Respiratory System Practice Questions

Q: Which equation is used to calculate physiological dead space?

Bohr equation. ***Bohr equation*** - The Bohr equation is used to calculate **physiological dead space**, which is the sum of anatomical dead space and alveolar dead space. - It relates the partial pressure of carbon dioxide in arterial blood to the partial pressure of carbon dioxide in expired air, along with **tidal volume** and expired volume. *Dalton's law* - Dalton's law states that the **total pressure** exerted by a mixture of non-reactive gases is equal to the **sum of the partial pressures** of individual gases. - It is used to calculate partial pressures of gases in a mixture, not dead space. *Charles's law* - Charles's law describes the relationship between the **volume and temperature** of a gas at constant pressure. - It states that the volume of a given mass of gas is directly proportional to its absolute temperature. *Boyle's law* - Boyle's law describes the inverse relationship between the **pressure and volume** of a gas at constant temperature. - It is fundamental to understanding mechanics of breathing, but not dead space calculation.

Q: Maximum voluntary ventilation is:

150 L/min. ***150 L/min*** - The **Maximum Voluntary Ventilation (MVV)** represents the largest volume of air that can be breathed in and out using maximal effort over a 10-15 second period. - While it varies among individuals, a typical average value for a healthy adult is approximately **150-170 L/min**. *25 L/min* - This value is significantly lower than the typical MVV; 25 L/min is closer to a normal **resting minute ventilation** (tidal volume multiplied by respiratory rate). - Resting minute ventilation reflects the volume of air exchanged at rest, not the maximum capacity. *50 L/min* - This value is still considerably lower than the average MVV and does not represent the maximum capacity of the respiratory system. - It might be seen in individuals with **severe pulmonary impairment** or at a very high resting metabolic rate. *100 L/min* - While higher than resting values, 100 L/min is generally below the average maximum voluntary ventilation for a healthy adult. - It could represent a MVV in individuals with **mild to moderate respiratory compromise** or less effort during the test.

Q: Which of the following is used for the diagnosis of asthma?

FEV1. ***FEV1*** - **Forced expiratory volume in 1 second (FEV1)** is the gold standard spirometric parameter for asthma diagnosis - Key diagnostic criteria include: - Reduced **FEV1/FVC ratio** (<0.70 or <0.75-0.80 in adults) - **Bronchodilator reversibility**: ≥12% and ≥200 mL increase in FEV1 after inhaled short-acting β2-agonist - This reversibility distinguishes asthma from fixed obstructive diseases like COPD - Serial **peak expiratory flow (PEF)** monitoring can also demonstrate variability characteristic of asthma *Measurement of tidal volume* - **Tidal volume** measures the amount of air inhaled or exhaled during normal breathing (typically ~500 mL at rest) - Not a diagnostic parameter for asthma as it doesn't assess **airway obstruction** or **hyperresponsiveness** - May be reduced during acute exacerbations but lacks specificity for asthma diagnosis *End expiratory flow rate* - Not a standard diagnostic parameter for asthma - While **mid-expiratory flow rates** (FEF25-75%) and **peak expiratory flow (PEF)** are assessed, **FEV1** remains the primary diagnostic measure - FEV1 provides better reproducibility and standardization for diagnosis *Total lung capacity* - **Total lung capacity (TLC)** represents total lung volume after maximal inhalation - May be normal or increased in asthma due to **air trapping** and hyperinflation - Not used as a primary diagnostic criterion as asthma diagnosis focuses on demonstrating **reversible airflow limitation**, not lung volumes

Q: Where are glomus cells primarily located?

Carotid and aortic bodies. ***Carotid and aortic bodies*** - **Glomus cells**, also known as **chemoreceptors**, are primarily located in the **carotid bodies** at the bifurcation of the common carotid artery and in the **aortic bodies** near the aortic arch. - These cells are crucial for monitoring blood oxygen, carbon dioxide, and pH levels, playing a vital role in the body's **respiratory and cardiovascular regulation**. *Bladder* - The bladder’s primary function is to store urine, and it contains specialized cells for distension and contraction, but not **glomus cells** involved in chemoreception. - While the bladder does have nerve endings, they are mainly concerned with detecting stretch and facilitating micturition, not monitoring blood gas levels. *Brain* - The brain contains various specialized cells, including neurons and glial cells, which are responsible for its complex functions. - Although the brain has centers that respond to blood gas changes (e.g., in the medulla), the primary **peripheral chemoreceptors (glomus cells)** are not located within the brain tissue itself. *Kidney* - The kidneys are involved in filtering blood, regulating blood pressure, and producing hormones, containing specialized cells like **juxtaglomerular cells** and podocytes. - However, they do not contain **glomus cells** as a primary site for sensing blood gas levels.

