Question

With regard to mitochondrial density, which muscle fiber type has a very small amount of mitochondria?

1) Type I muscle fibers
2) Type IIa muscle fibers
3) Type IIb muscle fibers
4) Type IIx muscle fibers

Answer 1

Type IIb muscle fibers(option 3) have a very small amount of mitochondria, are optimized for short bursts of high-intensity activity, and fatigue quickly.

Step-by-step explanation:

The muscle fiber type with a very small amount of mitochondria is the Type IIb muscle fibers. These fibers are anaerobic, glycolytic 'white' muscle fibers that are less dense in mitochondria and myoglobin compared to other types. Type IIb fibers are optimized for short, intense bursts of activity and tend to fatigue rapidly.

They are primarily used for anaerobic movements that require power for a short duration, such as sprinting or weight lifting. As such, these fibers have large glycogen reserves but do not sustain activity for long due to the quick fatigue without sufficient oxygen and lower mitochondrial density.