Handout7TA - TA Clarissa Chan Section Wed 12-12:50p Coffee...

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TA: Clarissa Chan OH: Tues 10-11a Section: Wed 12-12:50p Mandeville Coffee Cart Handout #7 (through 2/18) o The longest duration (several seconds) of contraction exists in smooth muscle Can maintain tone over long periods of time without the use of a lot of ATP o Followed by Cardiac (~300-500msec) o The muscle with the shortest duration (10-100msec) of contraction is skeletal muscle Types of Smooth Muscle – Figure 12-25 o Single Unit : cells are connected by gap junctions Found in most hollow organs Efficient since not every cell requires innervations from an autonomic neuron Allows for peristaltic motions o Multi Unit : no gap junctions Each smooth muscle cell must be innervated by its own autonomic nerve Structure o No striations due to lack of sarcomeres o HAS actin and myosin o Myosins are different from the ones in skeletal muscle but have the same mechanism of action o No troponin or tropomyosin o Single nucleus Calcium Mechanism for Smooth Muscle – figure 12-28
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o Calcium enters the cytosol from intracellular or extracellular sources o Calcium binds to calmodulin ca2+-calmodulin activates Myosin Light Chain Protein Kinase (MLCK) MLCK uses ATP to phosphorylate myosin light chains allows myosin to bind actin power stroke o What causes relaxation?? Could remove calcium (pump it out of the cell or back into the SR) Ca2+ ATPases (SR) 3 Na+/ Ca2+ antiports (plasma membrane) o Phosphotase can remove phosphates from myosin light chains Cardiovascular Physiology o Systemic circulation is a high pressure, high resistance circulation dependent on the left ventricle o Pulmonary circulation is a low pressure, low resistance
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Handout7TA - TA Clarissa Chan Section Wed 12-12:50p Coffee...

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