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26 Cards in this Set
- Front
- Back
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Cardiomyocytes are striated muscles.
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True
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AP are initiated by neural activity.
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False
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Nerves affect heart rate and strength of contraction.
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True
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What are intercalated disks?
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-Electrical connections(gap junctions)
-Mechanical connections(desmosomes) -Functional syncytium |
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Myocardial cells are branched and have a single nucleus.
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True
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AP plateau is due
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to Extended Ca entry
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What is special about cardiomyocyte metabolism?
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Aerobic metabolism with:
-no rest periods -no oxygen debts allowed -many mitochondria |
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AP open Ca channels on sarcolemma
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True
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AP travels down T tubules and cause Ca release from SR.
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True-Ca induced Ca release
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Ca ions bind to troponin to initiate contraction.
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True
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Relaxation occurs when Ca unbinds from troponin.
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True
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What is a sarcomere and what consitutes it?
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A molecular motor.
-Thick filaments(myosin) -Thin filaments(actin) -Overlap and energy dependent sliding. |
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Myosin cant interact with actin as
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Troponin gets in the way.(regulatory complex of tropomyosin and troponin prevents interaction between actin and myosin)
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What moves tropomyosin away?
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Ca + troponin.
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What happens during relaxation?
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Active pumps return Ca to SR and extracellular fluid.
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Ca also exhanged for extracellular Na+.
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True(then pumped out via Na/K ATPase)
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What determines overlap of thick and thin filaments?
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Cell length.
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What is the length of relaxed cells determined by?
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Volume of blood in the ventricle.
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What does degree of overlap depend on?
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End diastolic volume.----> tension produced.
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What happens at a certain length?
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Overlap between thick and thin filaments is optimal and (for a given rise in Ca)will result in maximal tension.
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Normal cell length is less than optimal.
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True(allowing room for increased tension)
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Symp and parasymp. NS are both inotropic and chronotropic
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True
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How do you call factors that affect contractility?
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Inotropic
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Inotropic factors often affect cytoplasmic Ca levels.
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True
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Hormones such as adrenaline will increase tension.
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True
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Digoxin increase contractility by what mechanism?
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Inhibitor of Na/K ATPase-cardiomyocyte not pumping out Na+,thus amount of Na+ entering decreases with less Ca2+ out.
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