Cardiac phys concepts

[Dr. X]

since many of us use BRS phys and FA.. im running across some confusion which i would like to clear up. i consider phys my weakest.. :(

1) brs states (pg. 70):
cardiac output = (MAP - Right Atrial pressure)/TPR

FA states (formula section): MAP = CO/TPR

(i wonder who's gonna say.. most likely it won't show up on the exam)

2) pg. 71 of 4th edition brs phys:

Laminar flow vs. turbulent flow:

Increase in ******** number means turbulence (audible bruits) and it is seen in:

Decreased blood viscosity (decreased hematocrit, anemia)
Increased blood velocity (eg. narrowing of a vessel)

I agree with the above except for the "narrowing of a vessel" part.
let me jus post the formulas so its easy to work through it.

a) Q = MAP-RAP/TPR
b) R = 8nl/pie r^4
c) V = Q/A

with formula b, Narrowing of a vessel means decrease in radius would cause an increase the resistance. (inverse relationship) (side note: decreased resistance means decreased viscosity as in "decreased hematocrit and anemia")

with formula a, Increase in resistance would mean Decrease in Cardiac output (Q) (inverse relationship)

with formula c, decrease in cardiac output means decrease in velocity (direct proportional relationship)...

which conflicts with the bottom bold statement. so should it be "dilation of the vessel" or am i jus missing something in btw..

[Dr. X]

i wrote r e y n o l d s number and it gave me the **********.

[dskuri2001]

Could someone explain the concept of contractility?
By definition it states that it is the intrinsic ability of a heart muscle fiber to contract at a given fiber length. And that anything that can't be explained by the notion of preload is defined as contractility. I understand the concept of preload but what are the specific parameters that can't be explained by preload.

[FedeUBA]

MAP=CO/TPR is wrong!!!!
the correct formula is: MAP=COXTPR

[madeeha khan]

MAP=COXTPR
given in FA 2006 page 218