Muscular System

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