Understanding the functions and locations of muscular tissues is essential for B. Pharm students preparing for pharmacology, physiology, and pathology modules. This concise guide emphasizes key concepts—skeletal, cardiac and smooth muscle structure, excitation–contraction coupling, muscle fiber types, neuromuscular junction pharmacology, calcium handling, and common disease mechanisms—while linking these to drug actions and toxicology. Keywords to focus on include sarcomere, T-tubules, sarcoplasmic reticulum, calcium-induced calcium release, MLCK, acetylcholinesterase inhibitors, neuromuscular blockers, and muscle regeneration. Mastery of these topics supports rational drug design and therapeutic decision-making. Now let’s test your knowledge with 30 MCQs on this topic.
Q1. Which muscle types display clear striations under light microscopy?
- Smooth muscle only
- Skeletal muscle only
- Cardiac muscle only
- Both skeletal and cardiac muscle
Correct Answer: Both skeletal and cardiac muscle
Q2. Intercalated discs containing desmosomes and gap junctions are a defining feature of which tissue?
- Skeletal muscle
- Smooth muscle
- Cardiac muscle
- Tendon
Correct Answer: Cardiac muscle
Q3. In skeletal muscle excitation–contraction coupling, the primary intracellular Ca2+ source for actin–myosin interaction is:
- Extracellular calcium influx through L-type channels only
- Sarcoplasmic reticulum (SR) calcium release
- Mitochondrial calcium release
- Calcium released from the Golgi apparatus
Correct Answer: Sarcoplasmic reticulum (SR) calcium release
Q4. Which protein constitutes the core of the thin filament and interacts with myosin heads during contraction?
- Myosin
- Actin
- Titin
- Desmin
Correct Answer: Actin
Q5. The neurotransmitter released at the motor end plate to initiate skeletal muscle contraction is:
- Glutamate
- Norepinephrine
- Acetylcholine
- GABA
Correct Answer: Acetylcholine
Q6. What is the main role of transverse (T) tubules in muscle fibers?
- Store calcium for contraction
- Transmit action potentials into the fiber interior to trigger SR release
- Provide structural support between myofibrils
- Synthesize ATP
Correct Answer: Transmit action potentials into the fiber interior to trigger SR release
Q7. Which high-energy phosphate compound provides the fastest immediate source of ATP during the first seconds of intense skeletal muscle activity?
- Glycogen
- Oxidative phosphorylation
- Phosphocreatine (creatine phosphate)
- Lactic acid
Correct Answer: Phosphocreatine (creatine phosphate)
Q8. Type I (slow oxidative) muscle fibers are characterized by all EXCEPT:
- High mitochondrial density
- High myoglobin content
- Rapid, easily fatigable contractions
- Predominance in posture muscles
Correct Answer: Rapid, easily fatigable contractions
Q9. Which agent blocks presynaptic acetylcholine release by cleaving SNARE proteins and is used therapeutically in small doses?
- Neostigmine
- Botulinum toxin
- Succinylcholine
- Tetrodotoxin
Correct Answer: Botulinum toxin
Q10. Which drug acts on the ryanodine receptor to reduce pathological calcium release from the SR and is used in malignant hyperthermia?
- Dantrolene
- Verapamil
- Propranolol
- Neostigmine
Correct Answer: Dantrolene
Q11. Smooth muscle contraction is primarily regulated by Ca2+ binding to which protein that activates MLCK?
- Troponin C
- Calmodulin
- Tropomyosin
- Parvalbumin
Correct Answer: Calmodulin
Q12. Gap junctions that allow electrical coupling between adjacent cells are abundant in:
- Skeletal muscle fibers
- Cardiac muscle and single-unit smooth muscle
- Multiunit smooth muscle only
- Fibroblasts within tendon
Correct Answer: Cardiac muscle and single-unit smooth muscle
Q13. Cardiac muscle excitation–contraction coupling relies on which mechanism?
- Direct SR release without extracellular Ca2+ entry
- Calcium-induced calcium release initiated by L-type Ca2+ channels
- Calmodulin-MLCK pathway only
- Action potentials that do not involve calcium
Correct Answer: Calcium-induced calcium release initiated by L-type Ca2+ channels
Q14. Which enzyme rapidly hydrolyzes acetylcholine in the synaptic cleft to terminate neuromuscular transmission?
- Monoamine oxidase
- Acetylcholinesterase
- Choline acetyltransferase
- Butyrylcholinesterase
Correct Answer: Acetylcholinesterase
Q15. A mutation in the dystrophin gene leads to progressive muscle weakness in which disease?
