cardiac muslce heart pump and contraction ch 9 Flashcards Preview

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Flashcards in cardiac muslce heart pump and contraction ch 9 Deck (46)
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minute work output

total energy converted in one minute.


work output of heart

spends energy on moving blood from low to high pressure. Also spends energy speeding blood to its velocity of ejection through the valves


the problem with having high systolic pressure

it pushes the actin and myosin filaments far apart and they stop working optimally


period of filing

volume increases as blood is pumped into ventricle


period of isovolumic contraction

all valves are closed so volume doesnt change but pressure does increase because the ventricles are contracting


period of ejection

systolic pressure rises even higher because of ventricular contraction . Volume is decreasing because the aortic valve is now open


period of isovolumic relaxation

aortic valve closes and ventricles fall back to starting point which is about 50 mmHg


How the heart gets energy

70-90 % is from metabolizing fatty acids. 10-30% from other nutrients like lactate and glucose


external work of the heart

oxygen consumption and chemical energy expended during contraction


potential energy of the heart

additional work that could be accomplished by contraction of the ventricle if the ventricle were completly emptied


what is the maximum efficency of the normal heart?

20-25 % . heart failure can go as low as 5-10%


Frank starling mechanism

The greater the heart muscle is stretched during filling, the greater the force of contraction it gives


sympathetic mechanism on heart

cause the heart to double its output


parasympathetic mechanism on heart

Vagus nerve, Can stop the heart for a couple seonds. Decrease pumping as much as 30% below normal


potassium ion effect

excess extracellular ions cause the heart to dilate and become flacid which slows the rate. Also block conduction system through AV node


Effect of calcium ions

spastic contractions!!!