Muscle atrophy?

[swtiepie711]

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Q53 of the sample items provided by NBME has a question about a woman in a cast & what characterizes her muscle "at this time."
A) Conversion to fast fibers
B) Decrease in number of fibers
C) Decrease in number of myofibrils
D) Increase in mitochondria
E) Increase in number of satellite cells

Answer: C

I can't seem to find this anywhere. I knew it was muscle atrophy, but that can be loss of intracellular organelles/etc or actual cell loss - according to the answer, seems that muscle atrophy doesn't mean actual loss of muscle fibers. Is this true? I have googled, looked & can't seem to find anything that states clearly one way or the other. Thanks for any clarification or if you know where I should go to find the answer 🙂

 

[perilou]

Q53 of the sample items provided by NBME has a question about a woman in a cast & what characterizes her muscle "at this time."
A) Conversion to fast fibers
B) Decrease in number of fibers
C) Decrease in number of myofibrils
D) Increase in mitochondria
E) Increase in number of satellite cells

Answer: C

I can't seem to find this anywhere. I knew it was muscle atrophy, but that can be loss of intracellular organelles/etc or actual cell loss - according to the answer, seems that muscle atrophy doesn't mean actual loss of muscle fibers. Is this true? I have googled, looked & can't seem to find anything that states clearly one way or the other. Thanks for any clarification or if you know where I should go to find the answer 🙂

It makes sense that it wouldn't be loss of actual myocytes, because they are differentiated tissue which cannot regenerate (and therefore, you would be permanently atrophied). When you exercise, your muscles undergo hypertrophy (not hyperplasia).

Disuse atrophy just decreases the enzymes and actin/myosin.

 

[Jccripe]

muscle fibers are muscle cells. and Myofibrils are sarcomeres in series inside a cell. Atrophy is loss of cell size due to decreased organelles and proteins which include myofibrils/sarcomeres. If this is not making sense just imagine the exact opposite of hypertrophy which is addition of sarcomeres/myofibrils which make your muscle cells huge...

 

[swtiepie711]

muscle fibers are muscle cells. and Myofibrils are sarcomeres in series inside a cell. Atrophy is loss of cell size due to decreased organelles and proteins which include myofibrils/sarcomeres. If this is not making sense just imagine the exact opposite of hypertrophy which is addition of sarcomeres/myofibrils which make your muscle cells huge...

I get what you guys are saying - I guess I got confused by the fact that in Goljan he says atrophy can be loss of organelles OR loss of cells (in the intro chapter)... Thanks for the replies

 

[BoneNibbler]

I get what you guys are saying - I guess I got confused by the fact that in Goljan he says atrophy can be loss of organelles OR loss of cells (in the intro chapter)... Thanks for the replies

Yes atrophy can be both. MUSCLE atrophy can only be the former.👍

 

[swtiepie711]

Yes atrophy can be both. MUSCLE atrophy can only be the former.👍

Many thanks! 🙂