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Flashcards in cardiac muscle mechanics Deck (45)
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31

what results in greater sarcomere stretching?

greater ventricle filling during diastole

32

what is the result of greater sarcomere stretching?

increased troponin C affinity for calcium-->more crossbridge formation per AP--> greater force of contraction during systole

33

how do inotropic agents increase force of contraction?

by increasing the amount of calcium release from the SR

34

in the heart what type of receptor does norepi bind to?

beta 1 adrenergic receptor

35

when NE binds to a beta 1 adrenergic receptor what 4 things increase?

cAMP
PKA
calcium
tension

36

after the administration of norepi how many beats does it usually take for the heart to reach its new steady state?

8 beats

37

how does norepi shorten twitch duration?

by accelerating the SR calcium uptake pump and calcium removal from the sarcoplasm

38

what does an increase in contractility do to twitch duration?

it decreases it

39

what is the result of PKA phosphorylating phospholamban?

increases SR Ca++ pump sensitivity which increases the rate of Ca+ uptake into the SR and therefore decreasing duration of muscle contraction

40

what are the two results of positive inotropic effects of beta adrenergic stimulation?

increased magnitude of contraction
decreased twitch duration

41

what is the positive chronotropic effect of beta adrenergic stimulation?

increased HR

42

what are the two ways to increase sensitivity of contractile apparatus to calcium?

1. use of certain drugs
2. increase initial fiber length (starling mechanism)

43

how would the curve be shifted in a tension vs calcium graph when NE is added?

the actual curve would not be shifted up but instead the muscle response would be shifted along the calcium tension curve

graph shown on page 369 of notes

44

would the curve be shifted in a tension vs length graph when NE is added? if so, which way?

YES the whole curve would be shifted up

graph shown on page 397 of notes

45

what is the effect on isotonic contraction of NE in the muscle?

isotonic contraction shortens twice the distance with the same load.
-the same contraction performed twice the work with NE