Hemodynamics

Question 0

Resistance(R)?

Answer 0

Impediment of BF

R = (Pa-Pv)/Q

Question 1

Ohms law?

Answer 1

Q = (Pa-Pv)/R –> Q(BF) is proportional to change in pressure

CO = (MAP-RAP)/TPR
CO = MAP/TPR
*MAP = CO x TPR

Question 2

Linear velocity of Q(BF)?

Answer 2

BF velocity = 1/cross-sectional Area = 1/A (units: distance/sec)

v = Q/A

Question 3

BF is the same thru regions of vessels connected in?

Answer 3

Parallel

Question 4

BF thru regions connected in Parallel?

Answer 4

BF is the same at each level of the circulation
Total perfusion (in all systemic vascular) = CO = VR

Question 5

Bld velocity and Area relationship in the vascular system?

Answer 5

If BF is constant: bld velocity--->
							Greatest = larger vessels 
							Slowest = smaller vessels
Total Cross-sectional Area --->
							Greatest = Cap
							Smallest = Large vessels

Question 6

Explain how Poiseuilles law influences Resistance to BF?

Answer 6

Under ideal conditions the Resistance is described by poiseuilles law: Resistance is dependent on Diameter and Viscosity

R = 8nl/N(pi)r(4)

Question 7

The Hagen-Poiseuille Equation?

Answer 7

Q = [N(pi)r(4) / 8nl] x (Pa-Pv) R = 8nl/N(pi)r(4)
2r(4) = 16(Q) 1/2r(4) = 16(R)
2n = 1/2(Q) 1/2n = 2(R)
2l = 1/2(Q) 1/2l = 2(R)

Question 8

Reynolds number?

Answer 8

used to determine turbulent flow

Re = vpD/n

Re = 6000-8000 = Turbulent flow is occuring

Question 9

BF is proportional to the pressure gradient until?

Answer 9

Critical velocity is reached = murmur

Question 10

*Conductance?

Answer 10

perm. of BF C=1/R
Q = [N(pi)r(4)/8nl] x (Pa-Pv) —> double the r(4) = 16(Q)

R = 8nl/N(pi)r(4) —> halve the r(4) = 16(R)

Question 11

Resistance in Series (Rs)?

Answer 11

Rs = Change(P)/BF(=CO)
change(P): Pdiff bw before and after Rn
**Rt(s)&raquo_space; Largest Rn

Question 12

Resistance in Parallel(Rp)?

Answer 12

Rp = (Pa-Pra)/BFn = 100-0/BFn

**Rt(p) &laquo_space;Smallest Rn

Question 13

Rheological properties of Bld?

Answer 13

non-newtonian fl
viscosity calculated by Poiseuilles equation
Viscosity proportional Hematocrit

Question 14

The viscosity of bld depends on?

Answer 14

hematocrit (#Bld Cells)

Question 15

*Viscosity of bld resulting from Anemia and Polycythemia?

Answer 15

Anemia = decreases Viscosity & Resistance

Polycythemia = increases viscosity & Resistance

Question 16

The Relative Viscosity of bld and diameter?

Answer 16

Below 0.3mm: decrease Diameter = increase Viscosity

Above 0.3mm: increase Diameter = decrease Viscosity

Question 17

Plasma Skimming?

Answer 17

vessels branching at right angles = poor [RBCs]

may explain why capillary Hematocrit is 25% lower than whole bld hematocrit

Question 18

*La Place Law?

Answer 18

T = (Pi-Pt)r/w
-for a given transmural pressure (Pi-Pt):
wall tension (T) proportional radius (r)
capillary = small (r) & low (Pi-Pt) = LOW wall tension (T)
Aorta = large (r) & high (Pi-Pt) = HIGH wall tension (T)
(greater thickness & collagen)

Question 19

According to La Places Law, why are Aneurysms unstable?

Answer 19

increased (r) = increased (T) = unstable