Our bodies could not accomplish half the things they are able to if it weren’t for our muscles. There are three distinct types of muscles; Visceral muscle, Cardiac muscle, and Skeletal muscle. Today I will be focusing on the anatomy of Skeletal muscle. This is the only voluntary type of muscle, we are able to consciously control it, unlike visceral and cardiac muscle. The main function of skeletal muscle is to contract so that we are able to move. Most of these muscles are attached to two bones and travel across a joint. These skeletal muscles are formed by small progenitor cells, they are lumped together to form straight, long multinucleated fibers. These fibers are very strong and are striated, meaning they are bundled together.
Like I said before, skeletal muscles are attached to two different bones through tough bands of dense connective tissue called tendons. Because of these tendons, muscle can firmly be attached to bone. The only way muscles can move is by pulling on the tendon, causing the muscle to shorten in length. This brings the bones closer together, one of them staying stationary as the other moves, resulting in movement. The origin is located on the stationary bone, this is where the tendons connect to the bone. The insertion is the point where the tendons connect on the moving bone. The muscle between the two bones is the part that actually contracts.
Muscles begin to contract once they are stimulated by their motor neurons. The motor end plate contains ion channels that open in response to being stimulated, this allows positive ions to ender the muscle fiber. These positive ions actually go through a process and end up opening up even more ion channels in the sarcolemma and T-tubules.