A 22-year-old previously healthy student who has been studying all night stands up quickly and experiences brief dizziness. Vital signs show BP 92/58 mmHg, HR 118/min, RR 16/min, SpO2 98% on room air. He denies chest pain, dyspnea, and orthostatic symptoms persist only seconds. ECG shows normal sinus tachycardia. He takes no medications. Which of the following immediate physiologic response most likely restores blood pressure in this setting?
- A)Increased vagal output due to increased aortic arch stretch
- B)Increased atrial stretch causing reflex bradycardia
- C)Decreased renin release from juxtaglomerular cells within seconds
- D)Increased carotid sinus firing leading to decreased sympathetic tone
- E)Decreased baroreceptor firing leading to increased sympathetic outflowGABARITO
Explicação
Decreased baroreceptor firing leading to increased sympathetic outflow is correct. Standing suddenly lowers venous return and arterial pressure, which reduces stretch at the carotid sinus and aortic arch. The medulla responds by increasing sympathetic tone and... Ver explicação completa e trilha adaptativa →