Lecture23-2009W - Fiber types in vertebrate skeletal muscle...

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1 Fiber types in vertebrate skeletal muscle checkbld tonic fibers : slow contraction, No AP e.g. eyeball muscle checkbld twitch (or phasic ) fibers: (a) slow oxidative (SO, type I) fibers barb2right contract slowly, fatigue slowly (b) fast oxidative (FO, type IIa) fibers barb2right rapid repetitive movements, fatigue barb2right e.g. flight muscles of migratory bird (c) fast glycolytic (FG, type IIb) fibers barb2right very rapid contraction, white, fatigue barb2right e.g. breast muscles of domestic fowl Mixtures of different muscle fibers Q) swimmer vs. cyclist? Energetics of muscle contraction checkbld ATP consumption : (a) Myosin ATPase - detatchment of myosin from actin - power stroke (b) Calcium pumps checkbld ATP regeneration during muscle activity (a) high-energy phosphatate (e.g. creatine phosphate)
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Unformatted text preview: (c) aerobic catabolism 2 Speed of muscle contraction/relaxation (1) myosin heavy chain isoforms : b the rate of ATP hydrolysis varies (2) Sequestration of Ca2+ by Ca2+ ATPase (3) Speed of contraction: FG > FO > SO Neuronal control of muscle contraction Vertebrates Invertebrates Motor unit c Vertebrates : (a) antagonistic pairs – flexor and extensor muscles (b) excitatory - ACh (c) increasing muscle tension b no gradation in a motor unit b High-frequency AP b activating more motor units b different types of muscle fibers c Arthropods: (a) all-or-none twitch + graded (multi-synaptic terminals) (b) multi-neuronal innervation (excitatory + inhibitory)...
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  • Spring '09
  • Tanda
  • muscle tension, different muscle fibers

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