Question 1

Which of the following best explains why blood flow increases as the diameter of a blood vessel increases, according to Poiseuille’s Law?

Accepted Answer

Resistance is inversely proportional to the fourth power of the vessel radius: $$R = \frac{1}{r^4$}$$

Question 2

A patient has a blood clot that increases the viscosity of their blood. According to Poiseuille’s Law, what effect will this have on blood flow?

Accepted Answer

Blood flow will decrease because resistance is proportional to viscosity: $$R \propto \eta$$

Question 3

Which of the following statements about the cardiac cycle is correct?

Accepted Answer

Systole refers to the contraction phase, while diastole refers to the relaxation phase

Question 4

During which phase of the myocardial contractile cell action potential does calcium influx primarily occur, and what is its effect?

Accepted Answer

Phase 2 (plateau); maintains depolarization and allows sustained muscle contraction

Question 5

Which of the following best describes the function of AV (atrioventricular) valves in the heart?

Accepted Answer

They prevent blood from flowing backward into the atria when the ventricles contract

Question 6

A patient’s mean arterial pressure (MAP) is calculated using the following formula: $$MAP = CO 	imes PR. If $$cardiac output (CO) increases and peripheral resistance (PR) remains constant, what happens to MAP?

Accepted Answer

MAP increases

Question 7

Which of the following is a unique property of autorhythmic (pacemaker) cells compared to contractile myocardial cells?

Accepted Answer

Autorhythmic cells have unstable membrane potentials called pacemaker potentials

Question 8

Which of the following best describes the effect of vasoconstriction on blood pressure and flow?

Accepted Answer

Vasoconstriction decreases vessel diameter, increasing resistance and blood pressure

Question 9

Which of the following is true regarding the flow of blood through the heart?

Accepted Answer

Blood flows from the right atrium to the right ventricle, then to the pulmonary arteries

Question 10

Which of the following best explains why capillaries are the primary site of exchange between blood and tissues?

Accepted Answer

Capillaries have thin walls and a large surface area, allowing efficient exchange

Question 11

If the pressure gradient across a blood vessel doubles, what happens to the flow rate, assuming resistance remains constant?

Accepted Answer

Flow rate doubles: $$Flow = \frac{\Delta P}{R}$$

Question 12

Which of the following is a direct result of the opening of voltage-gated L-type Ca$$^{2+}$$ channels in cardiac muscle cells?

Accepted Answer

Calcium enters the cell, triggering further Ca$$^{2+}$$ release from the sarcoplasmic reticulum

Question 13

Which of the following best describes the role of gap junctions in cardiac muscle?

Accepted Answer

They allow electrical signals to pass rapidly between cells, enabling coordinated contraction

Question 14

A patient’s ECG shows a prolonged QRS complex. What does this most likely indicate?

Accepted Answer

Delayed ventricular depolarization

Question 15

Which of the following is true regarding the refractory period in cardiac muscle cells?

Accepted Answer

It prevents sustained (tetanic) contractions, allowing the heart to relax between beats

Question 16

Which of the following would most likely result in an increase in peripheral resistance?

Accepted Answer

Decreased vessel diameter due to vasoconstriction

Question 17

Which of the following best describes the function of semilunar valves?

Accepted Answer

They prevent blood from flowing back into the ventricles from the arteries

Question 18

Which of the following is a consequence of increased blood viscosity?

Accepted Answer

Increased resistance and decreased blood flow

Question 19

Which of the following is true regarding the relationship between blood flow, pressure gradient, and resistance?

Accepted Answer

Blood flow is directly proportional to the pressure gradient and inversely proportional to resistance: $$Flow = \frac{\Delta P}{R}$$

Cardiovascular Physiology: Heart Structure, Blood Flow, and Cellular Mechanisms

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