Which are believed to be important in the early stages of exercise?

Correct Answer: D

Rationale: joint and muscle receptors (mechanoreceptors) drive early exercise hyperpnea via proprioceptive feedback to the medulla. Choice A (central) responds to COâ‚‚/pH later. Choice B (carotid) and C (aortic) sense hypoxia/COâ‚‚, secondary in normoxia. Choice D (stretch) modulates pattern. Muscle spindles and tendon organs signal effort within seconds, initiating ventilation rise before chemical changes, making H key in exercise onset.

Correct Answer: C

Rationale: carotid bodies markedly increase firing when arterial PO₂ falls below 60 mmHg, not 70 mmHg, which is a less pronounced threshold. Choice A is true; central chemoreceptors reside in the medulla, sensing CSF pH. ' hypoxia (via peripheral chemoreceptors) enhances CO₂ sensitivity, amplifying ventilation. Choice D is accurate; carotid bodies have exceptionally high blood flow (≈2000 mL/min/100 g) for rapid gas sensing. Choice E (CO₂ dominance) is also true. The carotid bodies' steep response curve begins at ≈60 mmHg, driving significant respiratory stimulation below this level (e.g., SaO₂ < 90%), as seen in hypoxia studies. At 70 mmHg, stimulation is milder, making C's threshold overstated and thus the incorrect statement.

Correct Answer: A

Rationale: physiological dead space (anatomic + alveolar) equals anatomical dead space (≈150 mL) in healthy lungs at rest alveolar dead space is negligible. Choice B is true; base ventilates more (gravity). Choice C is correct (7 mL/kg, ≈500 mL for 70 kg). Choice D is accurate; resistance drops with volume (airway stretch). Choice E (20x increase) is true. Normal Vₓ/Vₜ (0.3) matches anatomic dead space, making A's ‘larger' claim false.

Correct Answer: B

Rationale: Cough suppressants are medications that reduce the cough reflex, which can be helpful for sleep but may hinder airway clearance during the day when the body needs to expel mucus. For an adolescent with flu symptoms, promoting airway clearance is critical to prevent mucus buildup, which could lead to complications like pneumonia. Using cough suppressants at night allows the client to rest while still enabling productive coughing during the day to clear the airways. Morning, evening, or afternoon use could suppress coughing when it's most needed to expel mucus, especially since flu often involves increased respiratory secretions. The nurse's focus is on balancing symptom relief with the body's natural defense mechanisms, and nighttime use aligns with this goal by prioritizing rest without fully inhibiting airway clearance throughout the day. This approach supports recovery by ensuring mucus is cleared effectively while minimizing discomfort during sleep.

Correct Answer: A

Rationale: The body's natural defenses against influenza include viscous mucus secretions in the respiratory tract that trap viral particles, preventing deeper penetration, and local immunologic defenses like antibodies and inflammatory responses that neutralize the virus at entry points. This inflammation, triggered by immune cells, fights infection but causes symptoms like swelling or fever. Vasodilation occurs, but lowering body temperature isn't a defense fever actually helps combat viruses. Antihistamines aren't naturally released; they're medications, and catecholamines boost alertness, not immunity. Coughing clears mucus, but antidiuretic hormone inhibition isn't a flu defense it relates to fluid balance. The nurse explains mucus and local immunity as key barriers, educating the client on how the body resists influenza naturally before adaptive immunity fully activates, emphasizing their role in limiting viral spread and aiding recovery.