List the 3 major classes of motor proteins:

State the function of myofibrils.

A 48-year-old man has hepatic cancer that is unresponsive to standard therapy. He enrolls in a clinical study of a novel chemotherapeutic agent that, as a side effect, blocks kinesin, a component of the cellular microtubular transport system. One week later, he develops skeletal muscle weakness An alteration in which of the following components of the neuromuscular junction is the most likely cause of the muscle weakness? (A) A decrease in the number of postsynaptic neurotransmitter receptors (B) A decrease in the number of presynaptic neurotransmitter vesicles (C) A decrease in the presynaptic neuron calcium permeability (D) Impaired a-motoneuron action potential conduction (E) Impaired skeletal muscle action potential conduction

In your own words briefly describe the role of dystrophin within the motor unit.