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13609 Smooth Muscle Outline

13609 Smooth Muscle Outline - hormones and"local...

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MUSCLE Smooth Muscle Tissue and cellular structure: mononucleated cells, often with gap junctions single unit and multiunit smooth muscle actin+myosin and "sarcomeres" (dense bodies and membrane attachments) regulatory: calmodulin and myosin light chain (MLC) kinase and MLC phosphatase sarcoplasmic reticulum (SR) less well organized, has SERCA and both IP3R and RyR Contraction actin+myosin, slow rate of contraction "latch state" with higher efficiency (i.e., increased contraction/ATP) Electrical activity slow waves and action potentials autonomic nerves and varicosities neurotransmitters can be both excitatory and inhibitory norepinephrine --> alpha adrenergic receptors, contraction of vascular smooth muscle norepinephrine --> beta2 receptors, relax respiratory smooth muscle
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Unformatted text preview: hormones and "local factors" (e.g., nitric oxide, NO, and histamine) affect electrical activity Triggering contraction: Ca entry to cytosol Ca enters through plasma membrane channels and ER/SR Ca channels (RyR and IP 3 R) Plasma membrane channels depolarization: action potentials, but AP's not required hormones and local factors may increase Ca entry without action potentials "store-operated" channels RyR in ER/SR Ca-induced Ca release (CICR) IP 3 R in ER/SR hormones (epinephrine) and local factors (e.g., NO, histamine, ATP, adenosine) CICR Summary: contract and relax Regulation autonomic nerves hormones local factors cell stretch (single unit)...
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