Circulation & Hemodynamics II

Question 1

What are the components of microcirculation?

Answer 1

arterioles w/ smooth m walls

meta-arterioles w/ limited smooth m walls

capillaries w/ pre-capillary sphincters

Question 2

What moves thru clefts in capillary wall?

Answer 2

passage of water soluble substances (glucose, electrolytes)

small in brain & large in liver/gut

Question 3

What moves thru capillary endothelial cell wall?

Answer 3

lipid soluble substances (O2 & CO2)

Question 4

What is the Starling equation?

Answer 4

calculates the flow of water either out of capillary (+) or drawing it into the capillary (-)

dependent on net forces influencing movement of water

Question 5

What are the 2 forces found on both sides of capillary wall?

Answer 5

hydrostatic pressure & osmotic pressure

Question 6

Where does the fluid from gradual leakage out of capillary end up?

Answer 6

gathered by lymphatic system & returned to venous circulation

Question 7

Starling equation

Answer 7

Jv = Kf [(Pc + i) - (Pi + c)]

or

Jv= Kf [(Pc - Pi) - (c-i)]

Question 8

What does a positive Jv indicate?

Answer 8

predicts a net movement of fluid out of capillary

Question 9

What can alter these forces?

Answer 9

Pc affected by elevated venous pressure (heart failure)

Pi affected by restricted lymphatic flow or increased driving force out of capillary

c is altered by decrease in albumin (starvation, liver failure)

i is altered by restricted lymph flow or inflammation

Question 10

What is local control of circulation?

Answer 10

local beds have an ability to break from central/autonomic control if need becomes greater than is being allowed

will not usually significantly alter TPR

Question 11

Myogenic Control (autoregulation)

Answer 11

if BP is elevated, arterial walls become stretched & causes vasoconstriction

Question 12

Metabolic control

Answer 12

in active & reactive hyperemia

Question 13

Active hyperemia

Answer 13

increasing interstitial conc of metabolites (CO2, H+, K+, lactate & adenosine) or reduction of O2 b/c increasing metabolic demand

causes smooth muscle of vasc to relax & increase flow thru area

Question 14

Reactive hyperemia

Answer 14

when vascular obstruction causes build-up of metabolites & leads to vasodilation

if obstruction is removed, area will be flooded w/ blood

Question 15

Shear (method of local control)

Answer 15

if vascular bed dilates due to metabolic demand, flow thru upstream arterioles & small arteries would increase

this would increase shear (wall friction) leading to release of NO which would cause vasodilation & augment downstream metabolic effect

Question 16

Examples of neural & hormonal control of blood flow

Answer 16

sympathetics
histamine & bradykinin
serotonin
prostaglandin

Question 17

Effect of sympathetics

Answer 17

vasoconstriction (if decreased stimulation=vasodilation)

Question 18

Effect of histamine & bradykinin

Answer 18

arteriolar vasodilation

increases Kf (allowing escape of large molecules)

causes edema in response to tissue damage

Question 19

Effect of serotonin

Answer 19

vasoconstriction in response to tissue damage

Question 20

Effect of prostaglanin

Answer 20

mixed!

Question 21

Coronary Circulation

Answer 21

LARGELY metabolic control

LV contraction causes constriction of vasculature (near endocardial surface)

Question 22

Cerebral Circulation

Answer 22

largely metabolic control (responds to increase CO2)

Question 23

Pulmonary Pressure

Answer 23

avg pressure is up to 20 in pulmonary A (highest pressure of pulm vascular system in RV & pulm A)

Question 24

What is the resistance of the pulmonary vasculature compared to systemic circulation?

Answer 24

lower resistance (about 1/10)

Question 25

Regulation of Pulmonary Blood Flow

Answer 25

vasoconstriction to alveolar hypoxia so directs blood to areas receiving O2

little sympathetic influence

Question 26

How do pulmonary arteries differ from systemic?

Answer 26

arterial system of lungs is more compliant so small changes in mean pressure will significantly dilate arteries

reduces resistance & helps maintain low pressure even w/ large changes in flow

Question 27

Skeletal Muscle Circulation

Answer 27

@ rest-under central baroreceptor control

when active-comes under local control

Question 28

How are adrenal glands involved in flight response?

Answer 28

secrete epi which bind B2 receptors & causes vasodilation

Question 29

How does BP stay constant when skeletal m is active?

Answer 29

motor centers cause generalized increases in sympathetic outflow so increased CO & non-muscular vascular resistance to anticipate drop in TPR from skeletal m dilation

Question 30

Skin Circulation

Answer 30

sympathetic vasoconstriction from baroreceptor reflex

sympathetic inhibition & dilation of shunt pathways to release excessive body temperature

Question 31

What is a right to left shunt?

Answer 31

blood passing from systemic veins to systemic arteries w/o passing thru functional lung tissue

Question 32

What is a left to right shunt?

Answer 32

blood passing from systemic arteries to systemic veins w/o passing thru capillary bed for substance exchange

Question 33

Where is sympathetic innervation of vascular smooth muscle the highest?

Answer 33

highest in skin & skeletal muscle vasculature!

Question 34

What is Pc?

Answer 34

pressure inside capillary that favors filtration OUT of capillary (decreases along length of capillary so lowest Pc @ venous end)

Question 35

What is Pi?

Answer 35

pressure of interstitial fluid that opposes filtration (moving of fluid from IF to capillary)

Question 36

What is pie c?

Answer 36

capillary oncotic pressure (due to plasma proteins)

increase in protein conc of blood will decrease filtration

Question 37

What is pie i?

Answer 37

interstitial oncotic pressure that favors filtration (dependent on protein conc of interstitial fluid)