15. Hemodynamics & Systemic Circulation

Question 1

what is the pressure in the As after the aorta

Answer 1

highest

= stressed volume

Question 2

what is the pressure in arterioles compared to As

Answer 2

moderate P

Question 3

where in the circulatory system can you change resistance to control flow

Answer 3

arterioles

Sm M contract to control flow by changing resistance

Question 4

what determines ther degree of perfusion in capillaries

Answer 4

constriction/dilation of arterioles

Question 5

what is the P in venules

Answer 5

low P

(large vol)

Question 6

how can venules control BP

Answer 6

contract to move more blood to arteries to increase BP

Question 7

what are characteristics of Vs

Answer 7

large capacitance

low P, large vol = unstressed vol

Question 8

what are characterisitccs of capillaries

Answer 8

lare cross-sectional area

single endothelial lining

nutrient/waste/gas exchange

Question 9

what area of circulation has to largest area

Answer 9

capillaries

Question 10

where is blood volume least

Answer 10

aorta/As/arterioles

Question 11

relative to the parts of circulation, what is the area and BV of the Vs

Answer 11

large A (but smaller than capillaries)

large BV

Question 12

how does area contribute to velocity of blood flow

Answer 12

inverse relationship (increase A –> decrease velocity)

V = Q/A

(calculated single vessel or total summed cross sectional A of parallel circuits)

Question 13

compare the velocity of the aorta & capillaries

Answer 13

aorta - high velocity ( bc small area)

capillaries - low velocity ( bc large crossectional A)

Question 14

what is the flow from aorta to systems

Answer 14

flow is consistent, however the flow is divided btn the systemsl like ….

cerebral = 15%, coronary = 5 %, etc

Question 15

how does flow change throughout the system

Answer 15

the percent division btn systems change based on hormones/activity

like… exercise - more blood sent to MSK than GI

*- based on arteriole resistance*

Question 16

how does pressure gradient and resistance contribute to flow

Answer 16

flow (Q) = pressure gradient/R

pressure gradient directly related to flow

R inversely related to flow

Question 17

how do you calculate cardiac output with pressure and resistance

Answer 17

=(arterial pressure - venous pressure) / total peripheral resistance

(=pressure gradient/R)

Question 18

how is Resistance calculated

Answer 18

change R w/

1. viscosity - direct relationship
2. length of vessel - direct relationship
3. * vessel radius * = most significant & inverse relationship

Question 19

how is vessel radius controlled & what is the purpose

Answer 19

hormones or local factors

change resistance to regulate BP and match blood flow to metabolic needs

Question 20

how do you calculate vascular resistance for vessels in series

Answer 20

add the resistances

(longer the tube - more resistance)

Question 21

how do you calculate vascular resistance for vessels in parallel

Answer 21

1/R(total) = 1/R1 + 1/R2 + etc

total resistance decrease

Question 22

when does laminar flow change to turbulent flow

Answer 22

high velocity

large cross sectional area

heavy density or

low viscosity

>2000 Reynolds number (=transition)

Question 23

how does you calculate reynolds number

Answer 23

increases w/ density, diameter, velocity

decrease with viscosity

Question 24

what can turbulent flow lead to

Answer 24

sound (bruits)

lesion (arteriosclerosis)

Question 25

what is laminar flow

Answer 25

high velocity in middle & zero on the walls (bc increased viscosity on walls) ideally = parabolic

Question 26

what is complaince

Answer 26

how easy it is for a vessel to expand (--\> holds more volume) change in vol/change in pressure

Question 27

what has a larger compliance Vs or As

Answer 27

Vs easiest to stretch --\> so hold larger volume at lower pressure

Question 28

what is the compliance for As

Answer 28

low harder to expand --\> so need larger P to hold low volumes

Question 29

what happens to compliance when Sm. M of Vs contract

Answer 29

decrease compliance --\> decrease volume (shift volume from V to A) so in A increase P and volume

Question 30

what happens to complaince with aging As

Answer 30

walls get stiffer --\> decrease compliance so you need higher Ps to hold same amount of volume

Question 31

why do you have pulsatile pressure in aorta

Answer 31

compliance and distension during ejection and recoild during diastole -lost by arterioles

Question 32

what is the pulse pressure dependent on

Answer 32

atrial compliance

Question 33

why is the pulsitile pressure higher in the large As compared to the aorta

Answer 33

echo effect -waves bouncing back fron small As and arterioles

Question 34

where is pulsatile pressure lost

Answer 34

arterioles

Question 35

what happens to P in the arterioles

Answer 35

huge decrease bc high resistance to flow at end around 30 mm HG

Question 36

how is systolic pressure and diastolic pressure reported clinically

Answer 36

systolic = greatest P in large A diastolic = lowest P in large A

Question 37

why is mean pressure closer to diastolic P

Answer 37

spend more time in diastole than systole = diastolic + 1/3\*pulse

Question 38

how do you calculated pulse pressure

Answer 38

systolic - diastolic

Question 39

what happens if you have a decrease in compliance of arterials

Answer 39

increase pulse P -increased systolic P & diastolic stays same (but could decrease)

Question 40

what happens to pulse P in arteriosclerosis

Answer 40

decrease compliance increase pulse P

Question 41

what happens to pulse P in aortic stenosis

Answer 41

decrease pulse pressure bc decreased SV

Question 42

what happens to the pulse pressure (and its graph) if R is increased

Answer 42

shift the entire graph up \*no change in shape\*

Question 43

What is the clinical significance of an increased left atrial pressure?

Answer 43

indicative of heart failure or decreased left ventricular output

Question 44

What is the pulmonary wedge pressure directly proportional to?

Answer 44

left atrial pressure