A patient shows impaired smooth muscle relaxation but no effects of cardiac or skeletal muscle relaxations. The electrolyte levels are normal. Which of the following statements is the best explanation for this defect? Select one: a. The patient has a mutation in their myosin light chain phosphatase which is impairing function. b. The patient has a mutation in their myosin light chain kinase which is impairing function. c. The patient has a mutation in their L-type Ca2+ channel which is impairing function d. The patient has a mutation in their troponin which is impairing function
Added by Tyler L.
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Myosin light chain kinase (MLCK) phosphorylates the myosin light chains, leading to contraction, while myosin light chain phosphatase (MLCP) dephosphorylates the myosin light chains, leading to relaxation. Since the patient has impaired smooth muscle relaxation Show more…
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3) Slow twitch muscle fibers: a) have characteristically high myoglobin levels, b) are fatigue resistant, c) have few mitochondria, d) a & b, e) a & c. 4) Lo represents: a) optimal sarcomere overlap, b) longest sarcomere length, c) shortest sarcomere length, d) suboptimal sarcomere overlap, e) none of the above. 5) The latch property of smooth muscle refers to the ability of smooth muscle to maintain: a) the rate of ATP production after stimulation, b) maintaining force production while decreasing the rate of energy utilization, c) force in the absence of myosin light chain phosphorylation, d) an entirely relaxed state independent of free Ca++ levels, e) a decreased membrane potential. 6) Which of the following will increase stroke volume: a) reduced activity of cardiac sympathetic nerves, b) increased arterial pressure, c) reduced end diastolic volume, d) low extracellular Ca2+, e) increased ventricular filling pressure.
Adi S.
Which of the following best explains the cellular mechanisms involved in the process of summation in skeletal muscle contraction? a. Increased stimulation frequency results in higher turnover of ATP, which enables the buildup of a greater twitch force. b. Additional motor units are stimulated to contract due to an increase in stimulation frequency, which results in a greater force output from the muscle as a whole. c. Myosin is still bound to actin and the sarcomere is still partially contracted when the muscle is stimulated to contract again. This results in additive levels of force output because the next contraction begins from this state rather than from rest. d. The active transport of calcium ions back into the sarcoplasmic reticulum is accelerated with increased stimulation frequency. This results in longer interactions between actin and myosin, which generates greater muscle tension.
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