Download PDF – RRB PM-UT 02 – Anatomy & Physiology Practice Test 2: Cardiovascular & Lymphatic Systems

RRB PM-UT 02 – Anatomy & Physiology Practice Test 2: Cardiovascular & Lymphatic Systems

Q1. Which structural layer of the heart wall contains specialized intercalated discs with gap junctions for electrical syncytium formation?

A) Fibrous pericardium

B) Myocardium

C) Parietal serous pericardium

D) Endocardium

Answer: (B)

The myocardium consists of branching cardiac muscle cells (cardiomyocytes) connected end-to-end by intercalated discs. These discs contain desmosomes for mechanical adherence and gap junctions that allow direct ionic current flow, enabling the myocardium to function physiologically as an electrical syncytium. The endocardium is the endothelial lining, while the pericardium forms the protective fibroserous sac.

Q2. What is the physiological role of the annulus fibrosus cordis (fibrous skeleton of the heart)?

A) Generating spontaneous rhythmic pacemaker potentials

B) Electrically insulating the atria from the ventricles except at the AV bundle

C) Synthesizing atrial natriuretic peptide (ANP) during atrial distension

D) Facilitating non-selective paracellular ion transfer between atria and ventricles

Answer: (B)

The fibrous skeleton of the heart (annulus fibrosus) consists of four dense collagenous rings surrounding the cardiac valves. It provides mechanical support for valve leaflets, anchors myocardial fibers, and acts as an electrical insulator between atrial and ventricular musculature, ensuring that conduction passes exclusively through the Atrioventricular (AV) bundle of His.

Q3. Which heart valve consists of two cusps and prevents backward flow from the left ventricle into the left atrium during ventricular systole?

A) Tricuspid valve

B) Pulmonary semilunar valve

C) Mitral (Bicuspid) valve

D) Aortic semilunar valve

Answer: (C)

The mitral (bicuspid) valve is situated at the left atrioventricular orifice and possesses two cusps (anterior and posterior) anchored by chordae tendineae to papillary muscles. It closes during left ventricular systole to prevent regurgitation into the left atrium. The tricuspid valve has three cusps and is located between the right atrium and right ventricle.

Q4. Where is the primary physiological pacemaker of the human heart anatomically situated?

A) Interventricular septum near the apex

B) Right atrium near the opening of the superior vena cava

C) Interatrial septum adjacent to the coronary sinus

D) Left atrium near the entry of pulmonary veins

Answer: (B)

The Sinoatrial (SA) node, the intrinsic pacemaker of the heart, is an oval strip of specialized subepicardial neuromuscular tissue located in the anterolateral wall of the right atrium, immediately inferior to the ostium of the superior vena cava. It generates spontaneous action potentials at an intrinsic rate of 60 to 100 impulses per minute.

Q5. What electrophysiological phenomenon accounts for the spontaneous pacemaker prepotential (Phase 4 depolarization) in SA nodal tissue?

A) Inward funny current (If) carried by hyperpolarization-activated cyclic nucleotide-gated channels

B) Rapid sodium influx through voltage-gated Nav1.5 fast channels

C) Continuous outward potassium current through delayed rectifier channels

D) Sustained active pumping of sodium out of the cell via Na+/K+-ATPase

Answer: (A)

Phase 4 spontaneous diastolic depolarization in SA nodal cells is mediated by the 'funny' current (If), an inward sodium (and potassium) current through hyperpolarization-activated cyclic nucleotide-gated (HCN4) channels activated at hyperpolarized potentials (-40 to -60 mV). This brings the membrane potential to threshold for transient (T-type) and long-lasting (L-type) Ca2+ channel opening. Fast Nav1.5 channels are absent or inactivated in nodal tissue.

Q6. What is the primary physiological function of the inherent conduction delay of approximately 0.09 to 0.12 seconds at the Atrioventricular (AV) node?

A) Preventing backflow of blood through closed semilunar valves

B) Allowing adequate time for atrial systole to complete ventricular filling before ventricular contraction

C) Preventing premature repolarization of the Purkinje arborization network

D) Accelerating retrograde conduction velocity back to the sinoatrial node

Answer: (B)

The AV node exhibits slow conduction velocity (approx. 0.05 m/s) due to smaller fiber diameters, fewer gap junctions, and calcium-dependent depolarization. This introduces an intrinsic delay of roughly 0.09 to 0.12 seconds (visible on ECG as the PR segment), ensuring that atrial contraction is fully completed to optimize ventricular end-diastolic volume prior to ventricular systole.

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