Flashcards in cardiac muscle mechanics Deck (45)
what results in greater sarcomere stretching?
greater ventricle filling during diastole
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
how do inotropic agents increase force of contraction?
by increasing the amount of calcium release from the SR
in the heart what type of receptor does norepi bind to?
beta 1 adrenergic receptor
when NE binds to a beta 1 adrenergic receptor what 4 things increase?
after the administration of norepi how many beats does it usually take for the heart to reach its new steady state?
how does norepi shorten twitch duration?
by accelerating the SR calcium uptake pump and calcium removal from the sarcoplasm
what does an increase in contractility do to twitch duration?
it decreases it
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
what are the two results of positive inotropic effects of beta adrenergic stimulation?
increased magnitude of contraction
decreased twitch duration
what is the positive chronotropic effect of beta adrenergic stimulation?
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)
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
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