1. 1.2 The Muscular System I.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.

2. 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

3. 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

4. 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

5. 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

6. 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.