Which statement about cardiac muscle is FALSE?
◦ Intercalated disks contain both desmosomes for firm attachment and gap junctions to allow communication.
◦ Cardiac muscle cells must obey the all-or-none law of contraction.
◦ Calcium-induced calcium release is when extracellular Ca2+ stimulates release of Ca2+ from the sarcoplasmic reticulum.
◦ Cardiac muscle cells use Ca2+ ions released from the sarcoplasmic reticulum.
◦ The energy demand of cardiac muscle cells is high because they have many mitochondria.