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Human Body Systems Lesson 21 Terms and Definitions Q: Why do muscles get tired? Muscle Fatigue Muscle Fatigue – the reduced ability of a muscle to contract. http://run4change.files.wordpress.com/2009/04/exhuasted-runner1.jpg http://shakeout.files.wordpress.com/2008/11/tired_runner.jpg Muscle Fatigue Why? 1. Muscles need energy (ATP) from cellular respiration 2. Fatigue happens when… ATP produced cannot keep up with ATP needed by muscles Light exercise • Aerobic respiration can produce most of the ATP energy needed for light exercise. • When there’s not enough Oxygen present, Anaerobic Respiration occurs. – Lactic acid builds up, causing fatigue – Lactic acid is washed out of muscles within 30 minutes after exercise. Muscle Fatigue • Avoid fatigue by training and practicing. Slow Twitch Muscles • Muscle fibers are slow to contract • Endurance • More mitochondria, more myoglobin – Myoglobin – reddish protein that stores O2 and gives muscle fibers color. • Found in Athletes that sustain a moderate level of activity for extended periods of time. Ex. Cyclist, marathon runners, etc. http://z.about.com/d/bicycling/1/0/6/1/-/-/71398008.jpg Fast Twitch Muscles • Fibers contract rapidly • Fewer Mitochondria, Less myoglobin • Found in: athletes that do rapid activites. Ex. Weight lifters, sprinters. http://www.baspeed.com/userfiles/sports/lianalambert%20weightlifter.jpg Fast Slow Chickens/Turkey White/Light meat Don’t fly Fast Twitch Fibers Less endurance Less myoglobin Ducks Dark meat Fly A LOT! Slow Twitch fibers Lots of endurance More myoglobin A CRAMP!!! AAAAHHHHH A MUSCLE CRAMP!!! A cramp • Cramp – a sustained muscle contraction of a muscle group. – WHEN: during/following exercise/NO apparent reason. – CAUSES: could be low blood sugar, electrolyte depletion (sodium/calcium), and dehydration Q: How do muscles contract? Muscle Contractions 1. Nerve sends a signal to muscle 2. Actual Contraction (2/3’s its size). 3. Relaxation Contraction takes approx. 10-100 milliseconds!!