Microcirculation and lymphatics

Question 1

What is vasomotion?

Answer 1

Intermittency of blood flow through the capillaries

Question 2

How is blood flow through the capillaries regulated?

Answer 2

Contraction and relaxation of the arterioles and precapillary sphincters

Question 3

What are factors the affect the rate of diffusion through a cell membrane?

Answer 3

Lipid solubility
Molecular size
Concentration gradient
Membrane surface area
Composition of lipid layer

Question 4

What is microcirculation?

Answer 4

Transport across the capillary wall

Question 5

What is Pc?

Answer 5

Capillary hydrostatic pressure

Question 6

What is Pi?

Answer 6

Interstitial hydrostatic pressure

Question 7

What is pi-c?

Answer 7

Capillary oncotic pressure

Question 8

What is pi-i?

Answer 8

Interstitial oncotic pressure

Question 9

What is the starling equation?

Answer 9

Fluid movement(Jv) = Kf x A [(Pc-Pi) - sigma(pi-c - pi-i)]

Question 10

What factors in the starling equation increase capillary filtration?

Answer 10

Increased Pc
Decreased Pi
Decreased pi-c
Increased pi-i

Question 11

What can increase pi-i?

Answer 11

Inadequate lymph filtration

Question 12

What can decrease pi-c?

Answer 12

Decreased protein concentration in blood

Question 13

What can increase Pc?

Answer 13

Increased arterial and venous pressure
Arteriolar dilation
Venous constriction

Question 14

What determines Kf?

Answer 14

Physical properties of the barrier

Question 15

What is sigma represent in the Starling equation?

Answer 15

Reflection coefficient

Question 16

What does is mean when the reflection coefficient is equal to 1? When it is equal to 0?

Answer 16

If sigma=1 the capillary is impermeable to protein
If sigma=0 the capillary is freely permeable to protein

Question 17

What is the net movement of fluid at the arterial end of the capillary?

Answer 17

Net outward force of 13 mmHg

Question 18

What is the net movement of fluid at the venous end of the capillary?

Answer 18

Net inward force of 7 mmHg

Question 19

What occurs when net filtration exceeds the capacity of the lymphatics?

Answer 19

Edema

Question 20

What factors prevent interstitial pulmonary edema?

Answer 20

Decreased RV force of contraction compared to LV
Increased lymph flow
Decreased interstitial oncotic pressure
High interstitial compliance

Question 21

What vasoconstrictors act on Gq receptors?

Answer 21

Norepinephrine/epinephrine
Vasopressin/ADH
Angiotensin II
Endothelin-1

Question 22

What are the steps in Gq mediated vasoconstriction?

Answer 22

Activation of Gq protein
G protein coupled activation of PLC
Phosphatidylinositol hydrolysis and formation of IP3 and DAG
IP3 mobilizes Ca++ from SR –> increased free Ca++
Ca++ binds to calmodulin which activates MLCK
Active myosin cross-bridges along actin

Question 23

What vasodilators act on Gs receptors?

Answer 23

Epinephrine
Adenosine
Prostaglandin I2 and Prostacyclin

Question 24

What vasodilators act via NO release?

Answer 24

Bradykinin
ACH
Histamine
Substance-P

Question 25

Where is autoregulation of blood flow well-developed?

Answer 25

Kidney Brain Heart Skeletal muscle Mesentery

Question 26

What is blood flow autoregulation?

Answer 26

Blood flow to an organ remains constant over a wide range of perfusion pressure

Question 27

What factors determine autoregulation in the heart?

Answer 27

Local metabolites

Question 28

What factors determine autoregulation of the brain?

Answer 28

Local metabolites - CO2

Question 29

What factors determine autoregulation in the kidneys?

Answer 29

Myogenic Tubuloglomerular feedback

Question 30

What factors determine autoregulation in the lungs?

Answer 30

Hypoxia causes vasoconstriction

Question 31

What factors determine autoregulation in the skeletal muscle?

Answer 31

Local metabolites produced during exercise Sympathetic tone at rest

Question 32

What factors determine autoregulation of the skin?

Answer 32

SyNS --> temperature control

Question 33

About how much fluid is returned to the vascular system form lymphatics a day?

Answer 33

About 3 L/day

Question 34

What is the relationship between lymph flow and interstitial fluid pressure?

Answer 34

An increase in interstitial fluid pressure will increase lymph flow

Question 35

At what interstitial fluid pressure with lymph flow plateau?

Answer 35

2 mmHg