PSIO 532 Study Guide - Midterm Guide: Blood Vessel, Foldit, Viscosity
Graduate Physiology PSL
Poiseuille’s La
➔ Explai ho Poiseuille’s La ifluees resistae to flo. Use it to alulate hages i
resistae i a rigid tue lood essel. Explai the deiatios fro Poiseuille’s la
predictions that occur in distensible blood vessels
Poiseuille’s Euation – The factors that determine the resistance of a blood vessel to
blood flow are expressed by the Poiseuille Equation:
The important concepts expressed in the Poiseuille Equation are as follows:
▪ First, esistance to flo is diectly popotional to iscosity η of the
blood; for example, as viscosity increases (e.g., if the hematocrit
increases), the resistance to flow also increases
▪ Second, resistance to flow is directly proportional to the length (l) of the
blood vessel (there is more resistance the longer the blood goes through
the tube, or vessel)
▪ Third, and most important, resistance to flow is inversely proportional
to the fourth power of the radius (r4) of the blood vessel
This demonstrates how powerful the relationship is i.e. when
radius decreases, resistance increases, not linearly, but by the
fourth power.
For example, if the radius of a blood vessel increases by one half,
resistance does not simply decrease two fold—it decreases by 16-
fold
Overall, the higher the radius, the LOWER the resistance
θ Use the original resistance equation (R = P/Q) and
oie it ith Pouseuille’s La
θ This will tell us how pressure and flow are related
to the fators of Pouseuille’s La
θ The pressure difference across a blood vessel is
diectly popotional to the length and iscosity η of
the blood
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Document Summary
Explai(cid:374) ho(cid:449) poiseuille"s la(cid:449) i(cid:374)flue(cid:374)(cid:272)es resista(cid:374)(cid:272)e to flo(cid:449). Use it to (cid:272)al(cid:272)ulate (cid:272)ha(cid:374)ges i(cid:374) resista(cid:374)(cid:272)e i(cid:374) a rigid tu(cid:271)e (cid:894)(cid:271)lood (cid:448)essel(cid:895). Explai(cid:374) the de(cid:448)iatio(cid:374)s fro(cid:373) poiseuille"s la(cid:449) predictions that occur in distensible blood vessels. Poiseuille"s e(cid:395)uation the factors that determine the resistance of a blood vessel to blood flow are expressed by the poiseuille equation: Third, and most important, resistance to flow is inversely proportional to the fourth power of the radius (r4) of the blood vessel. This demonstrates how powerful the relationship is i. e. when radius decreases, resistance increases, not linearly, but by the fourth power. For example, if the radius of a blood vessel increases by one half, resistance does not simply decrease two fold it decreases by 16- fold. Overall, the higher the radius, the lower the resistance. Use the original resistance equation (r = p/q) and (cid:272)o(cid:373)(cid:271)i(cid:374)e it (cid:449)ith pouseuille"s la(cid:449)
