AP Biology : Systems Physiology

Study concepts, example questions & explanations for AP Biology

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Example Questions

Example Question #4 : Understanding Other Respiratory Anatomy

Which of the following is the correct path of air through the respiratory system?

Possible Answers:

Bronchi, pharynx, larynx, trachea, lungs

Larynx, trachea, bronchi, pharynx, lungs

Larynx, pharynx, bronchi, trachea, lungs

Pharynx, larynx, trachea, bronchi, lungs

Trachea, bronchi, larynx, pharynx, lungs

Correct answer:

Pharynx, larynx, trachea, bronchi, lungs

Explanation:

Air enters the body through the nose or mouth, and is transferred to the pharynx (the upper portion of the throat located at the back of the mouth). The larynx is commonly called the "voice box," and is the lower portion of the throat connected to the pharynx. From there, air enters the trachea and flows into the chest. The trachea branches into two bronchi, which continue to branch and divide as the air is carried into the lungs.

Example Question #5 : Understanding Other Respiratory Anatomy

What is the purpose of the nasal passage?

Possible Answers:

The nasal passage allows transfer of oxygen to the nose and face

The nasal passage is largely vestigial in humans

The nasal passage warms or cools air to body temperature and filters air

The nasal passage filters air

Correct answer:

The nasal passage warms or cools air to body temperature and filters air

Explanation:

The nasal passage's main function is to heat or cool air before it enters the lungs. The cilia, mucous and hair also help filter air since the respiratory system is very sensitive to allergens and infection. Also, the lungs need to be kept moist and lubricated, so dry air is damaging. No gas exchange occurs in the nasal passage, it is merely a conduction zone through which air must travel before it gets to the alveoli where gas exchange occurs with the pulmonary capillaries.

Example Question #6 : Understanding Other Respiratory Anatomy

Before it enters the lungs, air must pass through which of the following structures?

Possible Answers:

Nephrons

The pharynx

The esophagus

Alveoli

Correct answer:

The pharynx

Explanation:

After entering the nose and mouth, air is passed into the pharynx. It then travels to the larynx, which houses the vocal cords, before entering the trachea. The trachea transports the air into the thoracic cavity before branching into the primary bronchi. The right bronchus carries air to the right lung; the left bronchus carries air to the left lung. Of the given answer options, air only passes through the pharynx before entering the lungs.

Alveoli are found in the lungs and the primary site of gas exchange; however, the question specifies a structure before the air enters the lungs. The esophagus transports food, and is not involved in respiration. Nephrons are the function units of the excretory system, and are located in the kidneys.

Example Question #7 : Understanding Other Respiratory Anatomy

Which portion of the respiratory system extends from the larynx to the bronchi? 

Possible Answers:

Bronchioles

Trachea

Esophagus

Pharynx

Alveoli

Correct answer:

Trachea

Explanation:

Anterior to the esophagus, the trachea begins at the larynx (voice box) and extends down towards the lungs where it splits into the bronchi. The trachea is a conducting structure, meaning no gas exchange occurs in the trachea. Instead, it is held open by "C" shaped rings of cartilage to allow maximum airflow between the lungs and the air in the environment. 

Example Question #8 : Understanding Other Respiratory Anatomy

What is the function of nasal cilia? 

Possible Answers:

To warm, moisturize, and filter inhaled air

Allow for the insertion of a nasal cannula

To create mucus

Olfaction

To support nasal cartilage 

Correct answer:

To warm, moisturize, and filter inhaled air

Explanation:

The nose is the primary passageway of air into the lungs. Before air can safely enter the body, it must be brought to body temperature, moisturized and cleansed of any particles that could damage the respiratory system or cause infection. Mucous is produced by goblet cells. Olfaction is carried out by specialized neurons in the nose that bind to certain molecules and send information to the brain.

Example Question #9 : Understanding Other Respiratory Anatomy

The right lung has __________ lobes, and the left lung has __________ lobes.

