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).
Developmental Aspects of the Endocrine System. Endocrine glands derived from mesoderm produce steroid hormones; those derived from ectoderm or endoderm produce amines, peptides, or protein hormones. Environmental pollutants have been demonstrated to have effects on sex hormones, thyroid hormone, and glucocorticoids.evelopmental Aspects of the Endocrine System. Endocrine glands derived from mesoderm produce steroid hormones; those derived from ectoderm or endoderm produce amines, peptides, or protein hormones. Environmental pollutants have been demonstrated to have effects on sex hormones, thyroid hormone, and glucocorticoids.