MSK Quiz#12, Motoneuron Action Potentials and Muscle Contraction

1. A 24-year-old weightlifter presents with muscle weakness and fatigue. Electromyography shows decreased amplitude in motor unit action potentials (MUAPs) with normal conduction velocity. Which of the following changes in the neuromuscular junction best explains this finding? 

Question 1 of 5

2. During a physiology lab, a student observes that the addition of a certain toxin to a muscle preparation results in sustained muscle contraction. This toxin most likely mimics the effect of which of the following? 

Question 2 of 5

3. In a patient with myasthenia gravis, which of the following pathophysiological mechanisms is primarily responsible for the observed muscle weakness and fatigue? 

Question 3 of 5

4. Which of the following best describes the role of calcium ions in muscle contraction? 

Question 4 of 5

5. A drug that blocks voltage-gated sodium channels in the sarcolemma would be expected to have which of the following effects on muscle contraction? 

Question 5 of 5


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