Final answer:
The assertion that calcium ions are released from the sarcoplasmic reticulum due to direct interaction with voltage-gated Ca2+ channels in cardiac muscle is false.
Step-by-step explanation:
The statement that in cardiac muscle, calcium ions are released from the sarcoplasmic reticulum due to direct interaction with the voltage-gated Ca2+ channels is false. In cardiac muscle cells, calcium ions initiate contraction by entering the cell through voltage-gated calcium channels during the plateau phase of the action potential. This influx of calcium then stimulates the release of more calcium from the sarcoplasmic reticulum (SR), a process known as calcium-induced calcium release (CICR). A small portion of the calcium needed for contraction comes from this entry, while the majority is released from storage within the SR.
Instead, calcium influx through voltage-gated calcium channels triggers further calcium release from the sarcoplasmic reticulum, a process essential for cardiac muscle contraction.