CCS Cardiac Anatomy & Physiology 3

Question 1

The sinoatrial (SA) node is normally supplied by a branch of which coronary artery in approximately 60% of individuals?

Accepted Answer

Right coronary artery

Answer

In about 60% of individuals, the SA nodal artery arises from the right coronary artery (RCA).

Question 2

Which phase of the cardiac cycle is associated with the highest myocardial oxygen consumption?

Accepted Answer

Isovolumetric contraction

Answer

Isovolumetric contraction generates maximum wall tension and consumes the most myocardial oxygen.

Question 3

The P-R interval on an ECG represents conduction through which structures?

Accepted Answer

Atria, AV node, and bundle of His

Answer

The PR interval reflects atrial depolarization and conduction delay through the AV node and bundle of His.

Question 4

Which papillary muscle is most vulnerable to ischemia following an inferior myocardial infarction?

Accepted Answer

Posterior medial papillary muscle

Answer

The posteromedial papillary muscle has a single blood supply (usually from the RCA), making it more susceptible to ischemic rupture.

Question 5

What is the approximate normal cardiac output at rest in a healthy adult?

Accepted Answer

5–6 L/min

Answer

Normal resting cardiac output is approximately 5–6 L/min, representing heart rate multiplied by stroke volume.

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