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.)
-In the image shown, a simplified cardiovascular system is modeled as an electrical circuit. Which of the following would occur if the blood flow to the brain is blocked? (Assume that the blood pressure supplied by the heart remains unchanged.)

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.)
-In the image shown, a simplified cardiovascular system is modeled as an electrical circuit. Which of the following would occur if the blood flow to the brain is blocked? (Assume that the blood pressure supplied by the heart remains unchanged.)

Quizplus · Accepted Answer

11ecba2d_12c5_0843_a3bf_87b35aca88c3_MD0008_00 The three biological components (resistors) shown in this model make a parallel circuit, and the heart (battery) generates the pressure difference (voltage) that drives blood flow (current). The properties of parallel resistors are: The voltage drop across each resistor is the same. If they are in parallel with the battery, the voltage drop across each resistor will be equal to that of the voltage generated by the battery. The equivalent resistance decreases if a resistor is added in parallel. Conversely, the equivalent resistance increases if a resistor in parallel is removed. The current through each resistor is independent from that through the other resistors. The total current is equal to the sum of the currents through each component. From the analogous properties, the equivalent resistance (total vascular flow resistance) will increase with the removal of a resistor (the brain) because it is in parallel with the other components. (Choice B) The voltage drop across each resistor will be equal to that of the battery, which does not change. (Choice C) The current through each resistor in a parallel circuit is related only to the intrinsic resistance of the resistor and the electric potential (voltage). Vascular resistance of the gut and systemic blood pressure both remain constant after obstructing blood flow to the brain, so blood flow through the gut does not change. (Choice D) If this were a series circuit in which the current flows through only one path, all flow would stop by blocking one element. Parallel circuits have more than one path through which current can flow. Educational objective: For resistors in parallel, the voltage drop across each resistor is the same. The equivalent resistance increases if a resistor is removed. The current through each resistor in parallel is independent from the others, and the sum of each component current equals the total current.

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