1. Muscular System

2. Three Types Skeletal or striated – attached to bones, allows motion, voluntary control Smooth - work internal systems, involuntary i. e. digestive and circulatory Cardiac – heart muscle, involuntary

3. Skeletal Muscle Works in pairs, one bends joint the other extends or straightens joint For full motion opposite muscle must relax while one flexes or contracts Muscle cells contract in response to nerves signals Contracting unit of a muscle – myofibril Under voluntary control

4. Myofibril Two types of proteins in contracting unit: myosin and actin Proteins slide over each other and overlap when contracted

5. Skeletal Muscle cont. Two proteins (myosin and actin) give muscles a striped effect under a microscope – striated means banded or striped Two types of cells: –Red muscle cells – work longer –White muscle cells – work stronger

6. Skeletal Muscle cont. Humans have muscles with both types of cells Exercise increases the size of your cells Skeletal muscles have multiple nuclei

7. Cardiac Muscle Found in the heart Average adult heart rate – 60 – 100 bpm Less striped than skeletal muscle Have only one nucleus per cell involuntary

8. Smooth Muscle Short non-striped muscle cells One nucleus per cell Found in cell walls of veins, arteries, digestive system, respiratory system etc. involuntary

9. Healthy Muscles Diet needs to include enough protein Enough energy to fuel muscles Strongest at about 25 years old

10. Identifying Injuries X-Rays – form of energy that travels in waves Shows bones, good for detecting fractures Goes through soft tissue but not bones Bones show up as white areas Need to be careful of exposure to X-Rays

11. MRI Magnetic Resonance Imaging Clear images of both bones and soft tissue Magnetic energy causes atoms in your body to vibrate (resonate). Computer analyzes vibration pattern to form image No evidence it cause any harm Fairly expensive

12. Muscles to Know