Which of the following apply to Type IIB fibers (fast twitch glycolytic)? 1) little myoglobin 2) lots of myoglobin 3) mainly uses aerobic cell respiration for energy 4) quick to fagigue
The correct answer and explanation is:
The correct answer is:
- little myoglobin
- quick to fatigue
Type IIB fibers, also known as fast-twitch glycolytic fibers, are specialized for rapid and intense movements but have distinct metabolic characteristics. Here’s an explanation of why the answers are what they are:
- Little Myoglobin: Type IIB fibers have a relatively low myoglobin content. Myoglobin is a protein that helps store oxygen in muscle cells, and its presence is usually associated with aerobic (oxygen-dependent) muscle fibers. Since Type IIB fibers primarily use anaerobic metabolism (glycolysis), they don’t rely much on myoglobin, unlike slow-twitch fibers (Type I), which have more myoglobin to support sustained, endurance activities.
- Quick to Fatigue: These fibers are designed for short bursts of powerful activity, such as sprinting or lifting heavy weights. However, they fatigue quickly because they generate energy mainly through anaerobic processes, which are less efficient and lead to the accumulation of lactic acid. This limits the amount of time they can sustain activity before fatigue sets in.
In contrast to Type IIB fibers, Type I fibers are more endurance-oriented, have lots of myoglobin, and are slower to fatigue due to their reliance on aerobic metabolism. Type IIA fibers are a hybrid between Type I and Type IIB fibers, possessing some characteristics of both.
To summarize, Type IIB fibers are fast-twitch and glycolytic, meaning they rely on glucose for energy rather than oxygen, leading to their rapid fatigue and lower myoglobin content.