When we think of muscles contracting, we often picture the muscle itself shortening and bulging, but do you know which point of attachment is actually being pulled?
To understand this, we first need to know a little bit about muscle anatomy. Muscles are made up of bundles of muscle fibers, which in turn are made up of even smaller myofibrils. These myofibrils contain two kinds of protein filaments – thick filaments made of myosin and thin filaments made of actin.
When a muscle contracts, the myosin and actin filaments slide past each other, causing the muscle fibers to shorten. But in order for this to happen, one end of the muscle must be anchored to a fixed point, while the other end is free to move. The point of attachment that is pulled during muscle contraction is called the insertion.
The insertion is the point where the muscle attaches to the bone that it is responsible for moving. For example, if we look at the bicep muscle in our arm, the insertion is on the radius bone in our forearm, while the origin is at the scapula in our shoulder. When the bicep contracts, the insertion on the radius is pulled towards the origin at the scapula, causing the forearm to bend towards the bicep.
It`s important to note that not all muscles have fixed points of attachment. Some muscles, like the diaphragm in our chest, have one end attached to a muscle or bone, while the other end is free and moves with the contraction.
In summary, the point of attachment that is pulled during muscle contraction is called the insertion, which is the point where the muscle attaches to the bone that it is responsible for moving. Understanding muscle anatomy and function can help us better understand how our bodies move and function.
