It is only when our body muscles begin to ache terribly that we realize body has so many muscles. The muscular system is a vast network of tissues, which are attached to the skeletal framework of the body, with the help of nonelastic cords called tendons. They form about 40% of one's body weight and are responsible for controlling the movements of the body.
The human body comprises over 630 muscles, of which the largest (gluteus maximus) is found in the buttocks. The muscles can be categorized further. The muscular system comprises three different types of muscles: skeletal, smooth, and cardiac muscles.
These muscles are also called voluntary muscles, because their movements can be controlled by us. For example, we can choose to raise our hand and pat somebody's shoulder, walk, run, swim, etc. Movements like chewing, blinking, typing, throwing, etc. are all brought about by these voluntary muscles.
Smooth or Involuntary Muscles
Smooth muscles on the other hand, are involuntary muscles that are found lining the intestinal walls, stomach, lungs and other hollow organs. The movements of these muscles cannot be controlled by us, instead they are controlled by the autonomous nervous system.
For example, we cannot control the peristaltic movement of food in the stomach, etc. Neither can we control the movement of the lung muscles and so on.
As the name implies, cardiac muscles are muscles lining the heart and are not found in any other part of the body. They are controlled by the sinus node, which is also influenced by the autonomous nervous system.
Cardiac muscles are less striated as compared to striated muscles and house several mitochondria for energy production. They also feature an extensive network of blood vessels, which supply oxygen to the muscles.
Functions of the Muscular System?
The skeletal framework of our body is covered by muscles whose primary function is providing mobility to the body. These muscles work in pairs (antagonist and agonist muscles) and can only pull and not push. So, to achieve the required function/action, one muscle in the pair pulls the bone and the other pulls it in the opposite direction.
When one wants to move from one place to another, the central nervous system instructs the muscle fibers to contract or relax, thereby conducting the necessary movement which is voluntary. Actions such as walking, climbing, running, lifting, dancing, jogging, etc. are the result of voluntary muscular contractions and relaxations.
We owe our ability to communicate to these skeletal muscles as well, which enable us to speak and write. Being voluntary, these muscles can be controlled by our brain and told what to say and write.
So the next time you say something nasty or insensitive, remember you are in control of your tongue and every word spoken can be controlled by your brain. So get a grip of your tongue and think before you speak!
Maintenance of Posture
We rarely give a thought to how our bodies are able to remain in standing or sitting position. In fact, most of us think that our bodies are at a state of rest during these phases. However, even during these times, certain muscles in the body are constantly contracting and relaxing, making various tiny adjustments, so that your posture can be maintained.
Thus, we are able to continue sitting or standing, due to the contraction of muscles. The muscles of the body also provide joint stability, by extending their tendons over the joints.
Carries out Digestion
The action of stuffing our mouth with food is voluntary and we also have control of the chewing motion. However, once the food is swallowed what happens to it? We do not have any control of it, once it passes down the food pipe or esophagus. The food travels via the esophagus to the stomach via an involuntary muscular movement called peristalsis.
The smooth muscles contract and relax and allow the food ingested to be churned in the stomach and then the intestines. As the digestion process continues, the waste is sent to the rectal region from where it is discarded.
Since we are warm blooded, a constant body temperature ought to be maintained in the body, via temperature regulation. In order to maintain a constant body temperature, the body needs to produce heat. When muscles contract to cause the bones to move, heat is generated. The muscles are responsible for production of almost 75% of body heat requirement.
Thus, in situations wherein the body temperature plummets, the muscles involuntarily contract and generate heat. This is why when we are cold, we find our body shivering. Shivering is the body's mechanism of muscle contraction to generate heat.
Similarly, when the body temperature escalates after exercise or strenuous activity, the muscles redirect the heat to the skin to cool down the body.
The cardiac muscles in the heart are responsible for blood circulation within the heart and its pumping to the rest of the body. The elaborate blood vessel network ensures adequate oxygen is made available to these muscles whose contraction and relaxation movements, are vital for the survival of a person.
Respiration involves inhalation of oxygen-rich air and exhalation involves expulsion of carbon-dioxide-rich air. For this process to take place, the diaphragm muscle is required, which contracts and relaxes to bring about the required inhalation and exhalation.
The muscular network of the body forms a padding for the skeletal framework, thereby protecting the vital internal organs. Moreover, the agonist and antagonist muscles that work in pairs, help slow down the movements of joints in the opposite direction, by contracting.
These muscles are seen to contract to absorb impact from forceful actions like that during sports activities or during a fall.
The muscular system is a truly fascinating organ system of our body. The muscles keep working all the time, even when we are sleeping. It is only when an individual becomes unconscious, that the body is in a complete state of muscular rest. Otherwise, the muscles are always contracting and relaxing.