13. Fiber Types Flashcards
What properties are used to classify muscle fibers?
Metabolic and contractile properties
Name the 3 types of muscle fibers?
- Slow oxidative
- Fast oxidative glycolytic
- Fast glycolytic
What does myosin ATPase activity measure?
Rate at which muscle can contract & break cross bridges
What is a type I fiber?
Slow fibers
What is a type II fiber?
Fast fibers
What do fast and slow fibers look like in basic (routine) pH?
- Fast = dark
- Slow = light
What does myosin ATPase activity measure?
-Rate at which muscle can contract break cross bridges
What do fast and slow fibers look like in basic (routine) pH?
- Fast = dark
- Slow = light
When fiber typing, what does the intensity of staining used to measure?
Activity of various enzymes in the muscle
What enzymes are muscle cross sections stained for? What does each reveal about the fiber?
- Myosin ATPase = fast vs. slow
- Succinate Dehydrogenase = oxidative
- Glycerol phosphate dehydrogenase = glycolytic
What enzymes are muscle cross sections stained for? What does each reveal about the fiber?
- Myosin ATPase = fast (high) vs. slow (low)
- Succinate Dehydrogenase = oxidative
- Glycerol phosphate dehydrogenase = glycolytic
Name the myosin heavy chain isoforms found in mammalian skeletal muscle. Which ones are found in human skeletal muscle?
MAMMALS: -Slow = I -Fast = IIa, IIb, IIx HUMANS: -Slow = I -Fast = IIa, IIx
What is a hybrid fiber?
Can express multiple types of MHC
What is the relationship between mitochondrial content and oxidative capacity?
More mitochondria = higher oxidative capacity
What is the relationship between mitochondrial content and oxidative capacity?
More mitochondria = higher oxidative capacity
What is the relationship between the type of MHC expressed and the metabolic phenotype of a muscle fiber?
- Type I = SO
- Type IIa = FOG
- Type IIx = FG
What is the probability in humans that a muscle fiber will change from expressing slow to fast MHC following normal training?
Very low
“Athletes are born, not made.”
-Genetic variability = certain people have a certain fiber type distribution that predisposes them to be good at certain sports/events
What is the probability in humans that a muscle fiber will change from expressing slow to fast MHC following normal training?
Very low
What determines characteristics of a muscle fiber?
Proteins that are expressed in the muscle fiber
What determines the proteins expressed in a muscle fiber?
Motoneurons that innervate them and their activity patterns
