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The muscular system is a complex network of over 600 muscles that facilitates movement in the human body. Muscles can be classified into three types: skeletal, cardiac, and smooth, each serving distinct functions. Skeletal muscles are voluntary and enable rapid movement, while cardiac and smooth muscles operate involuntarily. Muscle movement is powered by energy and operates through levers in the body. Muscles work in pairs, always pulling rather than pushing, and can strengthen through exercise or weaken with inactivity. Understanding these principles is key to improving physical health.
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1.2 The Muscular System Movement of the Human Body A. Muscle: organ that contracts and relaxes to provide movement. 1. Movement requires energy 2. >600 muscles in the human body! B. Muscle Control 1. Voluntary muscles: you consciously control them. 2. Involuntary muscles: you DO NOT consciously control them.
II. Your Body’s Simple Machines – Levers A. Three Types of Levers 1. First Class a. Fulcrum between input and output b. Neck muscles to tilt head 2. Second Class a. Output force between input and fulcrum b. Calf muscles point toes 3. Third Class a. Input between fulcrum and output b. Biceps flex arm
III. Classification of Muscle Tissue • A. Skeletal Muscles • 1. Move bones • 2. Attached to bones by tendons • 3. Striated – striped • 4. Voluntary • 5. Move quickly • B. Cardiac Muscles • 1. Found in the heart
2. Also striated 3. Contract about 70 times/minute all day, every day 4. Involuntary 5. Move quickly C. Smooth muscles 1. Found in internal organs 2. Not striated 3. Move slowly 4. Involuntary
IV. Working Muscles A. Muscles work in pairs B. Always pull, never push C. Changes in Muscles 1. Exercising muscles get stronger 2. Increase in muscle size occurs b/c muscle cells get bigger 3. Inactivity causes muscles to get weak and shrink
D. How muscles move 1. Chemical energy and oxygen are “fuel” 2. Release energy in form of movement and heat 3. When muscles use a lot of oxygen and chemical energy, they get fatigued and feel heavy.