Excercise & the CV system Flashcards
What are 4 demands on the CVS in exercise?
Increase O2 uptake
Increase O2 transport
Direct increased O2 supply to exercising muscle
Stabilize blood pressure
How are these demands of exercise met (6 things)?
Increase rV output
Increase LV output
Increase O2 extraction from muscle blood
Decrease vascular resistance in exercising muscle
vasoconstriction in non-exercising tissues
baroreflex re-set
How is pulmonary blood flow increased?
Increase RV output
How is O2 uptake increased?
Increased pulmonary blood flow
Filling blood to a higher extent with oxygen
How is VO2 calculated by?
CO X A-Vo2 difference
How is CO increased during exercise?
Increased HR and SV
What happens to SV after a while?
Reaches a limit after it reaches 120 therefore rate is main factor at high loads
How is HR increased?
Increased stimulation of the SA and AV nodes
What 3 things increase stimulation of SA and AV nodes?
Decreased vagal parasympathetic activity
Increased cardiac sympathetic fibre activity
Increased circulating catecholamines
Which 2 catecholamines are increased?
Adrenaline from adrenal medulla
NA spill over from sympathetic nerve terminals
What are 3 things that increase SV in exercise?
Increase in preload in upright exercise
Faster ejection
Substantial decrease in EDV
What 3 things is preload increased by?
Increase in central venous pressure
peripheral venoconstriction & calf muscle pump
Activates Starling’s Law of heart -> contractile force
What is faster ejection due to?
Sympathetic activation of Beta 1 adrenergic receptors
What is decrease in EDV due to?
Increased contractility of sympathetic activation of myocardial beta 1 receptors
What causes vasodilation in active muscles?
Fall in local resistance due to metabolic vasodilation
What 2 other places does vasodilation occur?
Myocardium (coronary arteries)
skin (temp. regulation)
What could reduced vascular resistance in active muscle and skin cause?
BP to fall despite increased CO
How is hypotension in exercise avoided by?
Compensatory vasoconstriction in non-active tissues -> attentuates fall in TPR
What is metabolic hyperaemia due to?
Locally released vasodilators
What are 8 vasodilators?
K+
Adenosine
CO2
Lactate
Phosphate
Hyperosmolarity
H2O2
NO
What 2 things initiates muscle vasodilation?
Metabolic hyperemia (intrinsic)
Increased BP
What 2 things do not contribute significantly to non-emotional muscle vasodilation?
Sympathetic nerves
Hormones
What 2 things contribute to altered para/sym-pathetic activity increasing CO during exercise?
Central command
Peripheral reflex from muscle work receptors
What does the contribution of the central command explain?
Brisk onset of cardiac response nut not linear relation of CO to muscle O2 consumption
What does the contribution of the peripheral reflex explain?
Linear linkage of CO to muscle O2 consumption
What 2 nerve fibres influence para/sym-pathetic tone?
III afferent
IV afferent
What 2 receptors contribute to peripheral reflex?
Mechanoreceptors
Chemosensitive metaboreceptors
