Blood Flow

Question 1

Hemorrheology

Answer 1

Flow of blood through circulatory system

Question 2

Structure of BV

Answer 2

All (except capillaries) contain elastic fibers, SmM, collagen
 Tunica intima = inner endothelial layer, smooth surface to prevent clotting (all BV)
 Tunica media = SmM, elastic connective tissue
 Tunica externa = adventitia, fibrous collagen fibers

Question 3

Blood: Fluid Type?

Answer 3

Blood: non-Newtonian fluid, delivered through progressively narrowing blood vessels in pulsatile non-linear or even turbulent manner

Major factors in blood flow resistance = Blood viscosity

Question 4

Vascular Hindrance

Answer 4

Represents resistance to physiologic blood flow, Rp

Resistive forces = viscosity x impedance

Question 5

Viscosity of Blood

Answer 5

primarily dependent on [RBC] (HCT), RBC deformability, RBC aggregability, plasma viscosity, temp, blood flow conditions

Question 6

Shear Stress

Answer 6

force applied during pulsatile blood flow btw theoretical layers of blood in blood vessel

Question 7

Shear-Rate

Answer 7

principal determinant of NO concentration, increases as viscosity decrease s as large arteries become smaller = greatest in capillaries regardless of flow rates

Relates to Fahreaeus-Linquist Effect

Question 8

Glycocalyx

Answer 8

Carbohydrate-rich layer composed to negatively charged network of proteoglycans, glycoproteins, glycolipids lining vascular endothelium t/o capillaries, arteries, veins

Important role in maintaining vascular wall homeostasis by regulating blood flow, RBC/WBC movement, vessel wall permeability in capillaries
 Pathologic loss: breakdown of vascular barrier = ischemia, SIRS, sepsis, vol overload

Question 9

Colloid Oncotic Pressure and the Glycocalyx

Answer 9

Replaces interstitial colloid osmotic pressure of proteins as a determinant of fluid flux across capillary

 Plasma proteins (albumin) escape to interstitial space via intracellular clefts: responsible for increased fluid flux across capillary during inflammation

Question 10

Factors that cause fluid accumulation in interstitial spaces

Answer 10

1. Increased filtration coefficient DT histamine, cytokines
2. Increased capillary pressure DT volume overload, venous obstruction, heart failure
3. Decreased capillary oncotic pressure from hypoproteinemis

Question 11

Decreased Contractility/Decreased Ventricular Systolic Function

Answer 11

neonates/juveniles/peds, DCM, secondary CMs, inhalants, propofol, hypocalcemia, acidosis, beta blockers

Question 12

Decreased Preload/Decreased Ventricular Systolic Function

Answer 12

low total body water (geriatrics), dehydration, third spacing (ascites, effusions, etc), hemorrhage, hypovolemia, vascular occlusion/compression, PPV, VD

Question 13

Impedance

Answer 13

relationship btw pulsatile pressure, pulsatile flow in arteries

sum of pulsatile resistive components (Rp), non-pulsatile resistive (R) components of longitudinal arterial resistance

Frequency dependent, not time dependent

Question 14

Ventricular-Vascular Coupling

Answer 14

Ideal: decrease systolic arterial pressure (lowest myocardial work), increase diastolic (adequate perfusion of heart, peripheral tissues)

Increases in arterial stiffness: increase pulse pressure amplitude, systolic pressure; decrease diastolic
 Consequences: increase myocardial work, increase oxygen consumption, increase energy requirements, decrease myocardial perfusion

Question 15

Cardiac Compliance

Answer 15

SV/aortic pulse pressure

Question 16

Frank Starling Mechanism

Answer 16

relationship btw EDV and systolic ventricular performance (force or pressure development)
* Monofilaments increase sensitivity to Ca = increase contractile force

Question 17

Afterload

Answer 17

Forces that resist ejection of blood into aorta, closely related to tension (stress) in ventricular wall during systole
 Tension (stress) developed by L vent wall during ejection OR as arterial input impedance
 Force, tension developed before ventricle ejects

Afterload = vascular resistance, reactance (stiffness)

Question 18

Four Phase of Diastole

Answer 18

 Isovolumic relaxation
 Early rapid filling
 Slow ventricular filling (diastasis)
 Atrial systole (during sinus rhythm)

Question 19

Bowditch Effect/Treppe Effect

Answer 19

Increased HR = rate-dependent accumulation of cytosolic Ca2+