Question 1

Which of the following best explains why multicellular animals require a circulatory system, while most unicellular organisms do not?

Accepted Answer

Multicellular animals have specialized cells that cannot directly exchange materials with the environment due to increased diffusion distances.

Question 2

In an open circulatory system, such as that found in insects, which of the following statements is correct?

Accepted Answer

Hemolymph directly bathes the organs and there is no distinction between blood and interstitial fluid.

Question 3

Which of the following equations correctly describes the relationship between diffusion time ($$t) $$and distance ($$x) $$for molecules in biological systems?

Accepted Answer

$$t \propto x^2$

Question 4

Which of the following is a key advantage of a closed circulatory system over an open circulatory system?

Accepted Answer

It maintains higher pressure, allowing more efficient transport of nutrients and gases to tissues.

Question 5

Which of the following best describes the path of blood flow in the mammalian double circulatory system?

Accepted Answer

Right ventricle → pulmonary artery → lungs → pulmonary vein → left atrium → left ventricle → aorta → body → vena cava → right atrium

Question 6

A patient has a heart rate of 80 beats per minute and a stroke volume of 75 mL per beat. What is their cardiac output in liters per minute? Use the formula $$CO = HR 	imes SV.$$

Accepted Answer

$$6.0 L/$$min

Question 7

Which of the following statements about the mammalian heart valves is correct?

Accepted Answer

The atrioventricular (AV) valves prevent backflow of blood from the ventricles to the atria during ventricular contraction.

Question 8

Which of the following best explains why blood velocity is slowest in capillaries?

Accepted Answer

The total cross-sectional area of capillaries is much greater than that of arteries or veins.

Question 9

Which of the following is a function of the lymphatic system?

Accepted Answer

Returning excess interstitial fluid to the bloodstream and playing a role in immune defense.

Question 10

Which of the following would most likely result from a malfunction of the left atrioventricular (mitral) valve?

Accepted Answer

Backflow of blood from the left ventricle to the left atrium during ventricular contraction.

Question 11

Which of the following best describes the role of the sinoatrial (SA) node in the heart?

Accepted Answer

It acts as the pacemaker, initiating the electrical impulses that set the rate and timing of cardiac muscle contraction.

Question 12

Which of the following is a correct statement about the regulation of blood pressure?

Accepted Answer

Vasoconstriction increases blood pressure by reducing the diameter of arterioles.

Question 13

A person with a high LDL to HDL ratio is at increased risk for which of the following conditions?

Accepted Answer

Atherosclerosis and cardiovascular disease

Question 14

Which of the following best explains why giraffes have a much higher systolic blood pressure than humans?

Accepted Answer

They need to pump blood a greater distance against gravity to reach the brain.

Question 15

Which of the following is the correct sequence of events in the formation of a blood clot?

Accepted Answer

Vasoconstriction → Platelet plug formation → Coagulation (fibrin mesh formation)

Question 16

Which of the following best describes the main function of erythropoietin (EPO) in the body?

Accepted Answer

It stimulates the production of red blood cells in response to low oxygen levels.

Question 17

Which of the following is a correct description of the difference between arteries and veins?

Accepted Answer

Arteries carry blood away from the heart, while veins carry blood toward the heart.

Question 18

Which of the following best explains why blood pressure is measured at the level of the heart?

Accepted Answer

To minimize the effects of gravity on the measurement.

Question 19

Which of the following is a likely consequence of a thrombus forming in a coronary artery?

Accepted Answer

A heart attack (myocardial infarction) due to blocked blood flow to cardiac muscle.

lecture 2 Circulatory Systems in Animals: Structure, Function, and Regulation

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