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10 Cards in this Set

  • Front
  • Back
What is a sarcomere?
Contractile unit of a myocardial cell
What is the role of the intercalated disk?
Maintains cell to cell cohesion
What is the role of the gap junction?
Carries action potentials into the myocardial cell.
What is the role of the sarcoplasmic reticulum?
Stores and releases Ca+ for myocardial cell excitation-contraction coupling.
What occurs in excitation contraction coupling within the myocardium once the action potential enters the cell via the T tubules?
1. Ca+ enters the cell from the extracellular fluid, creating an inward Ca+ current.
2. Influx of Ca+ causes the SR to release its stores of Ca+ further increasing the intracellular Ca+
3. Ca+ binds to troponin C molecules, which removes the inhibition of actin and myosin binding by moving tropomysin out of the way.
4. Binding of actin and myosin allow the thick and thin filaments to slide past each other contracting the myocardial cell.
5. The SR reaccumulates the Ca+ which causes the myocardial cell to relax.
What influences the amount of Ca+ released by the SR during myocardial contraction?
Amount of Ca+ stored in the SR and ther size of the inward Ca+ current.
What is the magnitude of the contraction of a myocardial cell proportional to?
The intracellular Ca+.
Is reuptake of Ca+ by the SR during relaxation of the myocardium an active or passive process?
It is an active process mediated by Ca+ ATPase pump.
What is cardiac oxygen consumption related to?
It is directly related to the amount of tension developed in the cardiac muscle.
What are some factors that can increase cardiac O2 consumption?
1. Increased afterload
2. Increased contractility
3. Increased heart rate
4. Hypertrophy of the cardiac muscle.