What are muscles primarily composed of?

Muscles are primarily composed of long cells, known as muscle fibers, that have the unique ability to contract when stimulated. This contraction is facilitated by complex interactions between proteins such as actin and myosin within the muscle fibers. When a muscle fiber receives a signal from the nervous system, it triggers a series of biochemical reactions that lead to contraction, enabling movement of body parts. This characteristic is what distinguishes muscle tissue from other types of tissues in the body, such as connective or adipose tissue, which serve different functions.

The ability of muscle fibers to contract and produce motion is essential for various bodily functions, including locomotion, posture maintenance, and even involuntary actions such as heartbeats and digestion. Understanding this fundamental aspect of muscle anatomy and physiology is crucial for applying knowledge in nutrition and fitness contexts, as it relates directly to how the body utilizes nutrients for energy and recovery during physical activities.