please help! understanding resistance: decreasing or increas

[sohel2009]

hello, i am new here and really glad to know that there is a forum for discussion for talking about medical issues..
btw, my quick question is...i am quiet confuse about the effects of resistance on arterial pressure..

i have read some books: Ganong's physiology, Guyton's medical physiology, Lauralee sherwood's physiology books. and i found that :

1. in one part, all of the books said that the high resistance (high viscosity, long vessel length and small radius of the vessel) would decrease the arterial pressure ,so that there would be a pressure gradient to allow the fluid to flow..(because of this reason, i understand why there is a drop in MAP in the arterioles)
2. but i found in the other part, that the arteries vasoconstriction ( which means that the vessels radius is becoming smaller) will elevate the MAP..

i am quiet confuse understanding this contradictions

..please someone help me to understand...
warm regards,

[pulle998]

I'm not exactly sure, but I think the question is whether all the factors in combination (vasoconstriction/dilation, viscosity, vessel cross sectional area, length, ect.) function to decrease or increase the velocity of the blood. Velocity varies inversely with pressure or MAP in this case.