Muscles contract by a motor neuron being activated. This produces an action potential that passes outward in a ventral root of the spinal cord where it is conveyed to a motor end plate on each muscle fiber. The action potential causes the release of packets of acetylcholine into the synaptic clefts on the surface of the muscle fiber. The acetylcholine causes the electrical resting potential under the motor end plate to change, and this then initiates an action potential which passes in both directions along the surface of the muscle fiber. At the opening of each transverse tubule onto the muscle fiber surface, the action potential spreads inside the muscle fiber. At each point where a transverse tubule touches part of the sarcoplasmic reticulum, it causes the sarcoplasmic reticulum to release Ca+2 ions. The calcium ions result in movement of troponin and tropomyosin on their thin filaments, and this enables the myosin molecule heads to "grab and swivel" their way along the thin filament. This is muscle contraction.
Body muscles of human beings are controlled by a system which is called as nervous system. A medical explanation, a nervous system comprises of brain and spinal cord, both of them control the movement or you can say the contraction of the muscles. Brain and spinal cord both perform nearly same functions i.e. Muscle contraction but it's the brain that control intentional muscle movements and the spine controls the unintentional movements. If we closely look at its procedure than we will analyze that brain is the most important organ in the body of human beings and it's the brain which sends signals or instructions through which muscles react. There are some movements where instructions are not sent by the brain but on the other hand through spinal cord definitely. There are three types of muscle tissues: 1) Skeletal muscles. 2) Cardiac muscles. 3) Smooth muscles. Skeletal muscles and cardiac muscles resemble a lot because their physical appearance apart from functions under microscopic examination is more likely to each other. Medical practitioners stress a lot about daily exercise because it help muscles to keep moving and active but special exercise must have to be conducted under the supervision of some experts because any wrong movement may damage muscles.
The human anatomy is truly a marvel. It is made up of a number of small and major parts that work in sync, as a system and mechanism. One of the vital components of this unique mechanism is the muscles. The skeleton is covered with muscles and tissues. While the skeleton forms the framework, the muscles give shape and function as the engine!
Muscles turn energy into motion. The body movements are possible only because of the co-ordination of the muscles. Muscles are sophisticated, long-lasting and self healing components of the anatomy. They expand and contract as per the requirement of the body, in accordance to the co-ordination expected in response to stimuli. Contraction takes place due to the mutual sliding of the two sets of filaments. The filaments are either thick or thin. The thick filament contains protein myosin, while the thin filament contains protein actin. The sliding of the thick and thin filament takes place due to 'cross bridges'. Cross bridges are parts of myosin molecules that stick out from the myosin filaments. They interact cyclically with the thin filaments, resulting in the intended movement.
The expansion and contraction of muscles are essential for body posture, joint stability and the production of heat in the body. The body would never be able to function without muscles.
