BIOC34H3 Lecture Notes - Lecture 8: Vascular Resistance, Sympathetic Nervous System, Blood Vessel
19 Mar 2019
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Lecture 8: blood flow continued and the fetal heart: blood flow continued. Blood flow (bf) = change in pressure ( p)/resistance (r) We can calculate resistance (r) to blood flow along a blood vessel using poiseuille"s law: r = 8l / In this equation, r is resistance, l is blood vessel length, is viscosity and r is radius. By looking at this equation, we can see that if viscosity increases, resistance increases. If the pressure gradient remains constant then blood flow will decrease. If the radius of the vessel increases, then resistance decreases. If pressure remains constant then blood flow will increase. Given that radius is to the fourth power in this equation, it exerts large an effect on resistance. Doubling the radius reduces the resistance to 1/16th its original level, whilst flow is increased 16 times. Poiseuille"s law holds true for a single blood vessel.
