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The Human Body:
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Muscles
There are over 600 muscles in the body and they make up to 40% of the total body weight. Muscles aid people in enabling them to move, conduct different body positions and to translate facial expressions and body language. Muscles are made of fibers. Each fiber consists of thickly packed long, thin cells. The fibers are all bundled into bundles and are wrapped in a sheath of tissue called the perimysium. The muscles are separated from the sheath of tissue called the deep fasica. They are made from 2 proteins, the myosin and the actin.
Most of the muscles are used to move bones of the skeleton and are so, known as the skeletal muscles. Each one is attached to a bone at one end and a different bone at the other by flexible chains called the tendons. Nerves run along the muscles and carry messages to and forth the brain and the muscles.
Muscles come in different shapes. The spindle shaped muscles having a thick middle section and taper off at the ends. They often have 2 or more cords and includes the biceps and triceps in the upper arm. There are also flat muscles located in the forehead or the abdomen. The other type is called the triangular muscles which include the deltoid muscles which enables the arm to be raised. Lastly, the circular/rind-shaped muscles which surround the eyes and mouth, or acts as sphincters which either relaxes and contracts to release substances.
There are the voluntary muscles and the involuntary muscle. Each has their fair share of work to maintain the body’s activities. Skeletal muscles belong to the voluntary muscles as they are controlled by the conscious part of the brain. The muscles that keep working all the time are the involuntary muscles which are also controlled by the brain without conscious control. The involuntary muscles work to expand one’s chest and draw air into the lungs to provide the body with a sound amount of oxygen for its activities. The heart, which is a big piece of muscle, pumps blood around the body continuously. This is also the same for the digestive system, whereby the muscles work all the time to allow the body to receive it’s neede nutrients.
Muscles work in pairs. One pulls on the bone attached to it by contracting and the other relaxes. A muscle contraction occurs in 3 phases-latent, contraction and relaxation. The latent phase is the time between the message leaving the brain and the muscles actually contracting. The contraction phase is the time taken for the muscle to contract. The last, the relaxation phase is the time needed for the muscle to return to its original position. Muscles derive their energy to work from glucose and it has its own glucose store-glycogen. It is usually used first prior to consuming the circulating ones.
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