$$CO = 80 \times 75 = 6000 mL/$$min

Question 1

Which of the following best describes the main advantage of a countercurrent exchange system in fish gills?

Accepted Answer

It maintains a large partial pressure difference of $$O_2$$ across the entire gill surface, increasing diffusion efficiency.

Question 2

Which equation correctly calculates cardiac output ($$CO) in $$humans?

Accepted Answer

$$CO = HR 	imes SV$$

Question 3

A patient has a stroke volume ($$SV) of 80 mL/$$beat and a heart rate ($$HR) of 75 $$beats/min. What is their cardiac output ($$CO$$)?

Accepted Answer

$$CO = 80 	imes 75 = 6000 mL/$$min

Question 4

Which of the following is NOT a function of capillaries in the circulatory system?

Accepted Answer

Generating high pressure to move blood through arteries

Question 5

Why are open circulatory systems most suitable for sedentary or slow-moving organisms?

Accepted Answer

They allow direct contact of hemolymph with tissues, which is sufficient for low oxygen demands.

Question 6

Which of the following statements about the four steps of gas exchange is correct?

Accepted Answer

Circulation involves the transport of dissolved $$O_2$$ and $$CO_2$$ throughout the body.

Question 7

Which animal group is an exception to the limitation of open circulatory systems due to their specialized respiratory or vascular adaptations?

Accepted Answer

Pancrustaceans (insects and crustaceans)

Question 8

What is the primary reason diffusion is only efficient over small distances in animal tissues?

Accepted Answer

Diffusion time is proportional to the square of the distance ($$t \propto d^2$).

Question 9

Which of the following best explains why blood pressure drops significantly in capillaries?

Accepted Answer

Capillaries have a large total cross-sectional area, decreasing velocity and pressure.

Question 10

Which structure in the heart initiates the electrical signal that triggers contraction?

Accepted Answer

Sinoatrial (SA) node

Question 11

What is the main function of intercalated discs in cardiac muscle cells?

Accepted Answer

They allow electrical signals to pass directly from cell to cell via gap junctions.

Question 12

Which of the following correctly describes the difference between arteries and veins in a closed circulatory system?

Accepted Answer

Arteries carry blood away from the heart under high pressure; veins carry blood toward the heart under low pressure.

Question 13

Which of the following is a direct response to falling blood pressure detected by baroreceptors?

Accepted Answer

Increase in cardiac output and constriction of arterioles serving noncritical tissues.

Question 14

Which of the following is TRUE about the lymphatic system?

Accepted Answer

It collects excess interstitial fluid and returns it to major veins entering the heart.

Question 15

In mammals, which process creates the negative pressure required for inhalation?

Accepted Answer

Downward movement of the diaphragm

Question 16

Which of the following best explains why aquatic animals must process much more water than air breathers to obtain the same amount of oxygen?

Accepted Answer

Water contains much less oxygen per unit volume than air.

Question 17

Which of the following is a correct statement about hemoglobin?

Accepted Answer

Hemoglobin is an iron-based protein that efficiently loads and unloads oxygen at respiratory surfaces and tissues.

Question 18

Which of the following equations correctly describes the calculation of partial pressure of a gas in a mixture?

Accepted Answer

$$P_{gas} = 	ext{fractional composition} 	imes 	ext{total pressure}$$

Question 19

Which of the following is a unique feature of avian (bird) lung ventilation compared to mammals?

Accepted Answer

Birds exchange gases during both inhalation and exhalation due to unidirectional airflow.

Circulation & Gas Exchange: Structure and Function in Animals

Study Guide - Practice Questions