Lecture 11+12 Flashcards
What is MSFP and what is it affected by?
represents the average equilibrated pressure throughout systemic circulation without blood flow
this creates the pressure gradient that allows for blood flow into the right atrium
MSFP can be affected by blood volume and venous resistance
What factors affect venous return
MSFP
RAP
arteriole resistance
blood volume
venomotor tone
arteriolar tone
body posture, muscle pump, and respiratory pump in regards to VR?
increased BV increases VR, decreased BV decreases VR
body posture = more venous pooling and lower VR
muscle pump = increases VR
respiratory pump: increases VR
venoconstriction vs VR
arterial vasoconstriction vs VR
venoconstriction= increases VR
arterial vasoconstriction = lower VR
arterial vasodilation = higher VR
The vascular function curve
As the RAP increases the VR will decrease
heart usually operates at RAP = +2 at VR = 5 L/min
What factors impact the vascular function curve
- blood volume
decreased blood volume will shift line down and to the left; MSFP is decreased
increased blood volume will shift line up and to the right; MSFP is increased - venoconstriction
shifts the line to the right and upward; MSFP is increased - venodilation
shifts the line to the left and down; MSFP is decreased - arteriolar resistance
vasodilation = shift graph up (increased VR); no change in MSFP
vasoconstriction- shift graph down; no MSFP change
What factors regulate CO?
- pumping ability of the heart (HR)
mainly in control during stress - venous return (SV)
mainly in control if CO during rest
Cardiac function curve
the higher the RAP the higher the CO
increased VR = increased EDV = increased CO
What factors affect the cardiac function curve
increasing contractility will increase CO
vice vera
decreasing afterload will increase CO
vice versa
Guyton Cross plot
the combination of the CFC and VFC
where the lines intersect is steady state
What factors affect the guyton cross plot
higher contractility will shift the CFC upward and to the left; the VFC is not affected ( high CO and low RAP)
low contractility will shift CFC down and right; VFC not affected
hemorrhage will alter the VFC and not the CPC
increased BV = higher CO
decreased BV = lower CO
increased TPR:
will shift the CPC down and shifts the VFC down
(decreased CO, decreased VR, no change in RAP)
Decreased TPR:
will shift CPC and VFC upward.
(increased CO, VR, and no change in RAP)
Digoxin and guyton cross plot
CO curve is shifted up and to the left
VF curve is not changed
CO will increase and RAP will decrease
cardiac failure decreases contractility
CO is low and RAP is high
Digoxin is used to prevent heart failure
Effect of exercise
will increased contractility and venoconstriction
What is the RMP in cardiocytes
-90 mV
Phases of an AP of a typical ventricular myocyte
Phase 0: rapid depolarization (threshold is -70)
opening of fast Na channels
phase 1: initial rapid repolarization
Na inactivation and outflow of K (transient outward K channels)
Phase 2: plateau phase
opening of L-type calcium channels (Ca into cell)
Phase 3: rapid repolarization
Due to outward K current through delayed rectifier channels
Phase 4: resting phase
Na and Ca channels are closed
small K current
