Anatomy - KIN 216 Chapter 10 Slides adapted from Dr...

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KIN 216 Chapter 10 Slides adapted from Dr Pfeiffer
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Muscle Muscle composition and number Compose about 40% of total body weight Almost 600 muscles (about 3 muscles for every bone) Composition Mostly H2O (>2/3, ~70%) Most of the rest is protein (especially actin and myosin) Small amount of CHO (stored as glycogen) Small amount of lipid (stored) Myology = study of muscles Myalgia = pain in muscle Myokymia = twitching of muscle segments
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Muscle Characteristics Excitability (or Irritability) Muscle tissue contracts in response to nervous (electrical) stimuli (electrical current is ion movement) Contractility Muscle tissue responds to electrical stimuli by contracting (shortening) NOTE: muscles only pull, they don’t push, so opposing muscle actions are caused by shortening of antagonists EX: elbow flexion (agonist = biceps, antagonist = triceps), while elbow extension (agonist = triceps, antagonist = biceps) Extensibility Once muscle fibers relax they can be stretched beyond their resting length by contraction of opposing muscle Elasticity Muscle fibers recoil to original length after stretching
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Muscle Functions Movement Move the body (and/or parts of the body) Thermogenesis Heat production Are in a continuous state of fiber activity Posture/support Maintain posture, stabilize joints, support viscera Many times you don’t even notice that postural muscles are working
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Muscle Tissue Types Skeletal muscle Striated, voluntary Cells are called fibers Cardiac muscle Striated, involuntary Smooth muscle NO striations, involuntary Cells are called fibers Contraction of muscle depends upon myofilaments (located in cytoplasm) Plasmalemma = sarcolemma Cytoplasm = sarcoplasm
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Skeletal Muscle Connective Tissue : Endomysium Surrounds individual muscle cells (aka muscle fibers) Binds adjacent fibers together and supports capillaries and nerve endings that serve the muscle fibers Perimysium Binds group of muscle cells Group of muscle cells = fascicle (smallest unit that can be seen with naked eye) Also supports blood vessels and nerve fibers Epimysium Binds fascicles together (dense irregular CT) – surrounds entire muscle Is continuous with tendon (tendon arises from it) All 3 layers are continuous with the tendons of mm Fascia : fibrous CT that covers muscle and attaches it to skin
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Nerves and Blood Vessels Generally, each skeletal muscle is supplied by one nerve, one artery, and one or more veins ***Each muscle fiber is contracted by one nerve ending – Contact point is neuromuscular junction (aka motor endplate) Motor unit = one motor neuron and all the muscle fibers
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Anatomy - KIN 216 Chapter 10 Slides adapted from Dr...

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