13. Fiber Types

Question 1

What properties are used to classify muscle fibers?

Answer 1

Metabolic and contractile properties

Question 2

Name the 3 types of muscle fibers?

Answer 2

• Slow oxidative
• Fast oxidative glycolytic
• Fast glycolytic

Question 3

What does myosin ATPase activity measure?

Answer 3

Rate at which muscle can contract & break cross bridges

Question 4

What is a type I fiber?

Answer 4

Slow fibers

Question 5

What is a type II fiber?

Answer 5

Fast fibers

Question 6

What do fast and slow fibers look like in basic (routine) pH?

Answer 6

• Fast = dark

- Slow = light

Question 7

What does myosin ATPase activity measure?

Answer 7

-Rate at which muscle can contract break cross bridges

Question 8

What do fast and slow fibers look like in basic (routine) pH?

Answer 8

• Fast = dark

- Slow = light

Question 9

When fiber typing, what does the intensity of staining used to measure?

Answer 9

Activity of various enzymes in the muscle

Question 10

What enzymes are muscle cross sections stained for? What does each reveal about the fiber?

Answer 10

• Myosin ATPase = fast vs. slow
• Succinate Dehydrogenase = oxidative
• Glycerol phosphate dehydrogenase = glycolytic

Question 11

What enzymes are muscle cross sections stained for? What does each reveal about the fiber?

Answer 11

• Myosin ATPase = fast (high) vs. slow (low)
• Succinate Dehydrogenase = oxidative
• Glycerol phosphate dehydrogenase = glycolytic

Question 12

Name the myosin heavy chain isoforms found in mammalian skeletal muscle. Which ones are found in human skeletal muscle?

Answer 12

MAMMALS:
-Slow = I
-Fast = IIa, IIb, IIx
HUMANS:
-Slow = I
-Fast = IIa, IIx

Question 13

What is a hybrid fiber?

Answer 13

Can express multiple types of MHC

Question 14

What is the relationship between mitochondrial content and oxidative capacity?

Answer 14

More mitochondria = higher oxidative capacity

Question 15

What is the relationship between mitochondrial content and oxidative capacity?

Answer 15

More mitochondria = higher oxidative capacity

Question 16

What is the relationship between the type of MHC expressed and the metabolic phenotype of a muscle fiber?

Answer 16

• Type I = SO
• Type IIa = FOG
• Type IIx = FG

Question 17

What is the probability in humans that a muscle fiber will change from expressing slow to fast MHC following normal training?

Answer 17

Very low

Question 18

“Athletes are born, not made.”

Answer 18

-Genetic variability = certain people have a certain fiber type distribution that predisposes them to be good at certain sports/events

Question 19

What is the probability in humans that a muscle fiber will change from expressing slow to fast MHC following normal training?

Answer 19

Very low

Question 20

What determines characteristics of a muscle fiber?

Answer 20

Proteins that are expressed in the muscle fiber

Question 21

What determines the proteins expressed in a muscle fiber?

Answer 21

Motoneurons that innervate them and their activity patterns