Lihassäieet
Lihassäieet, also known as muscle fibers, are the fundamental cellular units of muscle tissue in vertebrates and invertebrates. These elongated cells are specialized for contraction, enabling movement. In vertebrates, lihassäieet are multinucleated, meaning they contain multiple nuclei within a single cell membrane. Each lihassäie is filled with myofibrils, which are long, rod-like structures composed of repeating protein filaments, primarily actin and myosin. The arrangement of these filaments creates a characteristic striated appearance in skeletal and cardiac muscle, hence the term "striated muscle."
There are several types of lihassäieet, broadly categorized into slow-twitch (Type I) and fast-twitch (Type II)
The contraction of lihassäieet is triggered by a nerve impulse at the neuromuscular junction. This signal leads