- Amyotrophic lateral sclerosis
- Duchenne muscular dystrophy
- Myasthenia gravis
- Polymyositis
Correct Answer: Duchenne muscular dystrophy
Q16. Multiunit smooth muscle, found in structures like the iris, is characterized by:
- Extensive electrical coupling via gap junctions
- Each cell contracting independently under autonomic control
- High dependence on pacemaker cells for coordinated contraction
- Striated appearance under light microscopy
Correct Answer: Each cell contracting independently under autonomic control
Q17. Which cell population provides regenerative capacity for adult skeletal muscle after injury?
- Fibroblasts
- Satellite cells
- Endothelial precursor cells
- Adipocytes
Correct Answer: Satellite cells
Q18. Fast glycolytic (Type IIb) fibers are best adapted for which function?
- Endurance and sustained posture
- Rapid, powerful contractions with high anaerobic capacity
- Slow contractions with high mitochondrial content
- Continuous rhythmic contraction like the heart
Correct Answer: Rapid, powerful contractions with high anaerobic capacity
Q19. Which neuromuscular blocker depolarizes the motor end plate causing initial fasciculations followed by flaccid paralysis?
- Pancuronium (non-depolarizing blocker)
- Succinylcholine (depolarizing blocker)
- Neostigmine
- Botulinum toxin
Correct Answer: Succinylcholine (depolarizing blocker)
Q20. Organophosphate poisoning produces skeletal muscle weakness primarily by:
- Blocking voltage-gated sodium channels at the nerve
- Inhibiting acetylcholinesterase and causing cholinergic overstimulation
- Blocking postsynaptic nicotinic receptors permanently
- Directly damaging sarcomeric proteins
Correct Answer: Inhibiting acetylcholinesterase and causing cholinergic overstimulation
Q21. Which giant elastic protein spans half a sarcomere and contributes to passive elasticity and structural integrity?
- Titin
- Nebulin
- Desmin
- Alpha-actinin
Correct Answer: Titin
Q22. A major metabolic cause of acute muscle fatigue during high-intensity exercise is:
- Depletion of mitochondrial DNA
- Accumulation of lactic acid and decreased intracellular pH
- Loss of sarcomeric proteins
- Excessive glycogen storage
Correct Answer: Accumulation of lactic acid and decreased intracellular pH
Q23. Which regulatory protein is present in skeletal muscle but absent in smooth muscle, accounting for differences in contraction control?
- Calmodulin
- Troponin
- Myosin light chain kinase (MLCK)
- Myosin heavy chain
Correct Answer: Troponin
Q24. Which histochemical technique is commonly used to differentiate skeletal muscle fiber types based on myosin ATPase activity?
- Hematoxylin and eosin staining
- Myosin ATPase staining at different pH levels
- Oil Red O staining
- Periodic acid–Schiff (PAS) staining
Correct Answer: Myosin ATPase staining at different pH levels
Q25. Thin (actin) filaments are anchored at which sarcomeric structure largely composed of alpha-actinin?
- M-line
- Z-disc (Z-line)
- I-band center
- H-zone
Correct Answer: Z-disc (Z-line)
Q26. Non-depolarizing neuromuscular blockers such as tubocurarine act by blocking which receptor at the neuromuscular junction?
- Muscarinic acetylcholine receptor
- Nicotinic acetylcholine receptor (Nm subtype)
- GABA-A receptor
- Beta-adrenergic receptor
Correct Answer: Nicotinic acetylcholine receptor (Nm subtype)
Q27. Which tissue is primarily responsible for shivering thermogenesis in humans?
- Smooth muscle
- Skeletal muscle
- Cardiac muscle
- Brown adipose tissue only
Correct Answer: Skeletal muscle
Q28. Cardiac muscle is resistant to tetanic contraction because of its:
- Lack of voltage-gated calcium channels
- Short absolute refractory period relative to skeletal muscle
- Prolonged action potential with long absolute refractory period due to plateau phase
- Absence of sarcoplasmic reticulum
Correct Answer: Prolonged action potential with long absolute refractory period due to plateau phase
Q29. Elevated CK-MB isoenzyme in serum is most indicative of damage to which tissue?
- Smooth muscle
- Cardiac muscle
- Skeletal muscle exclusively
- Renal tubular epithelium
Correct Answer: Cardiac muscle
Q30. Restoration of the resting membrane potential after muscle action potentials primarily requires which membrane transporter?
- Na+/K+ ATPase
- Voltage-gated calcium channel
- Glucose transporter (GLUT4)
- Cl-/HCO3- exchanger
Correct Answer: Na+/K+ ATPase
I am a Registered Pharmacist under the Pharmacy Act, 1948, and the founder of PharmacyFreak.com. I hold a Bachelor of Pharmacy degree from Rungta College of Pharmaceutical Science and Research. With a strong academic foundation and practical knowledge, I am committed to providing accurate, easy-to-understand content to support pharmacy students and professionals. My aim is to make complex pharmaceutical concepts accessible and useful for real-world application.
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