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Unformatted text preview: Lecture 6 – Smooth Muscle non voluntary I. Myofiber Anatomy 1. Size diameter 2 – 5 μ length 50 – 100 μ (1 nucleus) 2. Myofilaments Not striated Random pattern of actin and myosin Less crowding Longer actin/myosin filaments shorten 50-70% of original length II. AP’s – a lot of smooth muscle cells don’t fire AP’s 1. Depolarization – based on ions floating across membrane L (long acting) – type Ca++ channels open up Ca++ influx Ca++ channels stay open longer than Na+ channel 2. Repolarization based on opening up of K+ channels 3. “Slow wave depolarization” at rest (drifts towards threshold on its own) pacemaker Beating frequency muscle can develop on its own Zaps on its own 4. Spread of depolarization – no T-tubules Gap junctions electrical connections that connect cells Act as “syncition” (fire together) III. Contraction Long duration sec-min multiple AP’s, almost like summation twitches Slow myosin-actin interaction...
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- Winter '08