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5.2 Muscle Contraction — Test 1
Q1. Calcium released in skeletal muscle in response to a stimulus binds to:✓ Troponin
Q2. The essential ion required for skeletal muscle contraction is:✓ Calcium
Q3. Rigor mortis (stiffening of muscles after death) is due to:✓ Depletion of ATP
Q4. The role of calcium in muscle contraction is that it:✓ Binds troponin, moving tropomyosin to expose actin sites
Q5. Which protein binds calcium during excitation–contraction coupling in skeletal muscle?✓ Troponin
Q6. What blocks myosin from binding to actin when the muscle is at rest?✓ Tropomyosin
Q7. The neurotransmitter at the neuromuscular junction is:✓ Acetylcholine
Q8. Acetylcholinesterase, which terminates signalling at the neuromuscular junction, is:✓ Inhibited by organophosphates
Q9. The contractile protein of a muscle fibre that has ATPase activity is:✓ Myosin
Q10. Which one is the contractile protein of a muscle fibre?✓ Actin (and myosin)
Q11. During excitation–contraction coupling, the action potential triggers contraction by causing:✓ Calcium release from the sarcoplasmic reticulum
Q12. Rigor mortis eventually disappears because:✓ Tissue enzymes break down the muscle proteins (autolysis)
Q13. The chemical ions chiefly responsible for the muscle action potential (impulse) are:✓ Sodium and potassium
Q14. Myosin light chain kinase (MLCK), important in smooth-muscle contraction, is activated by:✓ The calcium–calmodulin complex
Q15. A defect of acetylcholine receptors at the neuromuscular junction causes the disease:✓ Myasthenia gravis
Q16. Quantal transmission at the neuromuscular junction refers to:✓ Release of neurotransmitter in discrete packets (vesicles)
Q17. Calcium ions are needed for all the following EXCEPT:✓ Breakdown of acetylcholine in the synapse
5.2 Muscle Contraction — Test 2
Q18. The structure that anchors thin filaments and defines the boundary of a sarcomere is the:✓ Z line
Q19. During the cross-bridge cycle, ATP is required to:✓ Detach the myosin head from actin
Q20. At the neuromuscular junction, the arriving impulse causes the release of acetylcholine by triggering:✓ Calcium entry into the nerve terminal
Q21. The neurotransmitter released at the neuromuscular junction to trigger contraction is:✓ Acetylcholine
Q22. During contraction, the myosin heads bind to ____ and pull the thin filaments inward:✓ Actin
Q23. In the cross-bridge cycle, ATP binding to the myosin head causes it to:✓ Detach from actin
Q24. Calcium triggers contraction by binding to ____, which moves tropomyosin away from the actin binding sites:✓ Troponin
Q25. Excitation–contraction coupling refers to the link between:✓ The muscle action potential and calcium release
Q26. Relaxation of a muscle occurs when calcium is:✓ Pumped back into the sarcoplasmic reticulum
Q27. The arrival of an impulse at the nerve terminal releases acetylcholine by triggering:✓ Calcium entry into the terminal
Q28. The enzyme that breaks down acetylcholine at the neuromuscular junction is:✓ Acetylcholinesterase
Q29. Rigor mortis after death is caused by:✓ Depletion of ATP, locking myosin onto actin
Q30. The contractile mechanism of muscle is best described by the:✓ Sliding filament theory
Q31. Myasthenia gravis, causing muscle weakness, results from an attack on the:✓ Acetylcholine receptors at the neuromuscular junction
Q32. A muscle's contraction in response to a single brief stimulus is a:✓ Twitch
Q33. During contraction, which band of the sarcomere does NOT change in length?✓ The A-band