Session 6 Flashcards
Describe response of CVS due to a haemorrhage
Loss of blood so venous pressure falls Cardiac output falls So arterial pressure falls Baroreceptors detect the fall in arterial and so heart rate increases to try and increase arterial pressure TPR increases Rise in heart rate lowers venous pressure further Venous pressure needs to be increased Venoconstriction Blood transfusion to replace lost volume Cold, pale, skin Heart rate high, weak pulse
Describe the response of the CVS to a long term increase in blood volume
Blood under control of kidney Increase in venous pressure Drives blood back to heart Cardiac output rises Arterial pressure rises Elevates blood pressure More blood perfuses tissues which auto regulate and increase TPR Wash away metabolised Contract more Arterial pressure rises further and stays up --> determined by blood volume we have WEEKS MONTHS
What effect does an increase in heart rate have on venous pressure?
Lowers
Describe the response of the CVS to standing up
Blood pools to legs due to gravity
Venous pressure falls
Cardiac output falls
Arterial pressure falls
Cannot be corrected by normal mechanisms
Baroreceptors detect and increase heart rate
TPR increased to defend arterial pressure
Describe the response of cvs to postural hypotension
Sometimes reflexes don’t work upon standing
Occurs more as people get old
Hypotension drugs reduce volume of blood
Problem is the reduction of venous return
Extra pressure on veins is needed
Blood should be returned to heart but instead remains in the legs
Describe response of CVS to exercise
Increase in demand
Muscles force blood back to heart
Usually there would be overfilling but this is prevented by an increase in heart rate in response to exercise
When venous pressure rises, heart rate is already high
Stroke volume kept low but cardiac output increases
Demand is met so stable
Describe what would happen if exercise wasn’t under control
Overfilling of ventricles
Arterial pressure fall
Venous pressure rise
Starlings curve flat part
Pulmonary oedema because left cant meet demand of right due to starlings law so blood accumulates in lung
More blood enter than removed so blood accumulate in spaces between lungs
How does a rise in venous pressure affect cardiac output?
Increases
How does a fall in arterial pressure effect heart rate and cardiac output?
Increases
How does extra pumping of heart effect venous pressure and arterial pressure?
Reduce venous
Increase arterial
Describe the response of the cvs to eating a meal
Increase in metabolites and therefore local vasodilation
TPR falls -> arterial pressure fall -> venous pressure rise
Rise in cardiac output
Rise in heart rate and cardiac output
Reduction in venous pressure and increase in arterial pressure due to extra pumping
System stable
What does a fall in arterial pressure do?
Increases flow resistance to certain tissues
Venoconstriction
Emergency mechanism
Brain can’t cope but skin and gut can for example
What does an increase in heart rate with no other change cause?
Cardiac output rise TPR stay same Venous pressure reduced Stroke volume reduced Cardiac output returns to normal Heart cannot drive the circulation, its driven by it.