Q: Which of the following contains the PRIMARY central chemoreceptors responsible for detecting CO2 and pH changes in cerebrospinal fluid?

Medulla. ***Medulla*** - The **medulla oblongata** in the brainstem houses the primary central chemoreceptors. - These chemoreceptors are located on the **ventral surface of the medulla** and are highly sensitive to changes in the **pH of the cerebrospinal fluid (CSF)**, which is indirectly affected by the partial pressure of carbon dioxide (PCO2) in arterial blood. - CO2 diffuses across the blood-brain barrier, combines with water to form H+ ions, which directly stimulate these central chemoreceptors. *Baroreceptors in carotid sinus* - **Baroreceptors** primarily detect changes in **arterial blood pressure**, not CO2 or pH levels. - They are located in the carotid sinus and aortic arch and are involved in cardiovascular reflexes, not direct chemoreception for respiratory drive. *Peripheral chemoreceptors in carotid bodies* - **Peripheral chemoreceptors** in the carotid bodies (and aortic bodies) detect changes in **arterial blood O2, CO2, and pH**. - However, they are **peripheral**, not central chemoreceptors, and are the primary detectors of **hypoxemia**. - They contribute to respiratory drive but are secondary to central chemoreceptors for CO2 detection. *All of the above* - This option is incorrect because only the **medulla** contains the primary central chemoreceptors for CO2 and pH detection in CSF. - Baroreceptors detect blood pressure, and peripheral chemoreceptors are not central chemoreceptors.

Q: Which of the following defines vital capacity?

Maximum air that can be expirated after maximum inspiration. ***Maximum air that can be expirated after maximum inspiration*** - **Vital capacity (VC)** is the maximum volume of air that can be exhaled after a maximal inspiration. - It represents the sum of **tidal volume (TV)**, **inspiratory reserve volume (IRV)**, and **expiratory reserve volume (ERV)**. - VC = TV + IRV + ERV *Air in lung after normal expiration* - This describes the **functional residual capacity (FRC)**, which is the volume of air remaining in the lungs after a normal passive exhalation. - FRC = ERV + RV (expiratory reserve volume + residual volume). *Maximum air that can be expirated after normal expiration* - This refers to the **expiratory reserve volume (ERV)**, the additional amount of air that can be exhaled forcibly after a normal passive exhalation. - It is the extra air expelled beyond tidal volume during forced expiration. *Maximum air in lung after end of maximal inspiration* - This definition corresponds to **total lung capacity (TLC)**, which is the maximum volume of air the lungs can hold after a maximal inspiration. - TLC = VC + RV (vital capacity + residual volume).

Q: What does the Hering-Breuer reflex decrease during respiration?

Duration of inspiration. ***Duration of inspiration*** - The **Hering-Breuer reflex** is a protective reflex that prevents overinflation of the lungs by inhibiting further inspiration once the lungs are adequately stretched. - Activation of **stretch receptors** in the bronchial walls sends signals via the vagus nerve to the brainstem, which then inhibits the inspiratory neurons, thus **shortening the inspiratory phase**. *Duration of expiration* - The Hering-Breuer reflex primarily affects inspiration and does not directly shorten the duration of expiration. - Expiration is typically a passive process at rest, driven by the elastic recoil of the lungs, and its duration is not the main target of this reflex. *Depth of inspiration* - While the reflex ultimately limits the **volume of inspired air**, its primary action is to *terminate* inspiration, thus affecting its duration rather than directly reducing the force or 'depth' of each breath. - The **depth of inspiration** is more related to the strength of inspiratory muscle contraction and central respiratory drive. *Depth of expiration* - The Hering-Breuer reflex does not influence the depth of expiration. - Expiration is largely passive, and the depth of expiration is typically not regulated by this reflex unless breathing becomes forced.

