PNB 2265 EXAM 3 QUESTION BANK: CARDIOVASCULAR & RESPIRATORY PHYSIOLOGY COMPLETE WITH 100% VERIFIED ANSWERS

PNB 2265 EXAM 3 QUESTION BANK: CARDIOVASCULAR & RESPIRATORY PHYSIOLOGY COMPLETE WITH 100% VERIFIED ANSWERS 1. During the cardiac cycle, the second heart sound (S2) corresponds most directly to which event? A) Closure of AV valves B) Opening of semilunar valves C) Closure of semilunar valves D) Isovolumetric contraction Correct Answer: C Explanation: S2, “dub,” occurs at the beginning of ventricular diastole when the aortic and pulmonary semilunar valves close. AV valve closure produces S1. Isovolumetric contraction occurs between S1 and S2. ________________________________________ 2. Which of the following changes would most increase stroke volume via the Frank-Starling mechanism? A) Increased afterload B) Decreased end-diastolic volume C) Increased end-diastolic volume D) Decreased sympathetic tone Correct Answer: C Explanation: Frank-Starling states that increased preload (end-diastolic volume) stretches myocardial fibers, increasing contraction strength and stroke volume. Increased afterload decreases SV. Decreased sympathetic tone would reduce contractility. ________________________________________ 3. A patient has a blood pressure of 90/60 mm Hg and a heart rate of 110 bpm. Which of the following is most likely occurring in their baroreceptor reflex? A) Increased parasympathetic firing to SA node B) Decreased sympathetic outflow to arterioles C) Increased sympathetic outflow to the heart D) Decreased renin release from kidneys Correct Answer: C Explanation: Low BP reduces baroreceptor firing, which disinhibits the medulla’s vasomotor center, increasing sympathetic output (tachycardia, vasoconstriction). Parasympathetic activity decreases, not increases. Renin release increases in hypotension. ________________________________________ 4. Which vessel type has the greatest total cross-sectional area in the circulatory system? A) Aorta B) Arterioles C) Capillaries D) Venules Correct Answer: C Explanation: Capillaries have the greatest total cross-sectional area despite their small individual size. This slows blood flow to facilitate exchange. The aorta has the smallest total cross-sectional area. ________________________________________ 5. In an ECG, the QRS complex represents which electrical event? A) Atrial depolarization B) Ventricular depolarization C) Ventricular repolarization D) AV nodal delay Correct Answer: B Explanation: The QRS complex reflects rapid ventricular depolarization. Atrial depolarization is the P wave. Ventricular repolarization is the T wave. AV nodal delay is the PR segment. ________________________________________ 6. A drug that blocks beta-1 adrenergic receptors would most directly decrease which of the following? A) Peripheral vasoconstriction B) Heart rate and contractility C) Bronchodilation D) Renin release inhibition Correct Answer: B *Explanation: Beta-1 receptors in the heart increase HR and contractility when activated. Blockade reduces these. Beta-2 receptors cause bronchodilation/vasodilation; alpha-1 causes vasoconstriction.* ________________________________________ 7. Which of the following is true regarding lymphatic flow? A) Lymph moves primarily due to the pumping action of the heart B) Lymphatic vessels have no valves C) Lymph flow increases during skeletal muscle contraction D) Edema occurs when lymph flow exceeds capillary filtration Correct Answer: C Explanation: Lymph flow depends on skeletal muscle pumps and valves. The heart does not directly pump lymph. Edema occurs when filtration exceeds lymph drainage, not the reverse. ________________________________________ 8. A decrease in plasma protein concentration (e.g., in liver failure) would most directly affect which pressure? A) Interstitial hydrostatic pressure B) Blood colloid osmotic pressure C) Capillary hydrostatic pressure D) Interstitial colloid osmotic pressure Correct Answer: B Explanation: Plasma proteins (albumin) generate blood colloid osmotic (oncotic) pressure, which draws fluid into capillaries. Low plasma proteins reduce this pressure, favoring edema. ________________________________________ 9. During isovolumetric contraction of the left ventricle, which of the following is true? A) AV and semilunar valves are both open B) AV valve is closed, semilunar valve is open C) AV valve is closed, semilunar valve is closed D) AV valve is open, semilunar valve is closed Correct Answer: C Explanation: Isovolumetric contraction occurs after AV valve closure but before semilunar valve opening. All valves are closed, so volume is constant while pressure rises rapidly.