smooth muscle
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Created by:
shouldabeenadentist on February 20, 2012
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10 terms
Terms | Definitions |
|---|---|
 structure of smooth muscle | absence of sarcomeres - filaments arranged in network and connected by dense bodies to cytoskeleton |
| types of smooth muscle | tonic - continuous active tone (vascular) with constant stimulus, can twitch with short stimulus phasic - twitch-like behavior (ureter or vas deferens) with stimulus, could summate twitches |
| innervation of smooth muscle | multi-unit - each fiber receives input, finer control (vascular, airway, ciliary muscles) unitary - only a few cells receive input, allows several cells to act as one, prominent gap junctions (GI, bladder, some vessels) |
| contraction process of smooth muscle | Ca enters cell, activates calmodulin calmodulin phosphorylates MLCK MLCK activates myosin ATPase (on regulatory light chain) allows actin-myosin interaction smooth muscle has 10% ATPase activity of skeletal no troponin |
| skeletal vs smooth muscle contraction | skeletal: disinhibition of TnC/TnI smooth: activation of ATPase light chain |
| smooth muscle contraction biophysics | time course is slower phasic contraction correlates with intracellular Na tonic contraction occurs with "latch-bridge" cycling reduced ATP turnover can modulate force (not all or nothing) |
| smooth muscle action potential | no fast Na channels VG Ca channels open (spike) Ca influx causes Ca-dependent K channels to open (slow hyperpolarization) Ca channels close, [Ca] decreases, Ca-denpendent K channels close |
| types of smooth muscle stimuli | pharmaco-mechanical coupling 1) VG Ca channel 2) agonist binding to Gq protein (IP3 release of intracellular Ca stores in SR) (NE, ADH, AngII, ACh) |
| control of intracellular Ca | Na/Ca exchanger and Ca pump SERCA on SR SR binds Ca on proteins (calsequestrin & calreticulin) SERCA regulated by phospholamban (some cells have, some don't) |
| endothelial modulated relaxation | vasodilating factors (ACh, histamine, bradykinin) induce NOS NO stimulates GC cGMP activates PKG PKG inhibits Ca accumulation and stimluates MP activity |
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