L25 Systemic Circulation II

Question 1

Compliance of large arteries and veins

Answer 1

Veins = most compliant

Large arteries = least compliant

As pressure gets higher , volume gets higher

All eventually reach elastic limit

Once high volumes reached , vein and artery compliance become fairly similar

Question 2

Venous pressure gradient

Answer 2

Low pressures <10mmHg

High capacitance 70% blood

Pressure gradient from capillaries to right atrium
Important because required to get blood back to heart

Small changes in pressure can have serious physiological ramifications

Question 3

Blood in venous circulation can be described as

Answer 3

Unstressed volume

Because pressures are low

Question 4

Blood in arterial circulation is considered

Answer 4

Stressed volume

Because pressures are high

Question 5

Changes in venomotor tone will alter amount of

Answer 5

Unstressed blood

Increased venomotor tone = decrease venous compliance = less unstressed volume (Q transferred to arterial side)

Decreased venomotor tone = increase venous compliance = more unstressed volume (Q accumulates in veins)

Venomotor tone is outflow to veins causing contraction of smooth muscle

Question 6

Cardiac output is the determinant of

Answer 6

How much blood arrives at cells doorstep /right atrium

Question 7

Venous return is all

Answer 7

The blood , loaded with CO2, arriving at the heart to be pumped once again

Question 8

Venous return and cardiac output must be

Answer 8

Balanced

Cannot be separated

Varying one must affect the other side

Question 9

CV model

Answer 9

Predict cardiovascular behavior based on physical properties of pump (heart) and plumbing (vasculature)

Question 10

Right atrial pressure

Answer 10

Key variable in CV models

CO depends on preload, which is a function of RAP

Increase RAP, increase EDV, increase CO
Decrease RAP, decrease EDV, decrease CO

RAP also determines driving force for atrial filling (requires delta P = Pv - RAP)

Increase RAP, decrease atrial filling, decrease VR
decrease RAP, increase atrial filling, increase VR

Question 11

Cardiac function curve

Answer 11

Depicts relationship btw EDV (proportional to RAP) and CO

Translated to relationship btw CO and RAP

Question 12

Venous (vascular) function curve

Answer 12

Relationship btw VR and RAP

Increase RAP , decrease VR

VR=0 , maximal RAP - mean systemic pressure ( no delta P)

Question 13

Mean systemic pressure

Answer 13

Can be measured anywhere when the heart is stopped and blood volume equalizes in all vascular spaces

~7mmHg

Only depends upon:
Total blood volume and
Vessel compliance

Represents anchor for vascular function curve

Question 14

Combined cardiac and vascular function curves

Answer 14

Line intersection is only RAP where CO and VR are equal

Unique operating or equilibrium point of system in steady state

Question 15

Inotropicity effects on cardiac/vascular function curves : increasing

Answer 15

Increasing cardiac inotropicity (digitalis)

Increased contractility, SV, CO

RAP decreases because more blood ejects from heart on each beat (shifted upward and left)

Vascular function curve not affected

Question 16

Inotropicity effects on cardiac/vascular function curves : decreasing

Answer 16

Decreasing cardiac inotropicity

Decreased contractility, SV, CO
RAP increased because less blood ejected from heart on each beat (shifted down and right)

Vascular function curve not affected

Question 17

Blood volume Effects on cardiac/vascular function curves: increasing

Answer 17

Increasing blood volume (transfusion)

Increased mean systemic pressure, CO, RAP

similar response if venous compliance is decreased (venoconstriction, decrease unstressed volume, Q shifted from venous to arterial vessels)

Vascular function curve shifted to right

Question 18

Blood volume Effects on cardiac/vascular function curves: decreasing

Answer 18

Decreasing blood volume (blood loss)

Decreased mean systemic pressure, CO, RAP

similar if venous compliance is increased (increase venodilation, increase unstressed volume)

Vascular function curve to left

Question 19

Total peripheral resistance increase effects on cardiac/vascular function curves

Answer 19

Increasing TPR by vasoconstricting

Increased volume in arteries, increased afterload on heart

Depressed CO (cardiac function curve shifts downward)

vascular function curve shifts downward because less blood returning to heart (greater proportion is trapped in the arteries)