Chapter 10 (Muscular Tissue XI)

Question 1

Types of Skeletal Muscle Fibers

Answer 1

Muscle fibers vary in their content of myoglobin
1- Red muscle fibers
2- White muscle fibers

Question 2

Red muscle fibers

Answer 2

Have a high myoglobin content
Appear darker (dark meat in chicken legs and thighs)
Contain more mitochondria
Supplied by more blood capillaries

Question 3

White muscle fibers

Answer 3

Have a low content of myoglobin
Appear lighter (white meat in chicken breasts)

Question 4

Muscle fibers contract at

Answer 4

Different speeds, and vary in how quickly they fatigue

Question 5

Muscle fibers are classified into three main types

Answer 5

1) Slow oxidative fibers
2) Fast oxidative-glycolytic fibers
3) Fast glycolytic fibers

Question 6

Slow Oxidative Fibers (SO fibers)

Answer 6

Smallest in diameter
Least powerful type of muscle fibers
Appear dark red (more myoglobin)
Generate ATP mainly by aerobic cellular respiration
Have a slow speed of contraction
Twitch contractions last from 100 to 200 msec
Very resistant to fatigue
Capable of prolonged, sustained contractions for many hours
Adapted for maintaining posture and for aerobic, endurance-type activities such as running a marathon

Question 7

Fast Oxidative–Glycolytic Fibers (FOG fibers)

Answer 7

Intermediate in diameter between the other two types of fibers
Contain large amounts of myoglobin and many blood capillaries
Have a dark red appearance
Generate considerable ATP by aerobic cellular respiration
Moderately high resistance to fatigue
Generate some ATP by anaerobic glycolysis
Speed of contraction faster
Example: Twitch contractions last less than 100 msec
Contribute to activities such as walking and sprinting

Question 8

Fast Glycolytic Fibers (FG fibers)

Answer 8

Largest in diameter
Generate the most powerful contractions
Have low myoglobin content
Relatively few blood capillaries
Few mitochondria
Appear white in color
Generate ATP mainly by glycolysis
Fibers contract strongly and quickly
Fatigue quickly
Adapted for intense anaerobic movements of short duration
Example: Weight lifting or throwing a ball