Q: Peripheral and central chemoreceptors may both contribute to the increased ventilation that occurs as a result of which of the following?

An increase in arterial carbon dioxide tension. ***An increase in arterial carbon dioxide tension*** - An increase in **arterial PCO2** (hypercapnia) leads to a rapid decrease in the **pH of the cerebrospinal fluid (CSF)**, which strongly stimulates **central chemoreceptors** in the medulla. - While overwhelmingly driven by central chemoreceptors, a significant increase in **arterial PCO2** also causes a slight decrease in **arterial pH**, which can additionally stimulate **peripheral chemoreceptors** in the carotid and aortic bodies, leading to increased ventilation. *A decrease in arterial oxygen content* - A decrease in **arterial oxygen content** (e.g., due to anemia or carbon monoxide poisoning) without a significant drop in **arterial PO2** primarily affects oxygen delivery to tissues. - It does not directly stimulate peripheral chemoreceptors, which are sensitive to **PO2**, not content, nor does it affect central chemoreceptors directly to increase ventilation in this manner. *A decrease in arterial blood pressure* - A decrease in **arterial blood pressure** is sensed by **baroreceptors** and primarily triggers cardiovascular reflexes (e.g., increased heart rate and vasoconstriction) to restore blood pressure. - It does not directly stimulate peripheral or central chemoreceptors to significantly increase ventilation unless severe hypoperfusion leads to significant changes in arterial blood gases. *A decrease in arterial oxygen tension* - A decrease in **arterial oxygen tension (PO2)**, especially when it falls below approximately 60 mmHg, acts as a potent stimulus for **peripheral chemoreceptors**. - However, **central chemoreceptors** are primarily sensitive to **PCO2** and CSF pH, and a decrease in **arterial PO2** alone has little direct effect on their activity.

Question 1

Which equation is used to calculate physiological dead space?

Accepted Answer

Bohr equation

Answer

Dalton's law

Answer

Charles's law

Answer

Boyle's law

Question 2

Maximum voluntary ventilation is:

Accepted Answer

150 L/min

Answer

25 L/min

Answer

50 L/min

Answer

100 L/min

Question 3

Which of the following is used for the diagnosis of asthma?

Accepted Answer

FEV1

Answer

Measurement of tidal volume

Answer

End expiratory flow rate

Answer

Total lung capacity

Question 4

Where are glomus cells primarily located?

Accepted Answer

Carotid and aortic bodies

Answer

Bladder

Answer

Brain

Answer

Kidney

Question 5

Which of the following contains the PRIMARY central chemoreceptors responsible for detecting CO2 and pH changes in cerebrospinal fluid?

Accepted Answer

Medulla

Answer

Baroreceptors in carotid sinus

Answer

Peripheral chemoreceptors in carotid bodies

Answer

All of the above

Question 6

Which of the following defines vital capacity?

Accepted Answer

Maximum air that can be expirated after maximum inspiration

Answer

Air in lung after normal expiration

Answer

Maximum air in lung after end of maximal inspiration

Answer

Maximum air that can be expirated after normal expiration

Question 7

Which of the following statements about lung compliance is NOT true?

Accepted Answer

Measured by intrapleural pressure at different lung volumes.

Answer

Decreased at the height of inspiration.

Answer

Increased in emphysema.

Answer

Increased by surfactant.

Question 8

What does the Hering-Breuer reflex decrease during respiration?

Accepted Answer

Duration of inspiration

Answer

Depth of inspiration

Answer

Depth of expiration

Answer

Duration of expiration

Question 9

What is the Bohr effect in relation to hemoglobin's affinity for oxygen?

Accepted Answer

Decrease in O2 affinity of hemoglobin when the pH of blood falls

Answer

Decrease in CO2 affinity of hemoglobin when the pH of blood falls

Answer

Decrease in O2 affinity of hemoglobin when the pH of blood rises

Answer

Decrease in CO2 affinity of hemoglobin when the pH of blood rises

Question 10

Peripheral and central chemoreceptors may both contribute to the increased ventilation that occurs as a result of which of the following?

Accepted Answer

An increase in arterial carbon dioxide tension

Answer

A decrease in arterial oxygen content

Answer

A decrease in arterial blood pressure

Answer

A decrease in arterial oxygen tension

Respiratory System — MCQs

Respiratory System — MCQs

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