09 10 Muscle Contraction I and II

Smooth muscle structure and function activation

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Smooth Muscle Structure and Function Activation-Contraction Coupling Multiunit and Single-Unit Smooth Muscles
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Smooth Muscle: Structure and Function Function : Regulation of the dimension of hollow body organs (e.g. blood vessels, airways) at low energy cost Cell Morphology : Small and spindle-shaped, smooth appearance without striations Contractile Structure : Thin filament, thick filament, dense body, and dense plaques
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Smooth Muscle Cells are “Smooth” - Without Striation.
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Postulated Structure of Contractile Units in Smooth Muscle Cells
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Smooth Muscle Activation-Contraction Coupling Activation: Electrical and biochemical Regulation of Ca2+: A) Ca2+ influx through membrane calcium channels, and B) intracellular Ca2+ release from sarcoplasmic reticulum Ca2+-Dependent Regulation of Contraction: Myosin light chain phosphorylation Single-Unit Smooth Muscle – Synchonized activation via gap junctions (e.g. intestinal smooth muscle cells) Multi-Unit Smooth Muscle – Independent activation (e.g. smooth muscle cells in large arteries and large airways)
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Molecular Mechanism of Ca2+-Dependent Regulation of Smooth Muscle Contraction
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Comparison Between Ca2+-Dependent Regulatory Mechanisms in Smooth and Skeletal Muscle Skeletal Muscle Thin Filament- Based Regulation Smooth Muscle Thick Filament- Based Regulation
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Generation of Action Potentials in Smooth Muscle Membrane Potential Threshold Action Potentials Time Membrane Potential Pacemaker Potential Excitatory Stimulus Threshold Action Potentials Slow waves Spontaneous Generation of Action Potentials Stimulus-Induced Generation of Action Potentials
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Innervation of a Single-Unit Smooth Muscle Autonomic Nerve Fiber Varicosities (Containing Synaptic Vesicles) Gap Junctions
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