HUMAN MUSCLE POWER

                 Muscles make the body  move. All muscles are made up of tiny fibers that can contract, making a muscle shorter so that it pulls on a part of the body.  The largest muscles in the body are connected to the bones. Most of these skeletal muscles are under voluntary control, which means we can move them at will. Other muscles, such as those in the heart and stomach,  are involuntary-they work without us having to think.  Altogether, there are billions of muscles in the human body, including microscopic muscles on every hair and blood capillary.

   Muscular system

                        More than 640 muscles are arranged in crisscrossing layers between the skin and bones of the skeleton. Most are attached to bones by tough fibrous  straps called tendons. Muscles, tendons, and bones work together like a system of levers. For example, when the biceps muscle in the upper arm contracts,  it pulled on the bone in the forearm and bents the arm at the elbow. In this image, muscles lying just under the skin are shown on  one side of the body and deeper muscles are shown on the other.

   Muscle Types

              There are three types of muscles in the body: skeletal, smooth, and cardiac(: heat) muscle. Skeletal muscles are attached to the bones. They are made up of very long thread - like cells that contract powerfully and quickly, for a  short period of time. Smooth muscle occurs in the stomach, intestines,  blood vessels, and ice. It is made up of short, spindle - shaped cells that can contract for longer periods than other type of muscle. Cardiac muscle is found only in the heart. It consists of short muscle cells that contract rhythmically without tiring.

 

      Working In Pairs,

                     Skeletal muscles often work in pairs that pull bones in opposite directions. For example, in the upper arm there are two large muscles: the biceps at the front and triceps at the back. When the biceps contracts, it bends your arm. When the triceps,   contracts,  it straightens the arm.

    Muscle shapes

                  Muscles come in a wide variety of shapes, depending on their  location and role in the body. Some taper to appoint at one or both ends to produce maximum pulling force, where us others have simple strap shapes. Circular  muscles close body openings, such as the mouth and bladder  exit.

     Fibers in 

            Skeletal muscles, such as those in your legs, consist of bundles of muscular cells, cold muscle fibers.  Each cell consists, in tern, of a bundle of smaller, road -shaped fibrous in MYO fibrils, and these are made of even thinner fibers called filaments. The filaments are called the parts that create movement. When triggered by a nerve signal, they slide across each other, interweaving to make the cell shorter. All the cells in the muscle contract at ones to make the whole muscle shorter.

  Thigh muscle

               The four-part muscle called the quadriceps forms the front of the thigh. One of the largest and most powerful muscle in the body,  the quadriceps extends your leg when you walk, run, and jump.