The muscles in the body provide the means of all movements. They cover the skeletal framework and also give shape to the body. Muscles help to maintain body posture while sitting, standing or walking. Most muscles are long bundles of contractiletissue. Each muscle usually has two ends - a fixed end where the muscle originates and a movable end which pulls some other part. This movable end is drawn out to form a tough structure the tendon which is attached to the bone. When stimulated by a nerve the muscle contracts to become shorter and thicker and thus it pulls the bone at the movable end. Muscles can only contract and relax, they cannot lengthen.
• There are muscles in the root of your hair that give you goose bumps.
• It takes 17 muscles to smile and 42 muscles to frown.
• The hardest working muscle is in eye.
Muscles often work in pairs which work against each other. These are called antagonistic pairs. The muscles in the upper arm control the bending and straightening of the arm. The two muscles, the biceps and triceps are working against each other. When the biceps contracts the lower arm is raised and the arm bends. In this position the triceps muscle is relaxed. To straighten the arm the reverse happens. The triceps contracts straightening the arm, while the biceps relaxes. Antagonistic muscles can be found all over the body. In the iris of the eye there are two sets of muscle. There are radial muscles which radiate from the pupil like spokes of a bicycle and there are circular muscles. The radial muscles make the pupil of the eye wider, while the circular muscles make the pupil smaller.
Measure the size of your biceps and also ask your friends to do. Take turns lifting a bottle with water as many times as you can. Record the number of lifts each student was able to do. Compare each pair’s results with the rest of the class and determine whether those with larger bisceps were able to do more lifts.
Types of Muscles
Muscles found in higher vertebrates are of three types:
* Striated or skeletal muscles or voluntary muscles.
* Unstriated or smooth muscles or involuntary muscles
* Cardiac muscles
Coordination of Muscles
Most actions in our body like standing, walking, running, playing tennis etc. , require combined action of several muscles. To a great extent the muscles have to be coordinated for a particular kind of movement.
Muscles move body parts by contracting and then relaxing. Muscles can pull bones, but they can't push them back to the original position. So they work in pairs of flexors and extensors. The flexor contracts to bend a limb at a joint. Then, when the movement is completed, the flexor relaxes and the extensor contracts to extend or straighten the limb at the same joint. For example, the biceps muscle, in the front of the upper arm, is a flexor, and the triceps, at the back of the upper arm, is an extensor. When you bend your elbow, the biceps contracts. Then the biceps relaxes and the triceps contracts to straighten the elbow.