Question 1

Which of the following best describes the function of the circulatory system in multicellular organisms?

Accepted Answer

It links exchange surfaces with cells throughout the body, facilitating the transport of gases, nutrients, and hormones.

Question 2

In an open circulatory system, what is the name of the fluid that circulates, and where does chemical exchange primarily occur?

Accepted Answer

Hemolymph; in the sinuses surrounding organs

Question 3

Which of the following is a major disadvantage of single circulation, as seen in fish?

Accepted Answer

Blood pressure drops significantly after passing through the gill capillaries, limiting efficient delivery to body tissues.

Question 4

During the cardiac cycle, what causes the 'lub' sound heard in a heartbeat?

Accepted Answer

The closing of the atrioventricular (AV) valves due to blood recoiling against them

Question 5

Which equation correctly represents cardiac output ($$CO) in $$terms of heart rate ($$HR) $$and stroke volume ($$SV$$)?

Accepted Answer

$$CO = HR 	imes SV$$

Question 6

Why does blood flow slow down as it enters capillaries, despite capillaries being narrower than arteries?

Accepted Answer

The total cross-sectional area of all capillaries is much greater than that of arteries, reducing velocity.

Question 7

Which blood vessel type contains valves to prevent backflow, and why is this necessary?

Accepted Answer

Veins; to ensure unidirectional blood flow at low pressure

Question 8

What is the primary mechanism for movement of fluid out of capillaries into surrounding tissues?

Accepted Answer

Blood pressure at the arterial end of the capillary

Question 9

Which component of blood is most directly responsible for transporting oxygen?

Accepted Answer

Erythrocytes containing hemoglobin

Question 10

A patient has a heart murmur. Which of the following best explains the cause of this condition?

Accepted Answer

Blood squirts backwards through a defective valve, causing abnormal sounds.

Question 11

Which of the following statements about gas exchange is correct?

Accepted Answer

Gas exchange is the uptake of molecular O2 from the environment and discharge of CO2 to the environment.

Question 12

Calculate the partial pressure of CO2 in the atmosphere if its concentration is 0.04% and atmospheric pressure is 760 mm Hg. Use $$P_{CO_2$} = 	ext{fraction} 	imes 	ext{total pressure}.$$

Accepted Answer

$$P_{CO_2$} = 0.0004 	imes 760 = 0.304 	ext{ mm Hg}$$

Question 13

Which adaptation allows birds to breathe efficiently at high altitudes?

Accepted Answer

They inhale fresh air with every breath, preventing mixing of oxygen-rich and oxygen-poor air.

Question 14

What is the tidal volume of a human at rest?

Accepted Answer

500 mL

Question 15

Which of the following best explains why not all air is exhaled from the lungs during forced exhalation?

Accepted Answer

Residual volume ensures mixing of fresh air with oxygen-depleted air, keeping alveolar partial pressure of O2 lower than atmospheric.

Question 16

Which respiratory pigment is found in diving mammals and allows them to store oxygen in muscle tissue?

Accepted Answer

Myoglobin

Question 17

Which process is responsible for the formation of fibrin threads during blood clotting?

Accepted Answer

An enzymatic cascade leads to the formation of thrombin, which converts fibrinogen to fibrin.

Question 18

Which of the following is true about capillaries in the human body?

Accepted Answer

Only 5-10% of capillaries have blood flowing through them at any given time.

Question 19

A patient’s ECG shows abnormal electrical impulses. Which structure is most likely malfunctioning?

Accepted Answer

Sinoatrial (SA) node

Circulation and Gas Exchange: Structure, Function, and Adaptations

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