Excercise & the CV system

Question 1

What are 4 demands on the CVS in exercise?

Answer 1

Increase O2 uptake
Increase O2 transport
Direct increased O2 supply to exercising muscle
Stabilize blood pressure

Question 2

How are these demands of exercise met (6 things)?

Answer 2

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

Question 3

How is pulmonary blood flow increased?

Answer 3

Increase RV output

Question 4

How is O2 uptake increased?

Answer 4

Increased pulmonary blood flow
Filling blood to a higher extent with oxygen

Question 5

How is VO2 calculated by?

Answer 5

CO X A-Vo2 difference

Question 6

How is CO increased during exercise?

Answer 6

Increased HR and SV

Question 7

What happens to SV after a while?

Answer 7

Reaches a limit after it reaches 120 therefore rate is main factor at high loads

Question 8

How is HR increased?

Answer 8

Increased stimulation of the SA and AV nodes

Question 9

What 3 things increase stimulation of SA and AV nodes?

Answer 9

Decreased vagal parasympathetic activity
Increased cardiac sympathetic fibre activity
Increased circulating catecholamines

Question 10

Which 2 catecholamines are increased?

Answer 10

Adrenaline from adrenal medulla
NA spill over from sympathetic nerve terminals

Question 11

What are 3 things that increase SV in exercise?

Answer 11

Increase in preload in upright exercise
Faster ejection
Substantial decrease in EDV

Question 12

What 3 things is preload increased by?

Answer 12

Increase in central venous pressure
peripheral venoconstriction & calf muscle pump
Activates Starling’s Law of heart -> contractile force

Question 13

What is faster ejection due to?

Answer 13

Sympathetic activation of Beta 1 adrenergic receptors

Question 14

What is decrease in EDV due to?

Answer 14

Increased contractility of sympathetic activation of myocardial beta 1 receptors

Question 15

What causes vasodilation in active muscles?

Answer 15

Fall in local resistance due to metabolic vasodilation

Question 16

What 2 other places does vasodilation occur?

Answer 16

Myocardium (coronary arteries)
skin (temp. regulation)

Question 17

What could reduced vascular resistance in active muscle and skin cause?

Answer 17

BP to fall despite increased CO

Question 18

How is hypotension in exercise avoided by?

Answer 18

Compensatory vasoconstriction in non-active tissues -> attentuates fall in TPR

Question 19

What is metabolic hyperaemia due to?

Answer 19

Locally released vasodilators

Question 20

What are 8 vasodilators?

Answer 20

K+
Adenosine
CO2
Lactate
Phosphate
Hyperosmolarity
H2O2
NO

Question 21

What 2 things initiates muscle vasodilation?

Answer 21

Metabolic hyperemia (intrinsic)
Increased BP

Question 22

What 2 things do not contribute significantly to non-emotional muscle vasodilation?

Answer 22

Sympathetic nerves
Hormones

Question 23

What 2 things contribute to altered para/sym-pathetic activity increasing CO during exercise?

Answer 23

Central command
Peripheral reflex from muscle work receptors

Question 24

What does the contribution of the central command explain?

Answer 24

Brisk onset of cardiac response nut not linear relation of CO to muscle O2 consumption

Question 25

What does the contribution of the peripheral reflex explain?

Answer 25

Linear linkage of CO to muscle O2 consumption

Question 26

What 2 nerve fibres influence para/sym-pathetic tone?

Answer 26

III afferent
IV afferent

Question 27

What 2 receptors contribute to peripheral reflex?

Answer 27

Mechanoreceptors
Chemosensitive metaboreceptors