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1Motor mechanisms II Review questionsBinding of ATP to myosin head causes:• a) actin filament to slide• b) Myosin head to detatch from actin filament• C) Myosin head to cockWhat will happen when ADP and Pidissociate from myosin head?• A) head will detatch from actin filament• B) head will retract and pull actin filament• C) head will bind ADP againCa++induces muscle contraction by:• A) Causing actin monomers to assemble into a filament• B) making ATP available to bind to myosin head• C) allowing myosin head to bind to actin filament2Muscle fiber types are the result of different types (isoforms) of myosin• Type I - slow fibers (aerobic)• Type II - fast fibers (anaerobic)– Type IIx - very fast– Type IIa - intermediate between II x and I– Types present in other vertebrates, not humans e.g., IIb in rats and other small mammals• Quadriceps muscle stained for ATPaseactivity. Dark = type II fast; light = type I slow.• Type I and II stained for mitochondria. Type I has dense mitochondria since it is aerobic• Type I slow twitch– Slow contraction time (100 msec)– Myoglobin (red)– Continuous use– More capillaries– Small size– Low glycogen– High fat– More mitochondria• Type II fast twitch– Fast contraction (50 msec)– No myoglobin(white)– Brief use– Few capillaries– Larger size– High glycogen– Low fat– Few mitochondria3Characteristics of other muscle types:• Cardiac muscle - found only in the heart, striated, gap junctions allow direct electrical signaling between cells• Smooth muscle - involuntary muscle, meshwork of actin and myosin, can contract more (greater shortening), but with less tension.Muscle cell types schematic:1) skeletal2) cardiac3) smooth123Skeletal muscleCardiacmusclehttp://www.youtube.com/watch?v=Cdl8Awn_lDY&feature=relatedhttp://www.youtube.com/watch?v=b1WD564sjWw&feature=relatedSmooth


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WSU BIOLOGY 103 - Motor Mechanisms II

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