📝 Step 6 — KMU Past Papers & Exam Learning
This section contains KMU-style past paper questions designed to strengthen conceptual understanding. Focus on understanding explanations rather than memorizing answers.
🎯 How to Study KMU Past Papers
- Read the question carefully.
- Think about the answer before looking.
- Read the explanation slowly.
- Understand the reasoning behind the correct answer.
- Revise difficult questions again.
MCQ 1
Question:
A patient develops ventricular arrhythmia after myocardial ischemia. The most likely immediate cellular disturbance responsible for abnormal automaticity is:
Options:
Reduced potassium permeability during resting phase
Failure of calcium binding to troponin
Reduced actin filament synthesis
Increased collagen deposition in myocardium
Failure of myosin ATPase activation
Correct Answer:
Reduced potassium permeability during resting phase
Explanation:
Ischemia alters membrane ion permeability, especially potassium movement, leading to unstable resting membrane potential and arrhythmias.
MCQ 2
Question:
The prolonged plateau phase of ventricular muscle action potential mainly ensures:
Options:
Rapid ventricular filling
Sustained ventricular contraction
Early atrial depolarization
Increased pacemaker discharge
Shortened refractory duration
Correct Answer:
Sustained ventricular contraction
Explanation:
The plateau prolongs depolarization and contraction, allowing adequate ventricular ejection before relaxation.
MCQ 3
Question:
A drug slows AV nodal conduction without significantly affecting skeletal muscle contraction. The drug most likely acts by blocking:
Options:
Fast sodium channels
Transient chloride channels
L-type calcium channels
ATP-sensitive potassium channels
Funny current channels
Correct Answer:
L-type calcium channels
Explanation:
AV nodal depolarization depends mainly on slow calcium channels, unlike skeletal muscle.
MCQ 4
Question:
Cardiac muscle cannot undergo tetanic contraction mainly because cardiac fibers possess:
Options:
Highly developed T-tubules
Short latent period
Prolonged refractory period
Rapid sodium influx
Increased glycogen stores
Correct Answer:
Prolonged refractory period
Explanation:
The refractory period overlaps almost entirely with contraction, preventing summation and tetany.
MCQ 5
Question:
Which feature best explains why extracellular calcium is essential for cardiac muscle contraction but less critical in skeletal muscle?
Options:
Cardiac muscle lacks troponin
Cardiac muscle lacks actin filaments
Calcium entry triggers SR calcium release
Cardiac muscle lacks sarcomeres
Potassium initiates contraction directly
Correct Answer:
Calcium entry triggers SR calcium release
Explanation:
Cardiac muscle depends on calcium-induced calcium release, requiring extracellular calcium entry.
MCQ 6
Question:
A patient receiving a beta-blocker demonstrates reduced heart rate and reduced force of contraction. These effects are best described as:
Options:
Positive chronotropic and positive inotropic
Negative chronotropic and negative inotropic
Positive dromotropic and positive chronotropic
Negative dromotropic and positive inotropic
Positive chronotropic and negative inotropic
Correct Answer:
Negative chronotropic and negative inotropic
Explanation:
Beta-blockers reduce sympathetic stimulation, decreasing heart rate and myocardial contractility.
MCQ 7
Question:
During phase 0 of ventricular action potential, membrane permeability increases primarily for:
Options:
Calcium ions
Chloride ions
Potassium ions
Sodium ions
Magnesium ions
Correct Answer:
Sodium ions
Explanation:
Rapid opening of fast sodium channels causes sudden depolarization during phase 0.
MCQ 8
Question:
Which electrophysiological property is most directly altered in complete heart block?
Options:
Automaticity of ventricular muscle
Contractility of atrial myocardium
Conduction through AV node
Repolarization of Purkinje fibers
Calcium release from sarcoplasmic reticulum
Correct Answer:
Conduction through AV node
Explanation:
Heart block results from impaired conduction between atria and ventricles, commonly at AV node level.
MCQ 9
Question:
The primary physiological consequence of delayed ventricular repolarization is:
Options:
Reduced coronary perfusion
Increased myocardial fibrosis
Electrical instability of myocardium
Failure of atrial contraction
Reduced venous return
Correct Answer:
Electrical instability of myocardium
Explanation:
Delayed repolarization predisposes to dangerous ventricular arrhythmias such as torsades de pointes.
MCQ 10
Question:
A histological feature facilitating coordinated spread of excitation through myocardium is:
Options:
Elastic lamellae
Intercalated discs
Dense collagen bundles
Basement membranes
Satellite cells
Correct Answer:
Intercalated discs
Explanation:
Intercalated discs contain gap junctions that permit rapid electrical communication between cardiac cells.
