Integration Flashcards
What is the integrated view of cardiac output?
Tat CO= total tissue blood flow, which is determined by change in P/TPR
Cardiac output is dependent on ______
venous return
What determines venous return?
Right atrial presure; degree of filling (so blood volume)venous capacitance and MSFP; systemic resistance
Pa-Pv/TPR
How does venous return vary with MRAP?
As atrial pressure falls, VR increases to a point where the negative/low pressure causes vein collapse which means no further increase in VR. (diagram pg 199)
What is the mean systemic filling pressure?
The pressure when there is no flow (CO of 0), which is about 7mmHg in the RA
How does increasing blood volume of sympathetic activation alter the mean systemic filling pressure
dramatically increase the MSFP
What does altering capacitance do to the MSFP?
due to deltaP= deltaV/C, if you increase venous tone, you decrease capacitance, increasing the MSFP (infusion)
As you increase CO, the venous return is limited by _____ and the right atrial pressure _____
veins collapsing; decreases
How does vascular resistance alter the venous return curve?
Increasing the resistance will decrease the VR and vice versa (decreased resistance increases VR). DOES NOT alter the MSFP
NB e able to use overlay of CO and VR graphs to show e.g. increase in blood volume
increase in BV will increase the MSFP (by means of increasinf right atrial pressure), and the CO and VR will be greater
What happens during exercise to these two curves?
sympathetic stimulation will increase the cardiac function curve. However is TPR is not decreased (vasodilation) CO is not significantly increased. VR must be increased by the vasodilation and the muscles squeezing the veins
CO is thus determined by the heart and the vasculature
