Question 1

Which of the following occurs with the exhalation of air from human lungs?

Accepted Answer

During exhalation, the volume of the thoracic cavity decreases as the diaphragm relaxes and moves upwards, causing the lungs to recoil and expel air out. The rib cage also moves downwards and inwards during exhalation. The residual volume of the lungs, which is the air that remains in the lungs after maximal exhalation, actually increases during exhalation as some air is trapped in the alveoli. The epiglottis is not directly involved in the process of breathing.

Question 2

Countercurrent exchange in the fish gill helps to maximize which of the following?

Accepted Answer

Countercurrent exchange in the fish gill helps to maximize diffusion by creating a concentration gradient that allows for efficient oxygen uptake and carbon dioxide removal.

Question 3

Use the following information to answer the next questions.
Atmospheric pressure at sea level is equal to a column of 760 mm Hg.
Oxygen makes up 21% of the atmosphere by volume.
-What is the partial pressure of oxygen (PO2)?

Accepted Answer

The partial pressure of oxygen can be found by multiplying the total atmospheric pressure by the fraction of oxygen in the atmosphere. Therefore, PO2 = 760 mm Hg x 0.21 = 160 mm Hg.

Question 4

Which of the following lung volumes would be different in a person at rest compared with when the person exercises?

Accepted Answer

Tidal volume increases during exercise as the body requires more oxygen and needs to expel more carbon dioxide. Vital capacity, residual volume, and total lung capacity remain relatively constant regardless of activity level.

Question 5

A person with a tidal volume of 450 mL, a vital capacity of 4,000 mL, and a residual volume of 1,000 mL would have a potential total lung capacity of

Accepted Answer

Total lung capacity is the sum of vital capacity and residual volume. Therefore, potential total lung capacity would be 4,000 mL + 1,000 mL = 5,000 mL. Option D is the closest to this number.

Question 6

A group of students was designing an experiment to test the effect of smoking on grass frogs. They hypothesized that to keep the frogs in a smoke-filled environment for defined periods would result in lung cancer in the animals. However, when they searched for previously published information to shore up their hypothesis, they discovered they were quite wrong in their original assessment. Even though they were never going to go ahead with their experiment (so as not to harm frogs needlessly)they knew that a more likely outcome would be which of the following?

Accepted Answer

The answer of A group of students was designing an...

Question 7

The blood level of which gas is most important in controlling human respiration rate?

Accepted Answer

Carbon dioxide is the gas that most directly affects the respiratory rate. When carbon dioxide levels rise in the blood, it triggers an increase in breathing to eliminate the excess carbon dioxide and bring oxygen in.

Question 8

Air rushes into the lungs of humans during inhalation because

Accepted Answer

During inhalation, the rib muscles and diaphragm contract, causing an expansion of the thoracic cavity, which increases lung volume. This creates a decrease in pressure within the lungs, causing air to flow from the outside environment into the respiratory tract.

Question 9

The following questions refer to the data shown below.
Blood entering a capillary bed of a vertebrate was measured for the pressures exerted by various factors.
 $$\begin{array} { l c c } 
& \begin{array} { c } 
\text { Arterial End of } \
\text { Capillary Bed }
\end{array} & \begin{array} { c } 
\text { Venous End of } \
\text { Capillary Bed }
\end{array} \
\hline \text { Hydrostatic pressure } & 10 \mathrm {~mm} \mathrm { Hg } & 14 \mathrm {~mm} \mathrm { Hg } \
\text { Osmotic pressure } & 26 \mathrm {~mm} \mathrm { Hg } & 26 \mathrm {~mm} \mathrm { Hg } \
\mathrm { PO } _ { 2 } & 100 \mathrm {~mm} \mathrm { Hg } & 42 \mathrm {~mm} \mathrm { Hg } \
\mathrm { PCO } _ { 2 } & 40 \mathrm {~mm} \mathrm { Hg } & 46 \mathrm {~mm} \mathrm { Hg }
\end{array}$$ 
Figure 42.1
-For this capillary bed, which of the following statements is correct?

