Hence, an arrow which bends less is said to have more spine. In order to strike consistently, a group of arrows must be similarly spined. Center-shot bows, in which the arrow passes through the central vertical axis of the bow riser, may obtain consistent results from arrows with a wide range of spines.
Definition of MELATONIN. : a vertebrate hormone that is derived from serotonin, is secreted by the pineal gland especially in response to darkness, and has been linked to the regulation of circadian rhythms.See melatonin defined for kids.ADVERTISEMENT. Greek melas black + -tonin (as in serotonin).efinition of MELATONIN. : a vertebrate hormone that is derived from serotonin, is secreted by the pineal gland especially in response to darkness, and has been linked to the regulation of circadian rhythms. See melatonin defined for kids. ADVERTISEMENT. Greek melas black + -tonin (as in serotonin).
A hormone, C 13 H 16 N 2 O 2, derived from serotonin and produced by the pineal gland. It stimulates color change in the epidermis of amphibians and reptiles and plays a role in the function of circadian rhythms and estrous cycles in mammals.oun. 1. melatonin-hormone secreted by the pineal gland. endocrine, hormone, internal secretion-the secretion of an endocrine gland that is transmitted by the blood to the tissue on which it has a specific effect. Translations. n melatonina.