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Muscular System. Movement of the Human Body. Muscle: an organ that can relax, contract, and provide the force to move your body parts You have more than 600 muscles in your body Some of them are always moving. Voluntary and Involuntary Muscles.
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Movement of the Human Body • Muscle: an organ that can relax, contract, and provide the force to move your body parts • You have more than 600 muscles in your body • Some of them are always moving
Voluntary and Involuntary Muscles • Voluntary muscles: muscles that you are able to control • In your face, arms, and legs • You can choose to move them or not to move them • Involuntary muscles: muscles that you are not able to consciously control • Pump blood through your blood vessels • Move food through your digestive system
Classification of Muscle Tissue • There are three types of muscles • Skeletal muscle: voluntary muscles that move bones • Are striated and are the most common muscle type in your body • Are attached to bones by thick bands of tissue called tendons • Cardiac muscle: involuntary muscle that is only found in the heart • Contracts about 70 times per minute • Is striated • Smooth muscle: involuntary muscles that control movement in your intestines, bladder, blood vessels, and other internal organs • Not striated
Working Muscles • You are able to move because pairs of skeletal muscles work together • When one muscle contracts, the other muscle relaxes • Muscles ALWAYS pull; they NEVER push • Remember: Yo-Yo • When the muscles on the back of your upper leg contract, they shorten and pull your lower leg back up • When you straighten your leg, the back muscles lengthen and relax, and the muscles on the front of your leg contract
Changing Muscles • Skeletal muscles that do a lot of work become stronger and larger • Some of this change in muscle size is because of an increase in the number of muscle cells • Most of the change is because individual muscle cells become larger • Muscles that are not exercised become smaller and weaker
How Do Muscles Move? • Your muscles need energy to contract and relax • Your blood carries energy-rich molecules to your muscle cells where the chemical energy stored in these molecules is released • As the muscle contracts, this released energy changes to mechanical energy (movement) and thermal energy (heat) • Once the supply of energy-rich molecules in the muscle is used up, the muscle becomes tired and needs to rest • While your muscle rests, your blood supplies more energy-rich molecules to your muscle cells