Chapter 13, Problem 1.1BGL

Summary Introduction

To label: The different types of muscle fibers given in Figure 13.1.

Introduction: Muscles are composed of a group of muscle fibers. Fibers of skeletal muscles are classified into three types based on the speed of contraction and the mode of ATP production. They are slow oxidative (SO), fast oxidative (FO) and fast glycolytic (FG).

Answer to Problem 1.1BGL

Pictorial representation:

Fig1: The different types of muscle fibers: slow oxidative, fast glycolytic, and fast oxidative glycolytic fibers

Explanation of Solution

The SO fibers contract gradually as well as use aerobic metabolism for the production of ATPs. Thus, the fatigue rate is low. Fast fibers contract at a faster rate and use aerobic and anaerobic metabolisms for the production of ATPs. Thus, they rapidly fatigue.

1. Slow oxidative fibers: The diameter of these fibers is small than other types of fibers. High content of myoglobin is present. Numerous mitochondria and blood capillaries are present in this group. These fibers appear red in color.

2. Fast glycolytic fibers: These fibers are large in size and so they possess the largest diameter. These fibers contain relatively low levels of myoglobin. These fibers possess less number of mitochondria and blood capillaries. They appear in pale white color.

3. Fast oxidative-glycolytic fiber: The diameter of these fibers is greater than slow fibers and lesser than the fast glycolytic fibers. These fibers contain a large amount of myoglobin content. Numerous mitochondria and blood capillaries are present in this group. They appear in pink or red color.