What type of muscle fibers are responsible for muscle contractions?

Extrafusal muscle fibers are the primary type of muscle fibers responsible for muscle contractions, specifically in skeletal muscles. These fibers are the ones that generate the force for muscle contractions when activated by motor neurons. They are located outside the spindle (the sensory receptor) and are the most common type of muscle fibers found in the musculature of the body.

These fibers are large, striated, and arranged in a parallel fashion, allowing them to effectively contract and produce movement when there is a neural stimulus. In contrast, intrafusal fibers are found within muscle spindles and are primarily involved in proprioception, monitoring changes in muscle length rather than contributing to actual muscle contractions. Cardiac muscle fibers are specialized for the heart and have a different structure and function, while myogenic refers to muscle contraction originating from the muscle itself rather than neural stimulation, which is not specifically related to the type of muscle fibers that cause contraction in skeletal muscles. Thus, extrafusal fibers play a crucial role in voluntary movement and force generation in the body.