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Respiratory System Anatomy & Physiology Flashcards

7 cards from real CRE practice questions. Tap to flip, then mark Knew It or Still Learning — missed cards come back until you master them.

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  1. The Hering-Breuer reflex is triggered by stretch receptors in the lung and primarily acts to:

    Answer: Terminate inspiration as the lung reaches adequate inflation

    Pulmonary stretch receptors activated at peak inflation send signals via the vagus nerve to inhibit further inspiration, preventing over-inflation.

  2. Which chemoreceptors are MOST sensitive to acute changes in PaCO₂?

    Answer: Central chemoreceptors in the medulla oblongata

    Central chemoreceptors in the medullary ventral surface respond rapidly to CO₂-driven changes in cerebrospinal fluid pH, making them the primary CO₂ sensors.

  3. Pulmonary vascular resistance (PVR) is LOWEST at which lung volume?

    Answer: Functional residual capacity

    PVR is minimized at FRC because alveolar vessels are optimally distended without being over-stretched and extra-alveolar vessels are not compressed, giving the lowest combined resistance.

  4. Oxygen delivery (DO₂) is calculated as the product of cardiac output and:

    Answer: Arterial oxygen content (CaO₂)

    DO₂ = CO × CaO₂, where CaO₂ accounts for both hemoglobin-bound oxygen (1.34 × Hb × SaO₂) and dissolved oxygen (0.0031 × PaO₂).

  5. The right main stem bronchus is more vertical and wider than the left, making it the more common site for:

    Answer: Foreign body aspiration

    The more vertical angle (approximately 25° from vertical) and larger diameter of the right main stem bronchus causes aspirated objects to preferentially lodge on the right side.

  6. In the oxygen-hemoglobin dissociation curve, a rightward shift indicates:

    Answer: Reduced hemoglobin affinity for oxygen, facilitating tissue unloading

    A rightward shift (Bohr effect) decreases hemoglobin's affinity for O₂, promoting release of O₂ to metabolically active tissues under conditions of acidosis, hypercapnia, fever, or elevated 2,3-DPG.

  7. Which zone of the lung (West's zones) has the highest V/Q ratio under normal upright conditions?

    Answer: Zone 1 (apex)

    Zone 1 (lung apex) receives relatively more ventilation than perfusion due to gravity's effect on blood flow, resulting in the highest V/Q ratio and the least efficient gas exchange per unit of blood.