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Muscular System 2018 Muscular System Muscular System Have you ever tried to sit still, without moving any muscles at all, for one minute? It’s impossible! Somewhere in your body, muscles are always working. You use muscles when you eat and breathe. Muscles, along with your skeleton, hold you upright and let you move. If all of your muscles rested at once, you would collapse. The muscular system is made up of the muscles that let you move. Actions of Muscle Some of your body’s movements, such as smiling, are easy to control. Other movements, such as the beating of your heart, are impossible to control completely. That is because some of your muscles are not under your conscious control. Those muscles are called involuntary muscles. Involuntary muscles are responsible for such essential activities as breathing and digesting food. The muscles that are under your conscious control are called voluntary muscles. Smiling, turning a page in a book, and getting out of your chair when the bell rings are all actions controlled by voluntary muscles. Kinds of Muscle Your body has three types of muscle tissue—skeletal muscle, smooth muscle, and cardiac muscle. Some of these muscle tissues are involuntary, and some are voluntary. Below you can see a magnified view of each type of muscle in the body. Both skeletal and smooth muscles are found in many places in the body . Cardiac muscle is found only in the heart. Each muscle type performs specific functions in the body . Skeletal Muscle Skeletal muscles are attached to the bones of your skeleton, skin and fascia and provide the force that moves your bones. At each end of a skeletal muscle is a tendon. A tendon is a strong connective tissue that attaches muscle to bone. Skeletal muscle cells appear banded, or striated with light and dark tissue. For this reason, skeletal muscle is sometimes called striated (STRY ay tid) muscle. Skeletal Muscle Because you have conscious control of skeletal muscles, they are classified as voluntary muscles. One characteristic of skeletal muscles is that they react very quickly. However, another characteristic of skeletal muscles is that they tire quickly. Function in pairs to bring about the co-ordinated movements of the limbs, trunk, jaws, eyeballs, etc Smooth Muscle The inside of many hollow internal organs, such as the stomach, blood vessels, intestines, and urinary bladder contain smooth muscles. Smooth muscles even help your eyes focus. Smooth muscles are involuntary muscles. They work automatically to control certain movements inside your body, such as those involved in digestion. Unlike skeletal muscles, smooth muscle cells are not striated . Smooth muscles behave differently than skeletal muscles, too. Smooth muscles react more slowly and tire more slowly. Smooth Muscle For example, as the smooth muscles of your stomach contract, they produce a churning action. The churning mixes the food with chemicals, and helps to digest the food. The muscle of the arteries contracts and relaxes to regulate the blood pressure and the flow of blood. Cardiac Muscle The tissue called cardiac muscle is found only in your heart. Cardiac muscle has some characteristics in common with both smooth muscle and skeletal muscle. Like smooth muscle, cardiac muscle is involuntary. Like skeletal muscle, cardiac muscle cells are striated. However, unlike skeletal muscle, cardiac muscle does not get tired. It can contract repeatedly. You call those repeated contractions heartbeats. Muscular System Functions of the Muscular System 1. Stabilize joints with their TENDONS 2. Produce movement (including standing upright) 3. Produce heat to maintain body temperature Muscle at Work Like other skeletal muscles, the muscles in your arm do their work by contracting, becoming shorter and thicker. Muscle cells contract when they receive messages from the nervous system. Because muscle cells can only contract, not extend, skeletal muscles must work in pairs. While one muscle contracts, the other muscle in the pair relaxes to its original length. Muscle at Work First, the biceps muscle on the front of the upper arm contracts to bend the elbow, lifting the forearm and hand. As the biceps contracts, the triceps on the back of the upper arm relaxes and returns to its original length. Then, to straighten the elbow, the triceps muscle contracts. As the triceps contracts to extend the arm, the biceps relaxes and returns to its original length. Another example of muscles that work in pairs are those in your thigh that bend and straighten the knee joint. Use It or Lose It What happens when someone wears a cast for a broken arm? Skeletal muscles around the broken bone become smaller and weaker. The muscles weaken because they are not exercised. Exercised muscles are stronger and larger. Strong muscles can help other organs, too. For example, contracting muscles squeeze blood vessels. This action increases blood flow without needing more work from the heart. Strength and Flexibility Regular exercise is important for maintaining both muscular strength and flexibility. Exercise makes individual muscle cells grow in size. As a result, the whole muscle becomes thicker. The thicker a muscle is, the stronger the muscle is. When you stretch and warm up thoroughly before exercising, your muscles become more flexible. Stretching helps prepare your muscles for exercise or play. Resistance exercise requires muscles to overcome resistance (weight), this is a great way to strengthen skeletal muscles. Aerobic exercise is steady, moderately intense activity like walking, running, swimming laps, cycling , and skating. This can increase muscle strength to include the heart and it increases your endurance. Muscle Injuries However, despite taking proper precautions, muscles can become injured. A muscle strain, or pulled muscle, can occur when muscles are overworked or overstretched. Tendons can also be overstretched or partially torn., this is called tendonitis. (Rest is needed for it to heal) Muscle Injuries After a long period of exercise, a skeletal muscle can cramp. When a muscle cramps, the entire muscle contracts strongly and stays contracted. If you injure a muscle or tendon, it is important to follow medical instructions and to rest the injured area so it can heal. Disease and Disorders Muscular Dystrophy there are many types, but most cause progressive muscle weakness (it gets gradually worse), and many types can cause death. (Remember, the heart is a muscle, and muscles also control your breathing, swallowing, etc. If these muscles don't work properly...) Did you know!!!!! There are over 650 muscles, which make up about 40% of the body's weight. The diaphragm is a muscle which makes us breathe. When it contracts and pulls down, air fills your lungs. When it relaxes and lifts up, air is pushed out of your lungs. Pectorals Brachioradialis Deltoids Triceps Rectus Abdominus Biceps External Obliques Quadriceps Sartorius Gastrocnemius Picture from http://kidshealth.org/PageManager.jsp?lic=1&article_set=54399&cat_id=20607.
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