreases during exercise.

Rest = 1200mL/min (20% CO)
Exercise = 360mL/min (4% CO)

Question 23

How does renal oxygen extraction differ between rest and exercise?

Answer 23

Increases during exercise.

Rest = 6%
Exercise =18%