MCQ 11
Question:
Compared with ventricular muscle fibers, SA nodal cells depolarize mainly due to:
Options:
Rapid sodium influx
Calcium-mediated depolarization
Potassium-mediated depolarization
Chloride-mediated depolarization
Magnesium-mediated depolarization
Correct Answer:
Calcium-mediated depolarization
Explanation:
SA nodal cells rely primarily on calcium influx because fast sodium channels are limited.
MCQ 12
Question:
Which event occurs immediately after calcium binds troponin C in cardiac muscle?
Options:
Closure of sodium channels
Detachment of actin filaments
Exposure of myosin binding sites
Inactivation of SERCA pumps
Opening of potassium channels
Correct Answer:
Exposure of myosin binding sites
Explanation:
Calcium-troponin interaction shifts tropomyosin, exposing actin sites for cross-bridge formation.
MCQ 13
Question:
A patient with severe hyperkalemia is at risk of cardiac arrest because elevated extracellular potassium causes:
Options:
Excessive calcium release from SR
Reduced membrane excitability
Increased ATP synthesis
Enhanced sodium permeability
Prolonged sarcomere shortening
Correct Answer:
Reduced membrane excitability
Explanation:
Hyperkalemia partially depolarizes the membrane, impairing generation and conduction of impulses.
MCQ 14
Question:
The force of cardiac muscle contraction increases after sympathetic stimulation mainly due to:
Options:
Reduced potassium efflux
Enhanced intracellular calcium availability
Shortening of refractory period
Reduced sodium influx
Increased collagen elasticity
Correct Answer:
Enhanced intracellular calcium availability
Explanation:
Sympathetic stimulation increases calcium entry and SR calcium release, strengthening contraction.
MCQ 15
Question:
Which phase of ventricular action potential corresponds to maximum calcium influx into myocardial cells?
Options:
Phase 0
Phase 1
Phase 2
Phase 3
Phase 4
Correct Answer:
Phase 2
Explanation:
The plateau phase is characterized by prolonged calcium entry through L-type calcium channels.
MCQ 16
Question:
A patient with recurrent ventricular tachycardia receives a drug that prolongs refractory period. The therapeutic effect mainly reduces:
Options:
Coronary artery diameter
Re-entry excitation circuits
Myocardial oxygen extraction
Venous return to heart
Atrial filling pressure
Correct Answer:
Re-entry excitation circuits
Explanation:
Prolongation of refractory period interrupts abnormal re-entry pathways causing arrhythmias.
MCQ 17
Question:
Which comparison between cardiac and skeletal muscle is physiologically correct?
Options:
Both require extracellular calcium equally
Both develop tetanic contraction readily
Cardiac muscle has longer action potential duration
Skeletal muscle contains fewer T-tubules
Cardiac muscle lacks troponin complex
Correct Answer:
Cardiac muscle has longer action potential duration
Explanation:
Cardiac action potentials are prolonged because of plateau formation and calcium influx.
MCQ 18
Question:
Reduced activity of SERCA pumps in cardiac muscle would most directly impair:
Options:
Rapid sodium influx
Myocardial relaxation
Gap junction conduction
Pacemaker discharge
AV nodal conduction
Correct Answer:
Myocardial relaxation
Explanation:
SERCA pumps remove cytosolic calcium into SR, enabling cardiac muscle relaxation.
MCQ 19
Question:
A patient develops weak cardiac contractions despite normal nerve supply. The most likely intracellular abnormality is impaired:
Options:
Troponin-calcium interaction
Elastin fiber synthesis
Collagen degradation
Sodium-potassium exchange in erythrocytes
Histamine release from mast cells
Correct Answer:
Troponin-calcium interaction
Explanation:
Cardiac contraction depends on calcium binding to troponin for actin–myosin interaction.
MCQ 20
Question:
The major functional advantage of prolonged ventricular action potential is:
Options:
Facilitation of rapid repetitive stimulation
Synchronization of atrial fibrillation
Maintenance of rhythmic pumping activity
Acceleration of skeletal muscle contraction
Enhancement of venous compliance
Correct Answer:
Maintenance of rhythmic pumping activity
Explanation:
The prolonged action potential ensures coordinated contraction and relaxation necessary for effective cardiac pumping.
📌 Important Exam Strategy
KMU examinations often test integrated understanding rather than isolated facts. Focus on linking anatomy, embryology, histology, and clinical concepts when reviewing questions.
✅ Revision Tip
If you can explain the reason behind the correct answer without looking at notes, your concept is strong.