A patient came to his physician complaining of muscle weakness.

a. List the locations along the complete motor pathway where some defect could result in muscle weakness. (5)

Upon testing the patient, the following observations were made:

(1) Repetitive voluntary activity was associated with normal action potential activity in the motor nerve, although the patient’s muscles rapidly fatigue and muscle force declined.

(2) Repetitive, direct electrical stimulation of muscle resulted in normally sustained force without evidence of fatigue.

b. Assuming that a single site of pathology is present, where along the motor pathway is this patient’s problem? Explain your reasoning.