Question 1

Which of the following best explains why erythrocytes (red blood cells) have a biconcave shape?

Accepted Answer

It increases the cell's surface area to volume ratio, enhancing gas exchange efficiency.

Question 2

A patient is exposed to carbon monoxide (CO). Which of the following best explains why CO poisoning is so dangerous?

Accepted Answer

CO binds to hemoglobin with a much higher affinity than O$$_2$$, preventing oxygen transport.

Question 3

Which of the following equations correctly represents cardiac output (CO)?

Accepted Answer

$$CO = HR 	imes SV$$

Question 4

During vigorous exercise, the partial pressure of oxygen ($$P_{O_2$}) in $$muscle tissue decreases. According to the oxygen-hemoglobin dissociation curve, what happens to hemoglobin saturation in these tissues?

Accepted Answer

Hemoglobin saturation decreases, allowing more oxygen to be released to the tissues.

Question 5

Which of the following best describes the chloride shift in red blood cells?

Accepted Answer

It exchanges bicarbonate ions ($$HCO_3$$^-$$) out of the cell for chloride ions (Cl$$^-$$) into the cell to maintain electrical neutrality during CO_2$ transport.

Question 6

A woman with type O negative blood is pregnant with a fetus who is Rh positive. Which condition is she at risk for in subsequent pregnancies, and why?

Accepted Answer

Hemolytic disease of the newborn, because she may develop anti-Rh antibodies that attack fetal RBCs.

Question 7

Which of the following best describes the sequence of excitation in the cardiac conduction system?

Accepted Answer

SA node → AV node → Bundle of His → Bundle branches → Purkinje fibers

Question 8

Which of the following is a direct effect of sympathetic stimulation on the heart?

Accepted Answer

Increased heart rate due to enhanced pacemaker activity at the SA node.

Question 9

Which of the following best explains why veins have valves but arteries do not?

Accepted Answer

Valves in veins prevent backflow of blood due to lower pressure and help return blood to the heart against gravity.

Question 10

Which of the following hormones increases blood pressure by promoting sodium and water retention in the kidneys?

Accepted Answer

Aldosterone

Question 11

A patient stands up quickly from a lying position and feels dizzy. Which physiological mechanism is primarily responsible for restoring blood pressure in this situation?

Accepted Answer

Baroreceptor reflex increases sympathetic output, causing vasoconstriction and increased heart rate.

Question 12

Which of the following is the correct pathway of blood flow through the heart, starting from the right atrium?

Accepted Answer

Right atrium → Right ventricle → Pulmonary artery → Lungs → Pulmonary vein → Left atrium → Left ventricle → Aorta

Question 13

Which of the following best describes the role of arterioles in the circulatory system?

Accepted Answer

They regulate blood flow and pressure by constricting or dilating, earning the name 'resistance vessels.'

Question 14

Which of the following is a product of heme breakdown after red blood cell destruction?

Accepted Answer

Bilirubin

Question 15

Which of the following best describes the function of carbonic anhydrase in red blood cells?

Accepted Answer

It catalyzes the conversion of CO$$_2$$ and H$$_2O to H$_2CO$_3 ($$carbonic acid), facilitating CO$$_2$$ transport.

Question 16

Which of the following statements about the layers of the heart wall is correct?

Accepted Answer

The myocardium is the thickest layer and is responsible for the heart's contractile force.

Question 17

Which of the following best describes the difference between arteries and veins?

Accepted Answer

Arteries have thicker walls and more smooth muscle to withstand higher pressure, while veins have thinner walls and valves to prevent backflow.

Question 18

Which of the following is the main determinant of blood pressure that is directly measured by a sphygmomanometer?

Accepted Answer

Mean arterial pressure (MAP)

Question 19

Which of the following best explains why the largest reservoir of blood is found in the veins?

Accepted Answer

Veins have a large lumen and high compliance, allowing them to store more blood at lower pressure.

Question 20

Which of the following is a correct statement about the phases of the cardiac cycle?

Accepted Answer

During ventricular systole, the AV valves are closed and the semilunar valves are open.

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