The word 惊心动魄 is formed by combining two parallel verb-object phrases: 惊心 (shocking the heart) and 动魄 (moving the soul). Here, 惊 (to shock) modifies 心 (heart), and 动 (to move) modifies 魄 (soul), with each pair intensifying the other to collectively convey a meaning of profound emotional agitation or thrilling terror.