Lecture 11 - Cardiovascular responses to exercise

Question 1

What are the goals of the cardiovascular response to exercise?

Answer 1

Increase )2 supply to skeletal and cardiac muscle

Facilitate Co2 and heat removal

Maintain MAP - so you don’t faint - heart is working against gravity to provide blood to brain. MAP is the driving force

Question 2

VO2 = ___

Answer 2

CO x (CaO2 - CvO2)

Question 3

MAP =

Answer 3

CO x TPR

Question 4

What are the main changes in distribution of CO and blood flow during exercise?

Consider the following areas of circulation

Splanchnic, Renal, Cerebral, Coronary, Muscle, Skin

Answer 4

With exercise:

Muscle receives alot more

Splanchnic bed (liver and gut) is markedly reduced, along with renal blood flow

cerebral blood flow is maintained (rest = maximal exercise)

Coronary - increased, but doesn’t need that much (it’s very effective)

Skin - increase with light and heavy exercise. but at maximal level drops right down

Question 5

What is Hyperaemia?

Answer 5

Increase in muscle blood flow

Question 6

What causes exercise hyperaemia?

Answer 6

metabolic vasodilators from contracting skeletal muscle, endothelium and/or RBC (When the oxygen is released, other factors are as well which cause vasodilation. Also desensitise vasculature to the symp nerves which normally cause vasodilation

Muscle pump - good for maintaining blood flow, key for venous return

“Conducted Vasodilation” - relates to factors in the muscle/capilliaries. Smooth muscle has signalling (through gap junctions) which signal proximal parts of the circulation, the arterioles, to dilate.

Functional sympatholysis - Symp. nerves in muscle vasocontrict so need to turn them off.

Question 7

What are some of the vasodilator metabolites?

Answer 7

K+ (when muscles contract, they loose potassium), H+ , adenosine, ATP (comes from muscle + RBC)

ROS -

NO, prostacyclin, Prostaglandin E2

Endothelial derived hyperpolarising factor

ATP released from RBC

Question 8

Can you just inhibit one of these metabolites for vasodilation and see a reduction in blood flow?

Answer 8

No, there are many (usually a sign of an important physiological function)

would need to block 3/4 before you’ll see effects

Question 9

At a sub-maximal VO2 would you be able to tell the difference between a trained and untrained person based on CO

Answer 9

No, at lower levels they woul dhave the same CO (it’s a linear relationship)

Question 10

How does HR and Stroke volume differ in trained and untrained people?

Answer 10

At a given VO2 - The HR is much lower in the trained athlete, and hence the stroke volume is higher

This would need to be the case as the CO is the same for both, but achieved in different ways

Question 11

What happens to BP during exercise and is it different between trained/untrained subjects?

Answer 11

not very different b/w trained/untrained

Question 12

What are the determinants of Mean, systolic, diastolic pressure?

Answer 12

Systolic - When the BP is contracting so mainly influenced by CO

Diastolic is when the heart is relaxing - so is largely determined by peripheral resistance

Question 13

generally MAP goes __ during exercise

Answer 13

up

Question 14

Stroke volume decreases after long duration of exercise becaue…

Answer 14

the distolyic phase doesn’t fill the ventricles as much

Question 15

SO what are the cardiovascular responses to prolonged exericse?

Answer 15

HR rises consistently

TPR rises steadily

blood volume slowly decreases

Arterial blood pressure will drop a little bit

CO slows

skin blood flow slows

Stroke volume decreaes

Question 16

What casues the cardiovascular drift during prolonged exercise?

Answer 16

Increased HR and decreased SV

Hyperthermia - as you get hotter the SA node depolaises more rapidly

Dehydration

Increased plasma [adrenaline]

Peripheral displacement of blood volume due to cutaneous vasodilation - as you heat up, blood goes to skin

Question 17

Where is there feedback in the neural controls of this?

Answer 17

baroreceptors, neurons in the muscle (type 3/4 afferents)

feeedback and say the central command is either appropriate or not

Question 18

The Vagus nerve to the heart is…

Answer 18

inhibitory - parasympathetic

Question 19

The rising HR is initially due to withdrawn signalling from the __ and then an increase in _____ activity

Answer 19

The rising HR is initially due to withdrawn signalling from the Vagus and then an increase in Sympathetic activity

Question 20

Alot of what happens in aging is related to

Answer 20

inactivity

Question 21

What happens with cardiovascular adaptations when you train?

Answer 21

COmax goes up

Max HR doesn’t cahnge

Stroke volume increases (big benefit)

Question 22

Why is there an increase in Stroke volume on trained subjects?

Answer 22

Expanded blood volume (Frank-starling mechanism)

Increase heart size

Increase LV mass and chamber size

Increase adrenergic sensitivity

Question 23

What are the microvascular adaptations to exercise training?

Answer 23

Increase in capillary density and capillary recruitment - increases oxygen delivery and exchange