Types of Skeletal Muscle Fibers

The differences among these groups reflect differences in the way they obtain _______ to support their contractions

ATP

Skeletal muscles containing slow muscle fibers have more extensive network of _______ than do muscles dominated by fast muscle fibers.

capillaries -means there is greater blood flow and the red blood cells can deliver more oxygen to the active muscle fibers

anaerobic glycolysis

fast fiber contractions are supported primarily by this

The three major types of skeletal muscle fibers

fast, slow , and intermediate

slow fibers are red because they contain red pigment __________

myogoblin

Slow fibers (red fibers)

-about half the diameter of fast fibers and take three times as long to contract after stimulation -specialized to continue contracting for extended periods of time, long after a fast fiber would've fatigued -mitochondria able to produce ATP throughout contraction unlike fast fibers; more mitochondria then fast fibers

Intermediate fibers

-contract faster than slow fibers but slower than fast fibers -histologically similar to fast fibers, but have more mitochondria, slightly increased capillary supply, and greater resistance to fatigue

Fast fibers (white fibers)

-large in diameter -contain densely packed myofibrils -large glycogen reserves -relatively few mitochondria -can contract in 0.01 seconds or less following stimulation (most skeletal muscle fibers)

myogoblin

-structurally related to hemoglobin -binds oxygen molecules -contain substantial oxygen reserves that can mobilize during contraction