Author Question: Describe a motor unit. How many fibers does a motor unit contain? ... (Read 109 times)

strangeaffliction · **on:** Feb 28, 2019

Describe a motor unit. How many fibers does a motor unit contain?

Question 2

A hypothetical genetic disease causes the body to produce antibodies that compete with acetylcholine for receptors on the motor end plate. Patients with this disease exhibit varying degrees of muscle weakness in the affected muscles. If you could administer a drug that inhibits acetylcholinesteras e or a drug that blocks acetylcholine, which one would you use to alleviate these symptoms?

jjorrostieta · **Reply #1 on:** Feb 28, 2019

Answer to Question 1

A motor unit consists of all of the skeletal muscle fibers controlled by a single motor neuron. They may have as few as 10 fibers (eye muscles) or as many as 10,000 (back muscles).

Answer to Question 2

This is a case of competition between acetylcholine and the antibody. To make the patient's acetylcholine more effective, a drug that inhibits acetylcholinesteras e would slow the breakdown of acetylcholine, relieving some of the weakness. An acetylcholine blocker would be worse than doing nothing.