Physiology 9 - Exercise and Blood Flow through Special Regions

Question 1

When does coronary perfusion occur and why?

Answer 1

During diastole, since during systole the coronary vessels are being constricted

Question 2

What happens if the diastole window shortens?

Answer 2

Negative impact on the heart, since not enough coronary perfusion can occur and cardiac muscle can’t be supplied with sufficient oxygen —> lactic acid build up & angina

Question 3

How does vasodilation of coronary arteries occur?

Answer 3

Build up of local factors

Question 4

Which hormones/neurotransmitters contribute to vasoconstriction?

Answer 4

Noradrenaline

Adrenaline

Question 5

Which hormones/neurotransmitters contribute to vasodilation?

Answer 5

Adrenaline

Question 6

Which receptors do vasoconstriction and vasodilation use?

Answer 6

alpha-1

beta-2

Question 7

What happens to total peripheral resistance during dynamic exercise?

Answer 7

Decreases due to vasodilation occurring

Question 8

What will happen to diastolic pressure during dynamic exercise?

Answer 8

If anything, decrease slightly

Question 9

What is the pulse pressure?

Answer 9

Difference between systolic and diastolic pressures

Question 10

What is the equation used in Fick’s Principle for calculating CO?

Answer 10

CO (L/min) = Rate of O2 consumption (ml/min) / Arteriovenous O2 difference (ml/L of blood)

Question 11

In the case of an area of ischaemic lung tissue, how does distribution of blood flow differ than to an ischaemic area of tissue anywhere else in the body?

Answer 11

Since the ischaemic area of lung tissue is not undergoing gaseous exchange, vasodilation to allow increased blood flow to this area would be pointless, so instead vasoconstriction occurs, due to an unknown mechanism

Question 12

What areas of the heart does the right coronary artery supply?

Answer 12

Walls of RA & RV
SA & AV nodes
Posterior (inter ventricular) septum (inc. proximal Bundle of His)

Can supply small areas of LA & LV in some people

Question 13

What areas of the heart does the right coronary artery supply?

Answer 13

Walls of LA & LV
Most of (inter ventricular) septum (inc. most of Bundle of His)

Question 14

Where do the great and small cardiac veins drain to?

Answer 14

Coronary sinus –> RA

Question 15

When is the cardiac muscle being perfused by the coronary arteries?

Answer 15

During diastole

Question 16

Why is the cardiac muscle only perfused during diastole?

Answer 16

Aortic pressure > Ventricular pressure, so coronary arteries can be filled

Question 17

List 3 factors that can reduce the amount of time the cardiac muscle is given for perfusion (i.e. diastole time).

Answer 17

Increased HR
Increased EDV (e.g. aortic stenosis)
Valvular incompetence

Question 18

How can issues with the coronary circulation lead to increased tension on coronary vessels during exercise?

Answer 18

Work output of the heart ↑ 6-9x during strenuous exercise.
But it uses 70-80% of coronary blood flow O2 at rest (low redundancy).
Therefore, this increased demand must be met by increased flow by altering diameter of coronary vessels
–> increased tension in coronary vessels (T =PR)

Question 19

What are the 2 main control mechanisms of coronary blood flow?

Answer 19

Local metabolism - in proportion to O2 requirements of myocardium & stimulation of vasodilator release
Sympathetic stimulation - directly & via increased HR, increasing metabolic activity, but also shortening perfusion window (diastole)

Question 20

What is the effect of noradrenaline on vessels and what receptors does it act on?

Answer 20

Vasoconstriction

Alpha 1

Question 21

What is the effect of adrenaline on vessels and what receptors does it act on?

Answer 21

Vasodilation –> increased blood flow

Beta 2

Question 22

If equal amounts of noradrenaline and adrenaline were in play, what would be the overall effect?

Answer 22

Vasodilation

Question 23

&laquo_space;Why is this the case? (vasodilation overall effect)

Answer 23

Both alpha 1 and beta 2 receptors are sensitive to adrenaline, more so to the latter, so that, combined with the fact that noradrenaline dominates, means vasodilation occurs.

Question 24

&laquo_space;How then, does vasoconstriction occur?

Answer 24

Although α-receptors are less sensitive to adrenaline, when activated, they override the vasodilation mediated by β-receptors, because there are more peripheral α-1 than β-2-receptors.

Question 25

By how much does CO increase during:
Moderate exercise…
Hugely strenuous exercise…

Answer 25

3x - to 15L/min

6x - to 30L/min

Question 26

What is feedforward control when in the context of the heart, circulation and exercise?

Answer 26

Increase in CO & decrease in TPR in ANTICIPATION of activity
Through increased sympathetic & decreased parasympathetic tone

Question 27

What is also released in this feedforward mechanism?

Answer 27

ADH - in order to promote water retention and decreased urine output

Question 28

In active hyperaemia, blood flow can increase up to 20x normal. What is a knock on effect of the vasodilation that pairs with this?

Answer 28

Decrease in TPR

Question 29

Why does HR increase in whole body exercise?

Answer 29

Because blood is diverted away from non essential organs to skeletal muscle, BP can drop off, so an increase in HR is required to maintain BP in these non essential organs

Question 30

What would the effect of moderate exercise be on MABP?

Answer 30

Perhaps a small increase, but nothing major, since changes in CO & TPR would balance it out.

Question 31

What would the effect of moderate exercise be on Pulse Pressure?

Answer 31

May increase due to increased systolic as a result of increased CO and slightly decreased diastolic as a result of decreased after load due to decreased TPR

Question 32

What are the 3 factors (especially present during exercise) that increase venous return?

Answer 32

Increased skeletal muscle pump activity
Increase in frequency and depth of respiration
Increased venous tone via sympathetic innervation

Question 33

How do the physiological changes differ in static exercise than in full body mobile exercise?

Answer 33

Static: Increased venous return and occlusion of arteries and prevention of tissue perfusion, increasing TPR
Since CO also increases, result is a huge INCREASE in MABP