1. Macro Muscles Let’s Start with a Video…

3. Motor Unit Smaller # fibers – more precise movement Larger # fibers – more powerful contraction

4. TWITCH Quick jerk (1/10 th sec) due to brief threshold stimulus CONTRACTIONS Muscle contracts more forcefully after it has contracted a few times Warm-up before exercise UNFUSED TETANUS Very short periods of relaxation between peaks of tension FUSED TETANUS Smooth, sustained contractions SR releasing Ca+2 Ca+2 bind to troponin; Cross-bridging

5. Length-tension Relationship Sarcomere compressed Muscle can’t develop tension Optimal length Strongest max contraction possible Overstretched Muscle can’t develop tension due to filaments too far apart

6. ATP Sources- Energy for muscles Aerobic Respiration – Requires O 2 – Produces max amount of energy available from each glucose molecule Anaerobic Respiration – Occurs when lack of O 2 – Forms lactic acid During exercise Muscles “burn” – O 2 debt Heavy breathing during exercise in order to process lactic acid

7. Muscle Fatigue Muscles loses ability to contract due to lack of ATP Lactic acid build up

8. Myopathies Myalgia - muscle pain due to overstretching/tearing of muscle fibers Strain – caused by overexertion/trauma and can lead to muscle tear Myositis - any muscle inflammation Fibromyositis - tendon inflammation along with myositis Cramps – Painful muscle spasms Last few seconds to few hours Caused by injury or overuse – Dehydration – Low K+ or Ca+2

9. Myopathies Contusion – Muscle bruise, local internal bleeding and inflammation Poilio – Viral infection of nerves controlling skeletal movement – Causes partial or full paralysis and death – Vaccine created in US in 1950s, but not everywhere Muscular Dystrophy – Genetic disease caused by muscle atrophy – Some forms are fatal

10. Myopathies Hernias – “protrusion” – Reducible – can manipulate protruding organ back into abdominal cavity – Strangulated – blood flow to organ is stopped; obstruction, gangrene, pain. Vomiting, emergency surgery – Types Inguinal – hernia extends into inguinal canal into scrotum or labia; affects more males Femoral – affects more women below groin area due to pregnancy