Physio Test 3: Hemodynamics & Microcirculation

Front 1

microcirculation

Back 1

small vessels embedded in organs that distribute blood within tissues

Front 2

macrocirculation

Back 2

larger vessels that carry blood to/from organs

Front 3

Resistance vessels

Back 3

small arteries/arterioles

Front 4

characteristics of resistance vessels

Back 4

have thicker walls (relative to larger arteries) with more smooth muscle. Major regulators of flow and SVR

Front 5

terminal arterioles

Back 5

smaller arterioles that give rise to caps

Front 6

terminal arteriole characteristics

Back 6

exhibit vasomotion (spontaneous contraction/dilation); only 1/3 are usually open at rest; more can be recruited if oxygen needs increase

Front 7

exchange vessels

Back 7

capillaries, postcapillary nonmuscular veins, terminal lymphatic capillaries

Front 8

exchange vessel characteristics

Back 8

walls are a single endothelial layer on basement membrane; permeability varies depending on tightness of cell junctions, fenestrations.

Front 9

capacitance vessels

Back 9

muscular venules, small veins

Front 10

capacitance vessel characteristics

Back 10

greater diameter than arteries, so contain more blood. This is a major blood reservoir that is mobilized via neural/hormonal factors to affect venous return

Front 11

parenchymal cells

Back 11

surrounding tissue cells that release vasodilator metabolites to affect VSM contraction

Front 12

main targets of autonomic innervation

Back 12

resistance vessels, terminal arterioles, capacitance vessels, sympathetic adrenergic constrictors.

Front 13

distribution of sympathetic innervation w/in microcirculation

Back 13

sparse in areas that are not constricted much (heart, lungs, brain). more dense in skin, skeletal muscle, kidney.

Front 14

endothelial cells

Back 14

tonic release of local autacoid dilators, which affect VSM, leukocytes, platelets. control capillary permeability

Front 15

determinants of flow to tissues

Back 15

flow is proportional to perfusion pressure and radius. Radius is most important.

Front 16

autoregulation

Back 16

tendency to keep flow constant, despite fluctuations in arterial pressure. without neural/hormonal control.

Front 17

myogenic control

Back 17

arterial smooth muscle contracts when pressure increases, relaxes when pressure decreases, in order to maintain steady flow. Contraction depends on stretch-activated calcium channels. **venous does not do this

Front 18

metabolic control

Back 18

depends on local release of vasodilator metabolites by parenchymal cells in proportion to metabolic rate and oxygen availability.

Front 19

metabolic ctl example

Back 19

increase in arterial pressure >> increases flow >> lower concentration of dilators (washed out quicker) >> constriction >> increases resistance >> return flow to lower level.

Front 20

active hyperemia

Back 20

changing concentration of vasodilators in proportion to change in metabolic rate. increasing activity >> more vasodilators released >> dilate nearby resistance vessels >> increases blood flow

Front 21

autacoids

Back 21

local tissue hormones released by vascular/parenchymal cells that act on VSM.

Front 22

histamine

Back 22

released by mast cells; dilator that increases capillary permeability

Front 23

bradykinin, prostaglandins, leukotrienes

Back 23

dilators

Front 24

thromboxanes and serotonin

Back 24

constrictors

Front 25

NO, prostacyclin, endothelin

Back 25

from endothelial cells; NO/prostacyclin are dilators, endothelin is constrictor.

Front 26

sympathetic constrictor nerves

Back 26

tonically active, releasing NE to alpha AR to constrict smooth muscle. Generates neurogenic tone that controls SVR, MAP

Front 27

sympathetic dilator nerves

Back 27

only in resistance vessels in skeletal muscle. activated early in exercise, make endothelial cells release NO.

Front 28

adrenal medullary catecholamines - NE

Back 28

NE binds alpha AR on VSM, increase SVR and decrease CPL of veins. Raise MAP

Front 29

adrenal medullary catecholamines - E

Back 29

binds beta 2 AR on VSM in skeletal, coronary muscle, opposes constriction. Dilates.

