Answer:
muscle fibers
Explanation:
Muscle tissue is responsible for the movement of organisms and their organs. It is formed by cells called myocytes or muscle fibers.
The contractile or extrafusal muscle fibers are the characteristic cells of the muscle. They are multinucleated cells, large and very elongated, measuring from a few millimeters to 30cm in length.
Muscle fibers have individual characteristics that give them a certain specialization, and although they combine modalities of speed, power and endurance, in general one of them predominates over the others.
In their cytoplasm they contain a precise organization of contractile proteins called myofibrils. These myofibrils are responsible for changes in muscle fiber length when they contract or relax.
There are three types of muscle fibers that differ in color, metabolism and functional properties:
- Type I fibers (red fibers): they are reddish-looking fibers due to their richness in myoglobin (important for the transport of oxygen within the muscle cell) and are characterized by being slow contraction, developing little strength and being very resistant to fatigue .
- Type IIb fibers (white fibers): they are fibers of large diameter and whitish appearance due to their lower amount of myoglobin; Their contraction is rapid and they develop a lot of strength, but they tire quickly.
- Type IIa fibers (mixed fibers): they are fibers of appearance and intermediate properties between the other two. The contraction is rapid, but they have some resistance to fatigue.
