Passage
In hemodynamics, blood flow through the cardiovascular system can be modeled as an electric circuit in which the blood serves as electricity, the blood vessels as resistive wires, and the heart as a battery (see Figure 1) .
Figure 1 Cardiovascular circuit modelOhm's law states that the voltage drop ΔV across each element, the current I flowing through it, and its electrical resistance R are related by ΔV = IR. In a blood vessel, pressure difference between one vessel and the next ΔP replaces ΔV, volumetric blood flow Q replaces I, and vascular resistance R replaces electrical resistance. Therefore, Ohm's law for blood flow in a vessel isΔP = QREquation 1Vascular resistance is due to the blood's viscosity η and the dimensions of the vessel through which it flows. Assuming blood vessels are cylinders, R can be approximated as
Equation 2where L is the length of the vessel, and r is its inner radius. If Equation 2 is combined with Equation 1, the resulting equation is Poiseuille law.In a study of the circulatory system in rats, researchers measured the intravascular blood pressure of the mesenteric blood vessels. The mesentery is the set of tissues that holds the intestines in place. Blood flows in the following order: aorta, superior mesenteric artery (SMA) , arterial arcade, venous arcade, superior mesenteric vein (SMV) .For the procedure, catheters with pressure transducers were inserted into each vessel via laparotomy. Laparotomy is an invasive procedure that involves a surgical incision into the abdominal cavity. Blood pressure measurements were taken simultaneously at the proximal end (beginning) of each blood vessel.
Figure 2 Mesenteric blood pressure profile of rats (Note: SMA = superior mesenteric artery; SMV = superior mesenteric vein.)
-The blood pressures of an artery in the neck and in the leg of a person lying down are measured, and their difference calculated. When the blood pressures are taken after the person stands up, their difference:

Question

Passage
In hemodynamics, blood flow through the cardiovascular system can be modeled as an electric circuit in which the blood serves as electricity, the blood vessels as resistive wires, and the heart as a battery (see Figure 1) .

Figure 1 Cardiovascular circuit modelOhm's law states that the voltage drop ΔV across each element, the current I flowing through it, and its electrical resistance R are related by ΔV = IR. In a blood vessel, pressure difference between one vessel and the next ΔP replaces ΔV, volumetric blood flow Q replaces I, and vascular resistance R replaces electrical resistance. Therefore, Ohm's law for blood flow in a vessel isΔP = QREquation 1Vascular resistance is due to the blood's viscosity η and the dimensions of the vessel through which it flows. Assuming blood vessels are cylinders, R can be approximated as

Equation 2where L is the length of the vessel, and r is its inner radius. If Equation 2 is combined with Equation 1, the resulting equation is Poiseuille law.In a study of the circulatory system in rats, researchers measured the intravascular blood pressure of the mesenteric blood vessels. The mesentery is the set of tissues that holds the intestines in place. Blood flows in the following order: aorta, superior mesenteric artery (SMA) , arterial arcade, venous arcade, superior mesenteric vein (SMV) .For the procedure, catheters with pressure transducers were inserted into each vessel via laparotomy. Laparotomy is an invasive procedure that involves a surgical incision into the abdominal cavity. Blood pressure measurements were taken simultaneously at the proximal end (beginning) of each blood vessel.

Figure 2 Mesenteric blood pressure profile of rats (Note: SMA = superior mesenteric artery; SMV = superior mesenteric vein.)
-The blood pressures of an artery in the neck and in the leg of a person lying down are measured, and their difference calculated. When the blood pressures are taken after the person stands up, their difference:

Quizplus · Accepted Answer

11ecba2d_12c4_9311_a3bf_bd1aa754a073_MD0008_00 The pressure exerted by the weight (potential energy) of a fluid is directly proportional to its depth. This pressure is known as hydrostatic pressure. The hydrostatic pressure difference ΔP between any two points in a fluid is found by ΔP = ρgΔh where ρ is the density of the fluid, g is the acceleration due to gravity, and Δh is the vertical displacement between the locations where the initial and final pressures are measured. When the person is lying down, the neck and the leg are at about the same height level, making Δh negligible. However, when the person stands up, the Δh between the neck and the leg increases significantly. The blood pressure difference increases due to the hydrostatic pressure of the column of blood from above the leg to below the neck. (Choice A) From Equation 2, flow resistance is due to the viscosity of blood and the geometry of the vessel. Flow resistance is independent of the direction of flow. (Choice B) An ideal fluid is one which possesses negligible viscosity. Blood is not modeled here as an ideal fluid. In addition, an ideal fluid would still experience hydrostatic pressure. (Choice C) Viscosity is a measure of a fluid's resistance to flow due to internal frictional forces; it is not a measure of pressure. In addition, viscosity acts in the direction opposite of the flow. Educational objective: Hydrostatic pressure is the pressure exerted by the weight (potential energy) of a fluid. The hydrostatic pressure difference between two points in a fluid is proportional to the fluid's density, the gravitational acceleration, and the vertical displacement between the two points.

Passage In Hemodynamics, Blood Flow Through the Cardiovascular System Can Be