6. smooth muscle

6. smooth muscle - 6. Smooth Muscle I. Visceral (single...

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6. Smooth Muscle I. Visceral (single unit) vs skeletal muscle a. Skeletal i. Fiber size 1. Diameter 10-80 microns 2. length of muscle ii. Structure 1. Striated, rigid structure 2. Shortens 25-30% with contraction 3. Actin: myosin ratio 2-4:1 iii. MAP 1. Fast spiky, neurogenic iv. MAP spread 1. Along sarcolemma, down t-tubules 2. No electrical connection between cells v. Ca++ delivery 1. Sarcoplasmic reticulum well developed- Ca++ dumped/pumped quickly 2. Mechanically fast- hormone independent vi. Contraction 1. Ca++ from SR binds to Troponin-C releases tropomyosin 2. Fast actin/myosin interaction 3. High ATPase vii. Duration of contractions 1. Fast: 10-100 ms b. Smooth muscle/ visceral single unit i. Fiber size 1. Diameter- 2-5 microns 2. Length 50-100 microns ii. Structure 1. Not striated 2. No sarcomere/ bands 3. Shorten 50-70% with contraction 4. Actin: myosin ratio 10-15:1 iii. MAP 1. Depolarization- L-type Ca++ channels long acting contraction- Ca++ influx 2. Repolarization- increase of permeability of K+
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6. smooth muscle - 6. Smooth Muscle I. Visceral (single...

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