Cardiovascular System MCAT Practice Question
A 34-year-old man is brought to the emergency department following a motor vehicle collision. He is alert but anxious, with a heart rate of 118/min, blood pressure of 92/58 mmHg, and respiratory rate of 22/min. Physical examination reveals cool, clammy skin and a delayed capillary refill time. Laboratory studies show a hemoglobin of 9.2 g/dL (previously 14.8 g/dL). The patient is estimated to have lost approximately 30% of his blood volume. Which of the following best explains the integrated compensatory mechanisms occurring in response to this hemorrhagic shock?
Answer choices
- AParasympathetic activation causes bradycardia and increased splanchnic blood flow to maintain visceral perfusion
- BSympathetic stimulation increases heart rate and myocardial contractility while causing venoconstriction and vasoconstriction of non-essential vascular beds to maintain cerebral and coronary perfusionCorrect answer
- CBaroreceptor inhibition leads to decreased sympathetic outflow, allowing vasodilation of all peripheral vascular beds to equalize blood pressure distribution
- DCatecholamine release causes selective vasodilation of the renal and splanchnic circulations to promote fluid reabsorption and restore intravascular volume
- EDecreased arterial pressure stimulates vagal afferents that trigger increased parasympathetic efferent activity to enhance cardiac output through increased stroke volume
- FBaroreceptor reflex activation causes generalized vasodilation of coronary and cerebral vessels while maintaining peripheral vasoconstriction to maximize myocardial perfusion pressure
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