The Human Muscular System
In humans, around half the body weight is part of the muscular system. Instead of losing weight, we at times gain weight even after training. The weight that we gain is known as muscle weight.
The force that we generate for moving the body is provided by the muscles. Muscles are connected to the joints and the bones. Muscles react to the nerve impulses because they work in groups.
Muscles are of three types: Skeletal muscle, Smooth muscle and Cardiac muscle.
1) Skeletal muscle:
In a human body, there are around six hundred and fifty skeletal muscles which are attached to the skeleton. Skeletal muscles are also known as voluntary muscles because they are not directly controlled by the nervous system. Skeletal muscles work in tandem that is, they help in moving the bones back and forth. Contraction of muscles can be long, single or short.
2) Smooth muscle:
In the internal organs of a human body smooth muscles are found. Smooth muscles are found in the respiratory system, blood vessels, bladder and the digestive system. In females, the smooth muscles are also found in the uterus. For a long time, the smooth muscles can remain stretched and it can maintain the tension. Smooth muscles are automatically controlled by the nervous system hence they are known as involuntary muscles.
3) Cardiac muscle:
In the heart of a human body cardiac muscles are found. Just like smooth muscles, the cardiac muscles can stretch. The cardiac muscles can also contract, just like skeletal muscles. Cardiac muscle can only have single or short contraction and this is why it is known as twitch muscle. Just like smooth muscles, cardiac muscles are also automatically controlled by the nervous system hence they are known as involuntary muscles. Our heart would stop beating if the cardiac muscles were voluntary.