CCT Cardiac Anatomy & Physiology 5 — Questions and Answers
Question 1: Which of the following best defines 'afterload' in cardiac physiology?
- The volume of blood in the ventricle before contraction
- The resistance the ventricle must overcome to eject blood (Correct answer)
- The intrinsic contractile strength of the myocardium
- The rate of venous return to the right heart
Correct answer: The resistance the ventricle must overcome to eject blood
Afterload is the resistance or wall stress that the ventricle must overcome during systole to eject blood, primarily determined by systemic vascular resistance for the left ventricle.
Question 2: In a dominant right coronary circulation, the RCA gives rise to which critical branch supplying the inferior wall?
- Left anterior descending artery
- Posterior descending artery (PDA) (Correct answer)
- Left circumflex artery
- Ramus intermedius
Correct answer: Posterior descending artery (PDA)
In right-dominant circulation (about 70% of people), the RCA gives rise to the posterior descending artery, which supplies the inferior wall of the left ventricle and posterior third of the interventricular septum.
Question 3: Which ion is primarily responsible for the plateau phase (phase 2) of the cardiac action potential?
- Sodium (Na+)
- Potassium (K+)
- Calcium (Ca2+) (Correct answer)
- Chloride (Cl-)
Correct answer: Calcium (Ca2+)
During phase 2 (plateau), slow L-type calcium channels open and Ca2+ influx balances K+ efflux, prolonging depolarization and triggering myocardial contraction via excitation-contraction coupling.
Question 4: The 'a' wave seen in the jugular venous pulse (JVP) corresponds to which cardiac event?
- Ventricular contraction
- Atrial contraction (Correct answer)
- Tricuspid valve closure
- Ventricular filling
Correct answer: Atrial contraction
The 'a' wave of the JVP reflects atrial contraction, which increases right atrial pressure and is transmitted back into the jugular veins just before ventricular systole.
Question 5: Which wall of the left ventricle is most commonly affected in an occlusion of the left circumflex artery?
- Anterior wall
- Lateral wall (Correct answer)
- Inferior wall
- Septal wall
Correct answer: Lateral wall
The left circumflex artery supplies the lateral wall of the left ventricle; its occlusion typically produces a lateral myocardial infarction with ST changes in leads I, aVL, V5, and V6.
Question 6: What is the intrinsic firing rate of the AV node if the SA node fails?
- 60–100 bpm
- 40–60 bpm (Correct answer)
- 20–40 bpm
- 100–150 bpm
Correct answer: 40–60 bpm
The AV node has an intrinsic automaticity of 40–60 bpm; if the SA node fails, the AV node takes over as a subsidiary pacemaker at this slower junctional rate.
Question 7: The moderator band (septomarginal trabecula) is located in which cardiac chamber and carries which conduction fiber?
- Left ventricle; left bundle branch
- Right ventricle; right bundle branch (Correct answer)
- Right atrium; internodal pathway
- Left atrium; Bachmann's bundle
Correct answer: Right ventricle; right bundle branch
The moderator band is a muscular band crossing the right ventricle from the interventricular septum to the anterior papillary muscle, carrying the right bundle branch to the ventricular wall.
CCT Cardiac Anatomy & Physiology 5
Which of the following best defines 'afterload' in cardiac physiology?