Vascular Control

Question 1

what can be used to measure fluid overload? what determines it?

Answer 1

preload

determined by volume in the central venous compartment

Question 2

where are the venous reserves stored? what is the other component of the venous system?

Answer 2

the peripheral venous compartment

other compartment is the central venous compartment

Question 3

what is the main variable that is controlled by the arterioles in circulation?

Answer 3

they determine intravascular resistance

Question 4

what is contained within the central venous compartment?

Answer 4

the vena cavae and the right ventricle

Question 5

what determines preload and afterload?

Answer 5

preload determined by volume in the central venous compartment and the afterload is determined by the resistance in the arterioles

Question 6

where would most of the blood go if the heart was not beating?

Answer 6

to the peripheral venous system

Question 7

what are two ways to determine central venous pressure?

Answer 7

looking at jugular venous distension or by putting a central venous catheter in the internal jugular vein that measures the pressure at the cavoatrial junction

Question 8

what is an assumption that can be made about the central venous pressure compared to the right atrial pressure?

Answer 8

they are approximately equal

Question 9

what changes the central venous pressure? what affect does it have on the heart beat?

Answer 9

a change in volume within that compartment

an increase in venous pressure increases stroke volume and therefore cardiac output

Question 10

describe the venous function curve

Answer 10

relates venous return to central venous pressure. when CVP increases, venous return decreases

Question 11

why does venous return decrease when central venous pressure increase?

Answer 11

because the driving force from the periphery is pressure, so the closer that the CVP gets to peripheral pressure, the less flow that occurs

Question 12

what happens to the venous function curve when volume is decreased? why?

Answer 12

the curve shifts to the left because there is less peripheral venous pressure driving flow and therefore there must be less central venous pressure to allow the same amount of flow

Question 13

what happens to the mean arterial pressure when the heart is stopped? what is this called?

Answer 13

the MAP becomes 7 mmHg and this is called the mean systemic filling pressure

Question 14

why is there residual pressure in the vasculature when the heart stops beating?

Answer 14

it is a result of the pressure exerted by the volume of blood in the system itself

Question 15

what happens to the mean systemic filling pressure when the blood volume is increased or decreased?

Answer 15

when decreased, the mean systemic filling pressure decreases. when the blood volume increases, it decreases.

Question 16

what two factors may shift the venous function curve?

Answer 16

a change in blood volume or venous tone

Question 17

what two factors contribute to the cardiac output of the heart?

Answer 17

the venous function curve and the cardiac function curve

Question 18

what occurs when venous return does not match the intersection of cardiac function and the venous function curve?

Answer 18

the central venous pressure is increased and there is a lowering of venous return to come back to equilibrium

Question 19

what is a typical central venous pressure?

Answer 19

2 mmHg

Question 20

without increasing venous function, what is the result of increasing sympathetic nerve activity to the heart?

Answer 20

the heart has increased contractility and there is an increased venous return and increased cardiac output

Question 21

how does the body work to correct the leftward shift of the venous return graph to increase cardiac output when there is hemorrhage?

Answer 21

venous constriction mobilizes more venous reserve volume to effectively increase volume (and shift the curve back to the right a little) while sympathetic activation increases cardiac contractility

Question 22

what is the result of resetting the cardiac output of the system after hemorrhage?

Answer 22

the cardiac output and venous return returns to normal but there must be a decreased central venous pressure to accommodate this

Question 23

what would cause a right shift of the cardiac function curve and what would this result in?

Answer 23

heart failure

this would result in a shift of equilibrium towards and increased central venous pressure

Question 24

what produces a plateau in the vascular function curve at negative central venous pressure?

Answer 24

partial venous collapse

Question 25

what occurs with increase flow in the heart?

Answer 25

decreases central venous pressure because it shifts blood from the venous to the arterial side

Question 26

how does increased blood volume lead to a rightward shift of the venous function graph?

Answer 26

because increase in volume leads to an increased pressure in the peripheral venous system which is the driving force of venous return. the dilation of the vessels that results also decreases their resistance to flow

Question 27

why does a change in vasoconstriction of the arterioles result in the same mean systemic filling pressure?

Answer 27

because the blood volume has not changed and the amount of blood within the arterioles is relatively small

Question 28

how does an increase in arteriolar tone result in a decrease of venous return?

Answer 28

increased resistance decreases the amount of bloodflow to the peripheral venous system and therefore decreases the peripheral venous pressure