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26 Cards in this Set

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