VIII. Types of Skeletal Muscle Fibers

1
VIII. Types of Skeletal Muscle Fibers
2
Categories

• 1. Color varies according the content of
  myoglobin, and oxygen storing, reddish pigment
• a. Red muscles- high myoglobin
• b. White muscle- low myoglobin

3

• 2. Fiber diameter varies as do the cells
  allocations of mitochondria, blood capillaries,
  and sarcoplasmic reticulum
• 3. Contraction velocity and resistance to
  fatigue also differ between fibers

4
(No Transcript)
5
Classes of skeletal muscle fibers

• 1. Slow oxidative (type I) AKA slow twitch
  or fatigue resistance
• a. Have high myoglobin and mitochondria
• b. Split ATP at slow rate but generate a
  lot by aerobic means
• c. Tire slowly so used in postural muscles

6

• 2. Fast oxidative (Type II A) AKA fast
  twitch A or fatigue resistant
• a. High mitochondria and myoglobin
• b. Generate high ATP but split fast as
  well
• c. Contract fast and tire slightly sooner
  than slow twitch

7

• 3. Fast glycolytic (type IIB) AKA fast twitch
  B or fatigable fibers
• a. Low myoglobin and mitochondria
• b. Make ATP by glycolysis and use it fast
• c. Fatigue quickly
• 4. Most muscles contain a mixture but one
  unit will have only one type
• 5. Can alter characteristics through exercise
  but will not change the number of fibers

8
C. Anabolic steroids

• 1. Use can increase size strength and
  endurance of muscles
• 2. Have serious and life threatening results
  though