Physiology 9 - Exercise and Blood Flow through Special Regions Flashcards Preview

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Flashcards in Physiology 9 - Exercise and Blood Flow through Special Regions Deck (33)

When does coronary perfusion occur and why?

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


What happens if the diastole window shortens?

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


How does vasodilation of coronary arteries occur?

Build up of local factors


Which hormones/neurotransmitters contribute to vasoconstriction?



Which hormones/neurotransmitters contribute to vasodilation?



Which receptors do vasoconstriction and vasodilation use?



What happens to total peripheral resistance during dynamic exercise?

Decreases due to vasodilation occurring


What will happen to diastolic pressure during dynamic exercise?

If anything, decrease slightly


What is the pulse pressure?

Difference between systolic and diastolic pressures


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

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


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?

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


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

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


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

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


Where do the great and small cardiac veins drain to?

Coronary sinus --> RA


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

During diastole


Why is the cardiac muscle only perfused during diastole?

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


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

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


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

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)


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

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)


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

Alpha 1


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

Vasodilation --> increased blood flow
Beta 2


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



<< Why is this the case? (vasodilation overall effect)

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.


<< How then, does vasoconstriction occur?

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.


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

3x - to 15L/min
6x - to 30L/min


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

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


What is also released in this feedforward mechanism?

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


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

Decrease in TPR


Why does HR increase in whole body exercise?

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


What would the effect of moderate exercise be on MABP?

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


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

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


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

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


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

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

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