The Effect Of Fluid Shifts On Cardiovascular Responses

2902 Words Aug 15th, 2014 12 Pages
Effects of Fluid Shifts on Cardiovascular Responses
Introduction
In the human body, the flow of blood through vessels is determined by pressure differentials and vascular resistance. There a number of feedback systems which are responsible for the regulation of arterial pressure, dependent on autonomic nerves and circulating hormones. Moreover, depending on the region of the body the vascular resistance is influenced by; level of sympathetic vasomotor nerves, levels of hormones and local factors including metabolites and endothelial factors. Additionally, resistance is dependent on the length of vessel and inversely with diameter; larger driving force equals faster flow, and increasing resistance hinders flow. The equation below conveys the relationship between pressure, resistance and flow.
Flow = Pressure ÷ Resistance
The main factors determining blood flow resistance are; 1) viscosity of blood; 2) length of conducting tube and; 3) radius vessel. The equation below represents Poiseuille’s law articulating the interaction between pressure gradient, resistance, and flow in a cylindrical vessel.
Flow = Pressure Gradient x Vessel Radius ÷ Vessel Length x Fluid Viscosity
The viscosity of blood along a vessel remains almost constant. Therefore, the radius of the vessel is the most important factor in relation to affecting the blood flow. If the radius of the vessel was to be halved, the flow would be decreased by 16-fold; and, doubling the radius increases the volume by a factor…
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