In cardiac muscle, desmosomes hold the muscle fibers together. This helps the muscle withstand the constant contractions and relaxations of the heart's beating. Potassium is not released from the sarcoplasmic reticulum in cardiac muscle, calcium enters the cell from the sarcoplasmic reticulum, not intercalated discs, and an action potential spreads throughout the T tubules, not Z bands.

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In Cardiac Muscle

Question 40

Multiple Choice

In cardiac muscle:

A) potassium is released from the sarcoplasmic reticulum.
B) calcium enters the cell from storage chambers called intercalated discs.
C) an action potential spreads throughout the Z bands.
D) desmosomes hold the muscle fibers together.

Correct Answer: