Respiratory System Practice Questions

Q: Which of the following statements about peripheral chemoreceptors is true?

Sensitive to hypoxia. ***Sensitive to hypoxia*** - **Peripheral chemoreceptors**, located in the **carotid bodies** and **aortic arch**, are highly sensitive to decreases in arterial **PO2 (hypoxia)**. - This response is crucial for initiating increased ventilation to correct low oxygen levels. *Primarily sensitive to PCO2* - While peripheral chemoreceptors do respond to high **PCO2**, the **central chemoreceptors** in the brainstem are the primary and most powerful regulators of ventilation in response to changes in **arterial PCO2**. - The response of peripheral chemoreceptors to PCO2 is secondary to their hypoxia-sensing role. *Insensitive to oxygen levels* - This statement is incorrect as peripheral chemoreceptors are the main physiological sensors for **arterial PO2** and are acutely responsive to hypoxia. - Their sensitivity to falling PO2 becomes significant when arterial PO2 drops below 60 mmHg. *Sensitive to pH changes, but not primarily responsive to hypoxia* - Peripheral chemoreceptors are indeed sensitive to changes in **pH**, particularly metabolic acidosis, largely due to their sensitivity to the resulting changes in PCO2 and direct pH effects. - However, they are also **primarily responsive to hypoxia**, making the latter part of the statement incorrect.

Q: When 2,3-bisphosphoglycerate (2,3-BPG) levels increase in the blood, how would this affect the oxygen-hemoglobin dissociation curve?

Shift to the right. ***Shift to the right*** - An increase in **2,3-BPG** levels causes a **rightward shift** of the oxygen-hemoglobin dissociation curve, indicating a **decreased affinity of hemoglobin for oxygen**. - This shift facilitates the **release of oxygen to tissues**, which is crucial in conditions like **hypoxia** or **anemia**. *Shift to the left* - A leftward shift would imply an **increased affinity of hemoglobin for oxygen**, hindering oxygen release to tissues. - This typically occurs with **decreased 2,3-BPG**, **alkalosis**, **hypothermia**, or presence of **fetal hemoglobin**. *No change* - **2,3-BPG** is a significant allosteric effector of hemoglobin, and its concentration directly impacts oxygen binding. - Therefore, a change in its levels *will* alter the curve, making "no change" an incorrect option. *Decrease in the oxygen carrying capacity* - A rightward shift of the curve affects hemoglobin's *affinity* for oxygen, not its **total oxygen-carrying capacity**. - Oxygen-carrying capacity is primarily determined by the **hemoglobin concentration** in the blood.

Question 1

Which of the following statements about peripheral chemoreceptors is true?

Accepted Answer

Sensitive to hypoxia

Answer

Insensitive to oxygen levels

Answer

Primarily sensitive to PCO2

Answer

Sensitive to pH changes, but not primarily responsive to hypoxia

Question 2

The oxygen-hemoglobin dissociation curve is sigmoid because

Accepted Answer

Binding of one oxygen molecule increases the affinity of binding other O2 molecules

Answer

Binding of one oxygen molecule decreases the affinity of binding other O2 molecules

Answer

Oxygen affinity of Hemoglobin decreases when the pH of blood falls

Answer

Binding of oxygen to Hemoglobin reduces the affinity of Hb for CO2

Question 3

When 2,3-bisphosphoglycerate (2,3-BPG) levels increase in the blood, how would this affect the oxygen-hemoglobin dissociation curve?

Accepted Answer

Shift to the right

Answer

Shift to the left

Answer

No change

Answer

Decrease in the oxygen carrying capacity

Respiratory System — MCQs

Respiratory System — MCQs

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