Subsequent to motor neuron degeneration in Charcot-Marie-Tooth disease, muscles begin to weaken and degenerate as well. What is the likely cause?

Question

  Charcot-Marie-Tooth is the most commonly inherited peripheral neuropathy, and has no known cure. Patients suffer damage to motor and sensory neurons, leading to degeneration of muscles and gradual loss of motor control.

A.  Muscles will atrophy if they don't receive regular stimulation from motor neurons.
B.  Muscles require healthy Schwann cells for myelination as well.
C.  Muscles contain large numbers of mitochondria.
D.  Toxins leak out from the dying motor neurons onto the muscles.

Clarify Question
· What is the key concept addressed by the question?
· What type of thinking is required?

Gather Content/Choose Answer
· What do you already know about components of the nervous system? What other information is related to the question?

Reflect on Process
· Did your problem-solving process lead you to the correct answer? If not, where did the process break down or lead you astray? How can you revise your approach to produce a more desirable result?

Answer 1

A.  Muscles will atrophy if they don't receive regular stimulation from motor neurons.

Clarify Question
· What is the key concept addressed by the question?
        o The question is asking you to evaluate the cause of muscle degeneration following motor neuron degeneration in Charcot-Marie-Tooth disease.
· What type of thinking is required?
        o This question is asking you to evaluate the cause of muscle degeneration in Charot-Marie-Tooth disease following motor neuron degeneration.

Gather Content/Choose Answer
· What do you already know about components of the nervous system? What other information is related to the question?
        o To solve this problem, you’ll need to apply your knowledge of what happens to muscles when they are inactive for long periods of time and the cause of Charcot-Marie-Tooth disease. Although not discussed directly in this chapter, you are probably aware that muscles atrophy and weaken when they are not used. Charcot-Marie-Tooth disease produces a loss of motor neurons and/or their function. As motor neurons control muscle contraction, if motor neurons degenerate, then muscles with atrophy over time. Thus, the answer is a.

Reflect on Process
· Did your problem-solving process lead you to the correct answer? If not, where did the process break down or lead you astray? How can you revise your approach to produce a more desirable result?
        o If you figured out the correct answer, good job! If not, where did you go wrong? Did you remember that motor neurons control muscles? Did you forget that fMRI is a brain scanning technique and EKG a heart monitoring technique? While muscles can contain large numbers of mitochondria, and Charcot-Marie-Tooth disease can be caused by clumping of mitochondria in motor neurons, the question does not provide information that states that such clumping occurs in muscle cells.