Exercise and Coronary Blood Flow

Question 1

How does the body prepare for exercise?

Answer 1

• feedforward control (anticipatory)
• cardiac output and TPR adjusted
• decreases parasympathetic tone
• increases sympathetic activity
• ADH release is stimulated to promote retention of water and decrease urine production
• resets baroreceptors upwards to mute effect of increased arterial pressure on normal reflex mechanisms they would otherwise induce

Question 2

How is vasodilation stimulated in muscles in response to exercise?

Answer 2

• use of muscle increases metabolic activity
• as a result blood flow can increase
• arteriolar dilation results in decrease in TPR

Question 3

If TPR decreases during exercise how is MABP maintained?

Answer 3

cardiac output increases in response to TPR to maintain BP

Question 4

Describe blood flow to the skin in response to exercsie?

Answer 4

• at first blood flow is restricted to the skin
• as it continues, heat will be generated that needs dissipated through the skin to regulate temperature
• contributes to decrease in TPR

Question 5

Explain the effect exercise has on cardiac output

Answer 5

• increased sympathetic control
• decreases parasympathetic control
• increases cardiac output by increasing HR and SV
• veins are compressed within exercising muscles which increases venous return and can further increase EDV

Question 6

Explain the effect exercise has on the kidneys

Answer 6

• due to redistribution of cardiac output
• decreased blood flow to kidneys
• decreases urine production due to decreased pressure diuresis mechanisms
• contribution from ADH release
• contribution from increased activity of RAAS system

Question 7

Explain the effect exercise has on MABP

Answer 7

• during moderate dynamic exercise MABP increases slightly
• pulse pressure may increase due to increased systolic pressure
• slight decrease in diastolic pressure

Question 8

Explain blood perfusion and problems as a result of exercise

Answer 8

• contraction of skeletal muscle during exercise means blood perfusion is restricted to the time the muscle spends relaxed
• if insufficient time is spent in the relaxed state, blood supply may not match demand

Question 9

Describe the effect static exercise has on the body (anaerobic)

Answer 9

• prolonged muscle contractions compress both arteries and veins
• increases venous return and TPR
• local factors can attempt to dilate arterioles but physical compression from muscle contraction prevents this
• local factors accumulate in great concentration, metabotropic receptors cause an increase in exercise reflex controlling cardiac output to increase it further
• increases HR increasing CO and TPR
• MABP increases substantially

Question 10

What is dynamic exercise (aerobic)?

Answer 10

exercise that uses many muscle groups regularly over prolonged period of time

Question 11

Discuss issues with coronary blood flow during exercise

Answer 11

• myocardium cannot function anaerobically
• anaerobic glycolysis results in increased production of lactic acid
• arterioles mechanically close during systole
• decreases diastolic filling time during exercise
• increases oxygen and metabolic demand

Question 12

What effect does local metabolism have on coronary blood flow?

Answer 12

releases vasodilators

Question 13

Describe sympathetic stimulation of skeletal muscle arteries

Answer 13

• noradrenaline causes vasoconstriction of skeletal muscle arterioles by a-1 receptors
• adrenaline causes vasodilation of skeletal muscle arterioles by b-2 receptors