Front 30

extrinsic vs local control

Back 30

extrinsic look to maintain MAP at expense of regional flow; Local looks to match perfusion to metabolic needs and autoregulate.

Front 31

diffusion

Back 31

rapid, accounts for majority of capillary exchange. depends on concentration gradient, permeability of capillary wall, surface area of capillary

Front 32

surface area

Back 32

determined by tone. decreasing tone increases SA and diffusion

Front 33

ultrafiltration

Back 33

bulk flow; transcapillary movement of water and dissolved solute in response to hydrostatic and osmotic pressure gradients across cap wall.

Front 34

capillary hydrostatic pressure

Back 34

pressure w/in capillary, pushing fluid out; drops from arterial to venous end based on how much resistance is present.

Front 35

plasma osmotic pressure

Back 35

large plasma proteins favors holding water in capillary

Front 36

Kf

Back 36

filtration constant; permeability of capillary

Front 37

what does vasoconstriction of arterioles do to pressure in capillary

Back 37

lowers pressure at arteriole end of capillary (due to greater resistance), so there is less of a gradient pushing water out and less filtration

Front 38

vasodilation of arterioles and pressure in caps

Back 38

increases pressure at arteriole end (less resistance) so more of a gradient pushing water out, more filtration. Increases CVP

Front 39

Increase in CVP and pressure in caps

Back 39

increases pressure in caps, net filtration; risk of edema.

Front 40

Flow =

Back 40

pressure drop / resistance

Front 41

series resistance

Back 41

change in resistance in one segment will produce a proportional change in total resistance of circuit

Front 42

parallel resistance

Back 42

change in resistance in one branch will have little effect on total resistance of circuit.

Front 43

velocity

Back 43

speed with which blood moves past a specific point. inversely related to XS area.

Front 44

velocity is fastest in

Back 44

aorta, b/c it has the least surface area overall

Front 45

velocity is slowest in

Back 45

capillary beds, b/c it has a very large aggregate area

Front 46

resistance is highest

Back 46

in arterioes, due to small diameter. Pressure drop is also the greatest here.

Front 47

turbulence favored by

Back 47

low viscosity, large vessel, high velocity

Front 48

effects of turbulence

Back 48

pressure drop decreases flow and increases AL (heart must work harder);

Front 49

tension is proportional to

Back 49

Pressure and radius of a vessel.

Front 50

chronic HTN and tension

Back 50

increases tension, so arteries develop thicker walls to counteract it.

Front 51

pulse pressure

Back 51

difference in systolic and diastolic

Front 52

MAP =

Back 52

1/3 systolic = 2/3 diastolic

Front 53

SV and systolic pressure

Back 53

increasing SV increases Systolic pressure

Front 54

CPL and systolic pressure

Back 54

decreasing CPL increases systolic

Front 55

SVR and diastolic pressure

Back 55

increasing SVR increases Diastolic

Front 56

CPL and diastolic

Back 56

decreasing CPL decreases diastolic b/c less expansion during systole means less recoil during diastole

Front 57

HR and pulse pressure

Back 57

increasing HR increases pulse pressure (increases Systolic and decreases diastolic)

Front 58

compliance

Back 58

wall distensibility of a vessel. equals change in volume over change in pressure

Front 59

CPL in arteries vs veins

Back 59

veins more compliant than arteries b/c they are usually less full. can accommodate larger change in volume w/ little change in pressure.

Front 60

Sympathoexcitation and CPL

Back 60

contraction of venous VSM decreases compliance, speeds venous return to heart

Front 61

CPL and CVP

Back 61

decreasing CPL increases CVP

Front 62

dilating arterioles and CVP

Back 62

dilating arterioles increases pressure in caps, increases venous pressure and return.

Front 63

CO and CVP

Back 63

decreasing CO increases CVP b/c blood gets backed up behind heart