Heart rate is controlled by the cardiac conduction system. Which one of the following is the order of the cardiac conduction system?

Correct Answer: C

Rationale: The sinoatrial node (SA node) is the pacemaker located in the right atrial wall just inferior to the entrance of the superior vena cava. The SA node generates impulses which travel across the atria (followed by atrial systole) and then pause (0.1s) at the atrioventricular node (AV node, sited at the superior part of the inter-ventricular septum) and then to the bundle of His located between the ventricles, splitting into right and left branches down the inter-ventricular septum towards the heart apex, and out to the Purkinje fibres which turn superiorly into the ventricular walls (followed by ventricular systole).

Correct Answer: C

Rationale: The AV bundle (AV node) has the slowest conduction to delay the impulse, allowing atrial contraction before ventricular.

Correct Answer: A

Rationale: Right heart failure increases right atrial pressure due to backflow from the failing right ventricle.

Correct Answer: C

Rationale: Without an ECG, 100 bpm is a common normal value for illustrative purposes; actual calculation requires ECG data.

Correct Answer: A

Rationale: Apo B-100 is the primary apoprotein in LDL, facilitating its binding to receptors.