9. Exercise and Coronary Blood Flow Flashcards
What are the main issues associated with coronary blood flow?
Myocardium cannot function anaerobically
Arterioles close mechanically during systole
Decreased diastolic filling during exercise
Increase oxygen and metabolic demand during exercise
At what rate does the work rate of the heart increase during exercise?
6-9x during strenuous exercise
What % of coronary blood flow oxygen is used at rest?
70-80%
What is the primary controller of coronary blood flow?
local metabolism
- in proportion to the need of cardiac musculature for O2
- stimulates the release of vasodilators (adenosine)
How does sympathetic stimulation affect coronary blood flow
Indirectly via increase in HR and increased contractility which increases metabolism
Directly; high degree of sympathetic innervation
What is the affect of NA on skeletal muscle arterioles
vasoconstriction via alpha-1 receptors
What is the affect of adrenaline on skeletal muscle arterioles?
vasodilation via beta-2 receptors
What are the more dominant receptors?
beta-2
What are the changes on cardiac distribution of cardiac output during exercise
heart and muscle - hyperaemia
Skin
- increased core temperature; detected by the hypothalamus
- decreased sympathetic innervation of the skin
What is the affect of moderate exercise of MABP?
small increase if any at all
What happens to pulse pressure during exercise?
INCREASES
- systolic pressure increases due to increased stroke volume and increased speed of ejection
What happens to cardiac output during moderate exercise
Increased
What happens to HR during moderate exercise?
Increases
Decreased PSNS and increased SNS innervation at the SA node
What happens to stroke volume during moderate exercise?
Increased
increased contractility and frank-starling
Factors that promote venous return during exercise
Muscle pumps
frequency and depth of inspiration
Increased venous tone via SNS
