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Clarification 1. Eccentric contraction • think: Bicep brachii • buffers slow descent of heavy object • still contracting, but elongating © 2012 Pearson Education, Inc. In the news… © 2012 Pearson Education, Inc. New human-body part! Types of Muscles Fibers and Endurance • Two Speeds of Skeletal Muscle Fibers 1. Fast fibers 2. Slow fibers • Two ATP-forming types of Skeletal Muscle Fibers 1. Oxidative 2. Glycolytic • Mix them up! © 2012 Pearson Education, Inc. Types of Muscles Fibers and Endurance Slow Fast © 2012 Pearson Education, Inc. Oxidative Glycolytic Slow Oxid Slow Glyco Fast Oxid Fast Glyco Types of Muscles Fibers and Endurance Think: High Endurance • Slow Oxidative Fibers • slow to contract • Contains lots of myoglobin © 2012 Pearson Education, Inc. Myoglobin Types of Muscles Fibers and Endurance • Fast Glycolytic Fibers • Contract very quickly • strong contractions, fatigue quickly • Lots of glycogen reserves • No Oxygen • Large diameter • Few mitochondria © 2012 Pearson Education, Inc. © 2012 Pearson Education, Inc. Clarification 1. Eccentric contraction • think: Bicep brachii • buffers slow descent of heavy object • still contracting, but elongating © 2012 Pearson Education, Inc. In the news… © 2012 Pearson Education, Inc. New human-body part! © 2012 Pearson Education, Inc. Dark Meat vs. White Meat Fast glycolytic Slow Oxidative © 2012 Pearson Education, Inc. Think locomotion! Types of Muscles Fibers and Endurance • Fast Oxidative Fibers • Less common • Characteristics like SO and FG • O2 dependent like SO • Quick like FG • Most muscles mix SO, FG, FO • But each motor unit is the same type of fiber • Exercise can turn FG à FO © 2012 Pearson Education, Inc. Types of Muscles Fibers and Endurance • How does exercise affect muscle? © 2012 Pearson Education, Inc. Muscle Atrophy But what about types of exercise? Exercise Adaptations • Aerobic Exercises • é #capillaries • é #mitochondria • é Myoglobin synthesis • Since AERObic…Δs most pronounced in SO • Result: éresistance, endurance, less fatigue • But no, big mass gain © 2012 Pearson Education, Inc. Exercise Adaptations • High intensity resistance exerciseà hypertrophy Result of: • é FG cell size • splitting of cells • addition of satellites • FO à FG • Hypertrophy complications © 2012 Pearson Education, Inc. Smooth Muscle © 2012 Pearson Education, Inc. Smooth Muscle • Spindle shaped • 1/10th Skel. Musc. cell width • 1/1000s Skel. Musc. cell length • Some endomysium (No Peri- or Epi-) • Organized into sheets • Typically two • outside [longi] • inside [circ] © 2012 Pearson Education, Inc. Innervation of Smooth Muscle • No NMJ • Instead Varicosities • bulbous swellings of nerve fibers • release neurotransmitter into diffuse junctions © 2012 Pearson Education, Inc. Varicosities © 2012 Pearson Education, Inc. Innervation of Smooth Muscle • Reduced SR • No T-tubules • instead Caveolae (Latin “Little Caves”) © 2012 Pearson Education, Inc. Caveolae Caveolae sequester Ca2+ from ECF Striations on cell? No No sarcomeres © 2012 Pearson Education, Inc. Myofilaments in Smooth Muscle • Three main differences in microanatomy 1. No troponin • Instead: protein calmodulin 2. Myofilaments spirally arranged • contract in corkscrew manner © 2012 Pearson Education, Inc. Nucleus Contracted smooth muscle fiber © 2013 Pearson Education, Inc. Inc. © 2012 Pearson Education, Dense bodies Intermediate filament Dense bodies 3. Intermediate Filaments – Dense bodies network • Dense bodies • anchor intermediate filaments to sarcolemma • Cable-like structure • harnesses contraction • syncs all cells to each other © 2012 Pearson Education, Inc.
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