Muscular System

What are the Parts of the Muscular System?

There are two main types of muscle:(1) Skeletal Muscles and (2) smooth muscles. A third kind of muscle, called cardiac muscle,has characteristics of both skeletal and smooth muscles but is found only in the heart. All muscles are made up of cells called connective tissue. Skeletal muscle fibers have bands called straitens. Each fiber also has many core elemants called nuclei. Smooth muscles have no straitens and only one nucleas in each fiber. Cardiac muscles have straitens and a single nucleas in each fiber. Muscle fibers are held together by connective tissue
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Skeletal muscles- help hold the bones of the skeleton together and give the body shape. They also make the body move. Skeletal muscles make up a large part of the legs, arms, abdomen, chest, neck, and face. All muscles are made up of cells called fibers. Skeletal muscle cells have thousands of long, cylindrical muscle fibers. Muscle fibers are held together by connective tissue.

Cardiac muscle- has traits of both the skeletal muscle and the smooth muscle. Cardiac muscles have have straitens like the skeletal muscle and one nucleas like the smooth muscle. Cardiac muscles are only found in the heart. When caridiac muscles contract, they push blood out of the heart and into the arteries.  The heart also contains a group of specailized cells called sinoatrial node, or S-A node. The S-A node starts up each contraction of the cardiac muscle by giving off rythmic signals to neighboring muscle cells. As these cells contract, they cause others to cotract aswell. By this process, all the caridiac muscles contract together. The autonomic nerves that stimulate the S-A node control how often the cardiac muscle contracts. The S-A node thus acts as a hearts "peacemaker", because it determines how often the heart beats to pump blood through the body.

Smooth muscles- are found in various organs of the body. In order to maintain the needs of the organs that smooth muscles are found in, walls of the stomach, intestines, blood vessels, and bladder, the cells can not be straited. Instead, they need to be able to bend and contract, therefore the cells have only one nucleus and they contract automatically. Smooth muscles operate slowly and automatically in a natural, rythmic pattern of contraction followed by relaxation. In this way, they control various body processes. For examply, the steady process of smooth muscles in the stomach and intestines moves food along for digestion. Because they are not under consious control by the brain, smooth muscles are also know as involuntary muscles.

Major muscles:

  • In each of your shoulders is a deltoid (say: del-toyd) muscle. Your deltoid muscles help you move your shoulders every which way — from swinging a softball bat to shrugging your shoulders when you're not sure of an answer.
  • pectoralis (say: pek-tuh-rah-lus) muscles are found on each side of your upper chest. These are usually called pectorals (say: pek-tuh-rulz), or pecs, for short. When many boys hit puberty, their pectoral muscles become larger. Many athletes and bodybuilders have large pecs, too.
  • Below these pectorals, down under your ribcage, are your rectus abdominus (say: rek-tus ab-dahm-uh-nus) muscles, or abdominals (say: ab-dahm-uh-nulz). They're often called abs for short.
  • When you make a muscle in your arm, you tense your biceps (say: bye-seps) muscle. When you contract your biceps muscle, you can actually see it push up under your skin.
  • Your quadriceps (say: kwad-ruh-seps), or quads, are the muscles on the front of your thighs. Many people who run, bike, or play sports develop large, strong quads.
  • And when it's time for you to take a seat? You'll be sitting on your gluteus maximus (say: gloot-ee-us mak-suh-mus), the muscle that's under the skin and fat in your behind!

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