The human body consists of three types of muscle tissues: the smooth, the cardiac and the skeletal muscles. The smooth muscles make up the muscle tissues in hollow organs in the body, such as the stomach, gastro-intestinal tract and uterus; The cardiac muscle is located in the heart; and lastly, the skeletal muscles are found attached to bones. To understand the skeletal muscles, here is a simpler explanation about them.
The skeletal muscles are elongated muscular fibers. When you try to look at them under the microscope, you will see cylindrically-shaped cells. The cell is multi-nucleated; meaning, you will see several nuclei even in a single cell. The location of the nucleus is on the side. When you look at the skeletal muscle on a cross-sectional view, you will better appreciate the numerous nuclei found on the side of the fibers. Skeletal muscles are also known as striated muscles. The alternating dark and light bands in the fibers are responsible for the striations. The main proteins that make up the fibers are the actin and the myosin. When the two bind together, muscle contraction commences.
Control of Movement
Unlike the other two types of muscles where they contract even without thinking of it, the skeletal muscle is voluntarily-controlled. In medical terms, the control is by the somatic nervous system. It moves only when you tell it to move. That makes it rationale to say that your arm will stay in its place unless you make it move, while your heart keeps on beating and your stomach contracting even at the absence of your control. However, there are some skeletal muscles that are, at the same time, subconsciously controlled. Even without asking them to contract, they shorten. An example is the diaphragm that causes you to inhale and exhale air, even without consciously controlling it.
Location and Function
You see the striated muscles in parts of your body where there is bone, such the name skeletal muscle. They are responsible for the movement you produce. The individual muscles shorten in the presence of stimulus. The contraction starts when calcium ions begin to leak from the endoplasmic reticulum. Due to the changes in the electrical potential inside and outside of the cell, the muscle fibers begin to shorten. Collectively, they pull the bones to create motion.
Muscle fatigue is a normal phenomenon when your muscles experience too much stress. It happens to protect you from injury. Much as you want to keep on moving, your muscles experience fatigue due to prolonged contraction. In this case, you will have to rest for awhile to protect them from further damages. The causes of fatigue include loss of energy to supply the contraction, depletion of oxygen and accumulation of lactic acid. By giving your muscles time to recuperate, you allow repair to occur; and thus, increase muscle strength.
Skeletal muscles serve several functions. It includes movement and energy generation. Once you understand the anatomy of the structure, you can better comprehend its physiology.