# Poiseuille's Law

1. Jan 7, 2010

### sameeralord

Ok first of all before I get to this I have one question,

What does loss of hydrosatic pressure due to resistance mean in this equation. What happens to the molecules when they lose hydrostatic pressure, do they stop moving and accumulate?

Poiseuille's Law says that if you decrease the diameter there is less flow? My question is the dimater is decreased the speed of the particles increase? Can't this counteract the less volume entering the tube and create the same flow?

If there is low flow. Let's say in artery why does increasing heart rate increase flow?
Is the reason behind this?

A----------------------------------B ( o mh/hg)
(Heart increase pressure at point A to 200 mg/hg)

Does this create a higher pressure difference and a higher flow? If hydrostatic pressure is acting perpendicular to the surface how can it push molecules in a horizontal direction?

Also when you just start to pump blood to an artery and point A has flow pumped and B still hasn't? Wouldn't B be compressed due to atmospheric pressure outside?

Also when a blood vessel is dilated?

-----------------------------<(o mg/hg)
A-100 mg/hg

If the point of flow is to maintain 100 mg/hg everywhere around the tube, why does hydrostatic pressure inside a dilated tube increase? I mean when it reached 100 mg/hg doesn't the flow stop? How is equilibrum reached here?