hedgehog cactus: cactus of the genus Echinocactus having stout sharp spines
echinocactus: any cactus of the genus Echinocactus; strongly ribbed and very spiny; southwestern United States to Brazil
cardiac cycle: the complete cycle of events in the heart from the beginning of one heart beat to the beginning of the next; an electrical impulse conducted through the heart muscle that constricts the atria which is followed by constriction of the ventricles