Cardiovascular Physiology and Pharmacology Flashcards

Which of the following best describes the Frank-Starling mechanism?

Answer: Stroke volume increases with increased ventricular end-diastolic volume

The Frank-Starling mechanism states that stroke volume increases as ventricular end-diastolic volume (preload) increases, due to optimal actin-myosin overlap.

The velocity of conduction is SLOWEST through which cardiac structure?

Answer: AV node

The AV node has the slowest conduction velocity (~0.05 m/s), creating the essential delay between atrial and ventricular contraction.

A patient receives a drug that selectively blocks I_f (funny current) channels. What is the primary effect?

Answer: Decreased automaticity of the SA node

I_f channels carry mixed Na+/K+ inward current responsible for pacemaker depolarization; blocking them (e.g., ivabradine) reduces SA node automaticity and heart rate.

Which parameter is MOST directly measured by thermodilution pulmonary artery catheter?

Answer: Cardiac output

Thermodilution measures cardiac output directly by detecting temperature change in the pulmonary artery after cold saline injection into the right atrium.

Levosimendan improves cardiac contractility primarily by:

Answer: Sensitizing troponin C to calcium

Levosimendan binds to troponin C and stabilizes the calcium-troponin C complex, increasing myofilament calcium sensitivity without raising intracellular calcium.

During a hypertensive crisis, sodium nitroprusside acts primarily by:

Answer: Releasing nitric oxide causing smooth muscle relaxation

Sodium nitroprusside spontaneously releases nitric oxide, which activates guanylate cyclase in vascular smooth muscle, increasing cGMP and causing vasodilation.

Which of the following best describes pulsus paradoxus?

Answer: An exaggerated fall in systolic BP >10 mmHg during inspiration

Pulsus paradoxus is an exaggerated inspiratory decrease in systolic BP >10 mmHg, classically seen in cardiac tamponade and severe asthma.