Cardiovascular Anatomy and Physiology Flashcards

Which electrolyte is most critical for maintaining the cardiac action potential and myocardial contractility?

Answer: Calcium

Calcium influx during phase 2 (plateau) of the action potential couples electrical excitation to myocardial contraction.

The sympathetic nervous system affects the heart primarily by:

Answer: Increasing heart rate and contractility

Sympathetic stimulation releases norepinephrine, which binds beta-1 receptors to increase heart rate (chronotropy) and contractility (inotropy).

What is the primary function of the Purkinje fibers?

Answer: Rapidly distribute the electrical impulse throughout the ventricles

Purkinje fibers conduct impulses very rapidly through the ventricular walls, ensuring near-simultaneous contraction of both ventricles.

Hypokalemia (low potassium) is most likely to cause which ECG change?

Answer: Prominent U waves

Hypokalemia characteristically produces prominent U waves (often larger than the T wave) and may predispose to dysrhythmias.

Which vessel carries oxygenated blood from the lungs to the heart?

Answer: Pulmonary vein

The four pulmonary veins return oxygenated blood from the lungs to the left atrium, completing the pulmonary circuit.

An increase in vagal (parasympathetic) tone will most directly result in:

Answer: Sinus bradycardia

Vagal stimulation releases acetylcholine, which decreases SA node automaticity and slows AV conduction, lowering heart rate.

The left ventricle has a thicker wall than the right ventricle because it must:

Answer: Pump blood against the higher resistance of the systemic circulation

The left ventricle pumps against systemic vascular resistance (~120 mmHg), which is much higher than pulmonary resistance, requiring greater wall mass.