Accepted Answer

Fluids leave the capillaries on the arterial side due to higher hydrostatic pressure and re-enter on the venous side where osmotic pressure is relatively higher compared to hydrostatic pressure.

Question 10

At an atmospheric pressure of 870 mm Hg, what is the contribution of oxygen?

Accepted Answer

The answer of At an atmospheric pressure of 870 mm...

Question 11

Where do air-breathing insects carry out gas exchange?

Accepted Answer

Air-breathing insects carry out gas exchange across the membranes of cells, primarily through a network of tracheae and tracheoles that deliver oxygen directly to tissues.

Question 12

Why is the respiratory system of a bird more efficient than the human respiratory system?

Accepted Answer

Birds have a unique respiratory system where air flows in one direction through their lungs, preventing the mixing of inhaled and exhaled air, which allows for more efficient gas exchange.

Question 13

An oil-water mixture is used as a spray against mosquitoes. How might this spray also affect gas exchange in other insects?

Accepted Answer

Insects breathe through a tracheal system, not lungs or capillaries. The oil could block the spiracles, which are the openings to the tracheal system, affecting gas exchange.

Question 14

Some human infants, especially those born prematurely, suffer serious respiratory failure. This most probably relates to which of the following?

Accepted Answer

Surfactant is a substance that helps to reduce surface tension in the lungs, allowing them to expand and contract easily. Premature infants may not produce enough surfactant, leading to respiratory failure.

Question 15

Breathing is usually regulated by

Accepted Answer

Breathing is regulated by various sensors in the body that detect changes in the levels of carbon dioxide, oxygen, and pH in the blood. These sensors signal the respiratory center in the brainstem, which adjusts the rate and depth of respiration to maintain homeostasis.

Question 16

Which of the following is an example of countercurrent exchange?

Accepted Answer

Countercurrent exchange involves the opposite movement of two different fluids in close proximity, allowing for efficient transfer of substances between them. The flow of water across the gills of a fish and that of blood within those gills is a classic example of countercurrent exchange, as the water flows in one direction while the blood flows in the opposite direction, maximizing oxygen exchange. The other choices do not involve true countercurrent exchange.

Question 17

Use the following information to answer the next questions.
Atmospheric pressure at sea level is equal to a column of 760 mm Hg.
Oxygen makes up 21% of the atmosphere by volume.
-If the partial pressure of CO2 at sea level is approximately 0.23 mm Hg, how does this influence gas exchange in terrestrial animals?

Accepted Answer

The higher partial pressure of oxygen compared to carbon dioxide at sea level facilitates the diffusion of oxygen into the blood and the release of carbon dioxide from the blood in the lungs.

Question 18

At the summit of a high mountain, the atmospheric pressure is 380 mm Hg. If the atmosphere is still composed of 21% oxygen, what is the partial pressure of oxygen at this altitude?

Accepted Answer

The partial pressure of oxygen at this altitude can be found by multiplying the atmospheric pressure by the fraction of oxygen in the atmosphere. 
Partial Pressure of Oxygen = 380 mmHg x 0.21 = 79.8 mmHg ≈ 80 mmHg. Therefore, the correct answer is choice B.

Question 19

Tidal volume in respiration is analogous to what measurement in cardiac physiology?

Accepted Answer

Tidal volume is the amount of air inspired or expired during a single breath, while stroke volume is the amount of blood ejected by the heart during a single heartbeat. Both tidal volume and stroke volume represent the amount of a substance (air or blood) moved with each single cycle.

Question 20

At sea level, atmospheric pressure is 760 mm Hg. Oxygen gas is approximately 21% of the total gases in the atmosphere. What is the approximate partial pressure of oxygen?

Accepted Answer

The partial pressure of a gas is calculated by multiplying the total pressure by the percentage of the gas. At sea level, the atmospheric pressure is 760 mm Hg, and oxygen makes up about 21% of the atmosphere. Therefore, the partial pressure of oxygen is approximately 0.21 * 760 mm Hg = 159.6 mm Hg, which is closest to 160.0 mm Hg.

Quiz 42: Circulation and Gas Exchange