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5.1 Skeletal Muscle Structure — Test 1
Q1. During muscular contraction, the structure that decreases in length is the:✓ Sarcomere
Q2. Which statement is correct for muscle contraction (sliding filament theory)?✓ The A band length remains constant while the I band shortens
Q3. The bundles of myosin (thick) filaments are held centred within the sarcomere by:✓ The M line (and titin)
Q4. In response to a nerve impulse, calcium released from the sarcoplasmic reticulum binds to:✓ Troponin
Q5. The calcium ions that initiate skeletal muscle contraction are released from the:✓ Sarcoplasmic reticulum
Q6. White (fast-twitch) muscle fibres differ from red (slow-twitch) fibres in having:✓ Fewer mitochondria and less myoglobin, relying on glycolysis
Q7. The highest level of succinic dehydrogenase (an oxidative enzyme) is found in:✓ Red (slow-twitch) fibres
Q8. The microscopic contractile unit of skeletal muscle, lying between two Z lines, is the:✓ Sarcomere
Q9. The A band of the sarcomere consists of:✓ Thick filaments (with overlapping thin filaments)
Q10. The I band of the sarcomere contains:✓ Only thin (actin) filaments
Q11. The sarcotubular system that conducts the action potential into the muscle fibre interior consists of:✓ T-tubules (transverse tubules)
Q12. The thick filaments of skeletal muscle are composed of:✓ Myosin
Q13. The thin filaments of skeletal muscle are composed mainly of:✓ Actin (with troponin and tropomyosin)
Q14. The membrane surrounding a single muscle fibre is the:✓ Sarcolemma
Q15. Athletes may get muscle cramps mainly due to:✓ Accumulation of lactic acid (and electrolyte/fluid imbalance)
5.1 Skeletal Muscle Structure — Test 2
Q16. A correct statement about the sarcomere is that the:✓ A band contains both thick and overlapping thin filaments
Q17. The functional contractile unit of a muscle fibre, lying between two Z-lines, is the:✓ Sarcomere
Q18. The protein that forms the thick filaments of skeletal muscle is:✓ Myosin
Q19. The giant elastic protein that helps centre the thick filaments and gives muscle its passive elasticity is:✓ Titin
Q20. The light I-band of the sarcomere contains:✓ Only thin filaments
Q21. The stored calcium needed for contraction is held in the muscle's:✓ Sarcoplasmic reticulum
Q22. Red (slow-twitch) muscle fibres are suited to sustained activity because they are rich in:✓ Mitochondria and myoglobin
Q23. The transverse (T) tubules of the muscle fibre function to:✓ Carry the action potential deep into the fibre
Q24. The A-band of the sarcomere corresponds to the length of the:✓ Thick filaments
Q25. The membrane surrounding the whole muscle fibre is the:✓ Sarcolemma
Q26. Skeletal muscle appears striated under the microscope because of the:✓ Regular arrangement of overlapping thick and thin filaments
Q27. Each skeletal muscle fibre is:✓ Multinucleated (formed by fusion of cells)
Q28. A motor unit consists of:✓ A motor neuron and all the muscle fibres it innervates
Q29. The Z-line (Z-disc) of the sarcomere functions to:✓ Anchor the thin filaments and define sarcomere boundaries