Flashcards in deck_628720 Deck (23):
What does more metabolic activity lead to?
What does a fall in arterial pressure do?
-- increase flow resistance to certain tissues (skin, gut)-- venoconstriction
What occurs when you eat a meal?
Local vasodilation --> TPR fallsIncrease in venous pressure (increase CO)Decrease in arterial pressure (increase HR & CO)Increasing CO --> decreases venour pressure and increases arterial pressure --> demand is met --> system is stable
What is "muscle pumping"?
Muscle action forces extra blood back to the heart
What happens when the heart rate increases but nothing else changes?
initially cardiac output will tend to rise, but TPR is the sameIncreased CO --> decreased venous pressure --> decreased stroke volume --> CO back to normal ** heart rate is driven by the circulation**
How is the huge demand increase during exercise met?
Large decrease in the TPR so there is a surge of blood back to the heart (increased venous pressure)
What are the things that must be coped with during exercise?
venous pressure increases greatlyarterial pressure falls greatly-- can be too big to cope with
Which of the changes in exercise is the bigger problem?
Increased venous pressure-- tends to overfill the heart-- ventricle is pushed onto flat portion of Starling curve
How do you match the left and right ventricle?
Beat at the same rate so have to match the stroke volume (relies on Starling curve)
What is there a risk of developing if the right and left ventricular stroke volumes do not match?
Pulmonary oedema-- is RH pumps more, L fills more and pumps more-- when on top of Starling curve, L cannot respond, so blood will accumulate in the lungs --> pulmonary oedema
How is overfilling of the ventricles prevented in exercise?
By increasing the heart rate as you begin exercise-- is driven by the brain-- lower stroke rate is needed when the increase blood volume arrives in the heart
What happens when you stand up?Why are deep veins not affected?
Blood pols in superficial vein the the legs due to gravity-- causes central venous pressure to fallDeeper veins are surrounded by water in tissues, as there is less pressure difference
What happens to CO when you stand up?
CO falls--> arterial pressure falls--> arterial and venous pressure are both falling-- cannot be corrected by normal mechanisms
How are pressure changes combatted when you stand up?
Baroreceptors detect fall in AP --> raise HR-- TPR increases to defend the arterial pressure 1. divert blood away from skin and gut to the brain to prevent fainting 2. movement after standing pumps blood in veins to restore blood flow3. central venous pressure increases to get more blood into the heart
What is the condition that occurs when the mechanisms to restore normal pressure do not work upon standing?
What are the changes in circulation that occur during haemorrhage?
Reduced blood volume will decrease venous pressure-- causes CO and arterial pressure to fall-- heart rate increases after detection by baroreceptors which increases TPR
Why is an increase heart rate detrimental in haemorrhage?
Increase HR removes more blood from veins which lowers the venous pressure, decreases heart filling and lowers stroke volume. Causes a weak and rapid pulse. Pale as diverting blood to brain
What are the control mechanisms for haemorrhage?
Increase venous pressure1. veno-constriction (contract smooth muscles in walls) to increase stroke volume2. "auto-transfustion" - replaces blood volume lost-- short term method-- increase blood fluid by drawing it from the extracellular space
What organ controls the volume of the blood?Describe the relationship between blood volume and venous pressure
kidneys -- increase blood volume, increase venous pressure
What occurs when you increase the blood volume over a long period of time?
venous pressure increasesCo increasesArterial pressure rises -- more blood forced through tissues --> increases TPR --> increasing AP more which then remains high
What controls mean blood pressure?In which illness are these important?
Blood volume control mechanisms e.g. kidneysHypertension
What is the arterial pressure determined by?
Blood volume in the arteries