1,2- Overview of Circulation and Hemodynamics

Question 1

arteries

Answer 1

for high pressure to transport to organs

Question 2

arterioles

Answer 2

for controls and distribution of flow

Question 3

capillaries

Answer 3

to exchange nutrients, electrolytes, hormones, etc.

have the largest overall cross sectional area, in parallel with one another. blood moves the slowest here so you have time for exchange of nutrients/O2 and CO2

Question 4

venules

Answer 4

to collect blood from the capillaries

Question 5

veins

Answer 5

to transport of blood back to heart

Question 6

Order of systemic circulation

Answer 6

arteries -> arterioles -> capillaries -> venules -> veins

Question 7

are pulmonary and systemic circulation in series or parallel?

Answer 7

series but within each are parallel elements so blood is distributed to various vascular beds independently depending on what the tissues needs are. also means that disruption in blood supply to one part of circulation doesnt mean it will disrupt everywhere

Question 8

is arterial or venous pressure higher?

Answer 8

arterial but most of the blood is in the veins (venous side is more compliant)

100ml of blood is what makes the arterial pressure

Question 9

explain the pulsatile nature of the heart

Answer 9

pressure is most pulsatile near the “pulsing” heart. you have the largest pressure drop at the arterioles. Pressure overall drops as blood moves from arterial to venous sides of circulation and pressure becomes less pulsatile.

Question 10

bloodflow in an individual vessel segment is determined by

Answer 10

inflow-outflow pressure

Question 11

relationship between pressure/flow/resistance

Answer 11

change in pressure = flow x resistance

flow is always in the direction from high to low pressure

Question 12

blood pressure

Answer 12

bp = force exerted by blood / area of vessel wall

Question 13

Conductance

Answer 13

measure of blood flow through a vessel for a given pressure difference. Simply the inverse of resistance

1/Resistance

C~d^4 (varies in proportion of the 4th power of diameter)

Question 14

Poiseuille’s Law

Answer 14

F= (deltaP) (Pi) r^4/ 8 (viscosity)(length)

Note: vessel radius plays greatest role in determining rate of blood flow through a vessel

Question 15

Ohms law with respect to the heart

Answer 15

F = (deltaP) / R

Question 16

laminar flow

Answer 16

steady state flow streamlines

Question 17

hematocrit

Answer 17

% of cells in blood, pressure must go up to surpass viscosity factor

normal men ~42%
normal women ~38%
anemia < normal
polycythemia > normal

Question 18

Calculate resistance in series and parallel

Answer 18

series-> add them and the total is greater than the largest

parallel-> add 1/each R together and the total is less than the smallest

Question 19

systolic vs. diastolic pressure

Answer 19

systolic pressure- each time the heart beats it ejects blood which increases arterial bp to peak

diastolic pressure- as vessels empty, blood moves from arteries to veins the pressure falls

Question 20

pulse pressure

Answer 20

systolic pressure - diastolic pressure

Question 21

how to increase systolic pressure

Answer 21

goes up if vessels get stiffer and harder

Question 22

how to increase diastolic pressure

Answer 22

goes up if you have an elevated HR

Question 23

arterial pressure contours

Answer 23

• stroke volume ejected into arterial tree (how much blood is pumped out of heart)
• force of contraction/how hard heart is pumping (determines peak systole)
• heart rate determines time of diastolic runoff (longer time between beats the greater the runoff of the ejected volume into the venous circulation, and therefore the lower the diastolic pressure)
• arterial vascular resistance (a greater resistance reduces the runoff of blood into the veins before the next beat and therefore diastolic pressure is high)

Question 24

what happens during aortic regurgitation

Answer 24

ejected stroke volume flows back inot the ventricle (regurgitation) during diastole; with an A-V shunt blood flows directly into the venous circulation. Both lower diastolic pressure.

Question 25

what happens to a pressure vs time curve when you have arteriosclerosis

Answer 25

arteriosclerosis- stiffining of aorta

the graph just gets taller

Question 26

what happens to the pressure vs time curve when you have aortic stenosis

Answer 26

stenosis- valve doesnt open all the way (closure of the aortic ring)

LV pressure is very high here and the graph becomes much shorter and flatter

Question 27

what happens to the pressure vs time curve when you have patent ductus arteriosus

Answer 27

low R for blood to come back out of aorta (high systolic and low diastolic pressure)

graph gets taller and the little step near the top moves further down

Question 28

what happens to the pressure vs time curve when you have aortic regurgitation

Answer 28

it becomes a tall hill without any little step near the systolic pressure top

Question 29

mean arterial pressure

Answer 29

average of all pressures integrated and averaged over time

approximately equal to DBP + 1/3 Pulse

Question 30

how do veins work

Answer 30

can constrict and dilate, thus serving important blood storage function

venous “muscle pumps” propels blood foward to return blood to heart (smooth muscle)

Question 31

what determines pressure in veins

Answer 31

right atrial pressure- regulated by balance between ability of right heart to pump out blood and the tendency for blood to flow from the peripheral veins into the right atrium

*heart is responsible for setting final lowest pressure in venous pressure (if it can’t then you have edema)

Question 32

blood reservoirs

Answer 32

venous side of circulation plays “blood storage role”

spleen
liver
large abdominal veins
venous plexus of skin
heart 
lungs

Question 33

factors that tend to collapse veins entering thorax

Answer 33

1. large veins have little resistance
2. veins that enter thorax are compressed at certain points so flow is impeded
3. intrathoracic pressure is negative which distends veins and atmospheric pressure collapses neck veins
4. abdominal veins are compressed by organs and intra-abdominal pressures

Question 34

gravitational/hydrostatic pressure

Answer 34

weight of blood in column causes greater pressure in the longer column of fluid cause of gravity

blood doesnt normally balloon out of veins b/c smooth muscle (skeletal muscle kinda does) contracts to squeeze it back to the heart. Veins are distensible so they can get larger and larger

gravitational pressure = density of blood x acceleration due to gravity (980) x vertical distance above or below heart

Question 35

why is it bad to stand absolutely still for 15 mins-ish

Answer 35

with no leg movement, elevated pressure in legs raises capillary pressure (fluid filters out) and the leg swells

you can lose 10-20% of blood volume in 15 mins w/o moving