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Content: Force is controlled by Ca2+ however cardiac muscle is less dependent on the release of Ca2+ from the SR and the mechanism is different (calcium induced calcium release)
3. Cardiac muscle cells depend primarily on oxidative phosphorylation to generate ATP. They are resistant to fatigue and depend on a continuous supply of oxygen
4. Cardiac muscle cells are much shorter than skeletal muscle fibers and are branched. 5. Cardiac muscle cells are joined together by intercalated discs (desmosomes and gap junctions)
Define the mechanical and functional role of the intercalated disc
Desmosomes mechanically adhere cells together
Gap junctions electrically connect cells and allow action potentials of one cell to spread to another. This allows the heart to contract as a unit. Compare and contrast the excitation-contraction coupling in cardiac and skeletal muscle
The organization of the membrane system involved in excitation-contraction coupling is similar to that in skeletal muscle. A few diffferences include sparser sarcoplasmic reticulum, t-tubules positioned near Z lines instead of A-I band junctions, t-tubules are larger in diameter, SR makes junctions with t-tubules, dyads in cardiac muscle vs triads in skeletal muscle. Explain the mechanisms of Ca2+ entry and extrusion from cardiac muscle cells
Action potential initiated by pacemaker cells propagates to the sarcolemma and spreads into the T-tubular membrane.