Possible Answers:

four . . . two

three . . . three

three . . . two

two . . . three

two . . . two

Correct answer:

three . . . two

Explanation:

The right lung has 3 lobes and left lung has only 2 lobes to allow room for the heart. The majority of the heart is on the left side of the body since the left ventricle is the largest and thickest-walled chamber of the heart.

Example Question #1 : Understanding Pressure Differentials

Which of the given circulatory system elements has the highest partial pressure of oxygen?

Possible Answers:

Pulmonary arteries

Left atrium

Right atrium

Superior vena cava

Inferior vena cava

Correct answer:

Left atrium

Explanation:

The left atrium receives blood from the pulmonary veins, which carry blood that was freshly oxygenated from the lungs to the heart. The partial pressure of oxygen is always highest soon after oxygenation, thus blood returning from the lungs would have a high partial pressure.

The superior and inferior vena cavae return deoxygenated blood from the body to the heart, and would have very low oxygen partial pressures. The right atrium receives this deoxygenated blood from the vena cavae and transfers it to the right ventricle. From the ventricle, the deoxygenated blood is transported to the lungs via the pulmonary arteries. It only becomes oxygenated again after reaching the lungs, and then returns to the heart through the pulmonary veins.

Example Question #2 : Understanding Pressure Differentials

Which statement describes the pressure in the lungs during exhalation?

Possible Answers:

Lung pressure must be higher than atmospheric pressure

Lung pressure must be equal to atmospheric pressure

Lung pressure must be lower than atmospheric pressure

Lung pressure should not change during the process

Correct answer:

Lung pressure must be higher than atmospheric pressure

Explanation:

This question requires a basic understanding of general chemistry and/or general physics. Remember that gas will only move from an area of high pressure to low pressure; thus, if air is moving out of the lungs, the pressure inside of the lungs must be greater than the pressure outside of the lungs. The point at which air does not move in or out of the lungs is a signal that the pressure of the gas inside of the lungs is equal to that of atmospheric pressure.

In a biological sense, remember that the diaphragm contracts to cause inhalation, which results from negative or decreased pressure in the lungs. When the diaphragm relaxes, the pressure in the lungs must increase again. The increase in pressure forces the air out of the lungs and back into the atmospheric environment.

Example Question #3 : Understanding Pressure Differentials

What causes air to enter human lungs?

Possible Answers:

Smooth muscle in the trachea guides the flow of air into the lungs.

The contraction of the diaphragm increases the volume of the lungs, decreasing the pressure relative to the air outside the body.

The decreased concentration of  in the lungs decreases the density of that air, and denser air outside the body "sinks" into the lungs.

Air diffuses into the lungs due to the decreased  content relative to the air outside our body.

Cillia in the trachea guide the flow of air into the lungs.

Correct answer:

The contraction of the diaphragm increases the volume of the lungs, decreasing the pressure relative to the air outside the body.

Explanation:

Increasing the volume of a container (in this case, the lungs) while keeping the contents (air molecules) the same will decrease the pressure. If no barrier is present (as when holding your breath), pressure will tend to equalize between areas of differing pressure. In order to equalize the pressure, air molecules from outside the body rush into the expanded lungs. The concentration of oxygen does not impact inhalation, and cilia are not used to inhale.

Example Question #3 : Understanding Pressure Differentials

To initiate inhalation, the diaphragm contracts, making the pressure inside the lungs __________.

Possible Answers:

lower than the pressure outside the body

None of these

zero

higher than the pressure outside the body

the same as the pressure outside the body

Correct answer:

lower than the pressure outside the body

Explanation:

Inhalation happens by making the pressure in the lungs lower relative to the pressure outside the body. When the diaphragm contracts, it increases the volume of the thoracic cavity. By Boyle's law, there is an inverse relationship between pressure and volume of a gas. Thus the pressure of the thoracic cavity decreases and since air will flow from high to low pressure, this pulls air into the lungs during inhalation.

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