Physiology Flashcards
7 cards from real NBME practice questions. Tap to flip, then mark Knew It or Still Learning — missed cards come back until you master them.
Read the first 7 Physiology flashcards as text
A patient has a cardiac output of 6 L/min and a heart rate of 75 bpm. What is the stroke volume?
Answer: 80 mL
Stroke volume = cardiac output ÷ heart rate = 6000 mL/min ÷ 75 bpm = 80 mL.
During isovolumetric contraction, which valves are open?
Answer: Neither aortic nor mitral valves
During isovolumetric contraction, all four cardiac valves are closed as ventricular pressure rises before the aortic valve opens.
Which condition causes a leftward shift of the oxygen-hemoglobin dissociation curve?
Answer: Alkalosis
Alkalosis raises pH, decreasing H+ concentration and increasing hemoglobin's oxygen affinity, shifting the curve leftward.
Hypoxic pulmonary vasoconstriction primarily serves to:
Answer: Redirect blood to better-ventilated lung segments
Hypoxic pulmonary vasoconstriction diverts blood from poorly oxygenated alveoli to better-ventilated regions, optimizing V/Q matching.
In the West lung zones, which pressure relationship defines Zone 1?
Answer: Alveolar > arterial > venous
Zone 1 (lung apex) has alveolar pressure exceeding arterial pressure, collapsing capillaries and creating dead space with no gas exchange.
A patient develops acute hypoventilation. Which blood gas change occurs FIRST?
Answer: Increased PaCO2
Hypoventilation leads to CO2 retention (increased PaCO2) as a primary event because CO2 production is continuous and its elimination depends entirely on ventilation.
Which vessel type is the primary determinant of systemic vascular resistance?
Answer: Arterioles
Arterioles are the primary resistance vessels; resistance varies inversely with the fourth power of radius (Poiseuille's law), so small arteriolar changes dramatically alter SVR.