L20 Skeletal Muscle Blood Flow in Exercise: Oxygen Delivery

Question 1

Explain how rhythmic + static muscle contractions impact on flow through active muscle and how it relates to fatigue

Answer 1

Rhythmic –> contraction impedes blood flow. Duty cycle
Static –> flow may be obstructed because of intramuscular pressure. Increased flow post-exercise
–> lack of flow causes fatigue

Question 2

Discuss how microcirculatory blood flow differs accordingly to skeletal muscle fibre

Answer 2

Increases in blood flow during exercise are greatest in the fibres with the greatest oxidative capacity (type 1)

Question 3

List the typical partial pressure of oxygen and carbon dioxide at rest and maximal physical activity in alveoli, arterial blood, active muscles and mixed-venous return

Answer 3

Alveoli
O2 = 100mmHg
CO2 = 40 mmHg

Arterial blood
O2 = 100 mmHg
CO2 = 40 mmHg

Active muscles
O2 = 40 mmHg
CO2 = 46 mmHg

Venous blood
O2 = 40 mmHg
Co2 = 46 mmHg

Question 4

Discuss the role partial pressure plays in loading and unloading metabolic gases in the lungs and tissues

Answer 4

The gradient allows gases at a higher pressure at one location to diffuse to the area with a lower partial pressure

Question 5

Plot the oxyhaemoglobin dissociation curve

Answer 5

you know what this looks like

Question 6

What does the relationship between blood O2 content and exercise intensity look like

Answer 6

In the purple book

Question 7

Explain how capillary density and tortuosity affect the surface area for exchange of oxygen from red blood cell to muscle cell

Answer 7

The greater the capillary density the more slow twitch the fibre and the more likely that oxygen will exchange.
the more tortuous, the higher the exchange rate

Question 8

Explain the terms diffusion distance and transit time

Answer 8

Diffusion distance = distance is decreased so diffusion rate increases

Transit time = time it takes for substance to cross a membrane

Question 9

what is the correct concept of ‘capillary recruitment’ in relation to oxygen delivery

Answer 9

number of capillaries containing red blood cells increases with increasing metabolic demand

Question 10

Describe the features of the microcirculation that optimise oxygen delivery to skeletal muscle in exercise

Answer 10

• Diffusion distance - capillary density fibre size
• surface contact area
• Capillary perfusion
• Red blood cell count transit times, velocity and flux
• Haemoconcentration