Lecture 21 (Part 1): Skeletal Muscle Blood Flow

Question 1

How does blood flow to rested and exercising muscles differ?

Answer 1

Increases massively in exercised muscle

Question 2

What is the relationship between blood flow to exercising muscles and exercise intensity?

Answer 2

Blood flow to exercising muscles increases with intensity

Question 3

What are the units of measurement for muscle blood flow?

Answer 3

ml.min.100g

Question 4

What can be measured in the arteries/veins to determine blood flow?

Answer 4

Arterial inflow
Venous outflow
Substance wash-out

Question 5

How does venous-occlusion therapy work?

Answer 5

Two cuffs.
Wrist cuff has higher pressure than systolic pressure (220mmHg), therefore cutting off blood flow to the hand.
Arm cuff produces a pressure that allows arterial inflow but prevents venous outflow (40mmHg).
Rate of swelling of the arm is proportional to arterial inflow.
This is measured by a gauge around the forearm.

Question 6

What are the pros and cons of the VOT?

Answer 6

Pros: easy & non-invasive
Cons: non-exercising & skin and fat are confounding

Question 7

What are the values for skeletal muscle blood flow for the VOT?

Answer 7

50-70 ml.min.100g

Question 8

How does thermodilution blood flow measurement work?

Answer 8

Insert catheter into vein.
Secretes an ice-cold saline solution.
Rate of change of temperature is proportional to the rate of venous outflow.
Change in temperature is measured by a thermistor.

Question 9

What are the pros and cons of the thermodilution technique?

Answer 9

Pros: exercising
Cons: invasive & requires skilled lab technician

Question 10

What are the values for skeletal muscle blood flow via the thermodilution technique?

Answer 10

250 ml.min.100g

Question 11

How does the Doppler Ultrasound measure blood flow?

Answer 11

Emits a high frequency wavelength.
This allows the measurement of blood flow.
This is identified by the equation: BF = CSA * RBC Velocity

Question 12

What are the pros and cons of the Doppler Ultrasound?

Answer 12

Pros: non-invasive, exercising & continuous
Cons: expensive & limited to large arteries near skin surface

Question 13

What is the measurement of blood flow for Doppler Ultrasounds?

Answer 13

300 ml.min.100g

Question 14

What is microdialysis?

Answer 14

Measures the rate of substance wash out using a perfusate.

Question 15

What are the pros and cons of microdialysis?

Answer 15

Pros: exercising & can measure metabolites
Cons: invasive & damaged tissue can severely impact the results