Neuroendocrinology its product?" and "how is information encoded in electrical activity?"[It appears that this is a primary source observation.] The pituitary gland is divided into two sections: the anterior pituitary and the posterior pituitary. The hypothalamus controls the anterior pituitary's hormone secretion by sending trophic hormones down the hypothalamohypophysial portal system. For example, thyrotropin-releasing hormone stimulates the secretion of thyroid-stimulating hormone by the anterior pituitary. The posterior pituitary is innervated by the hypothalamus; the hormones oxytocin and vasopressin are synthesized by neuroendocrine cells in the hypothalamus and stored at the nerves' ends in the posterior pituitary. They are secreted directly into
Pituitary gland often not clearly marked. In elasmobranchs there is an additional, "ventral lobe" beneath the anterior pituitary proper. The arrangement in lampreys, which are among the most primitive of all fish, may indicate how the pituitary originally evolved in ancestral vertebrates. Here, the posterior pituitary is a simple flat sheet of tissue at the base of the brain, and there is no pituitary stalk. Rathke's pouch remains open to the outside, close to the nasal openings. Closely associated with the pouch are three distinct clusters of glandular tissue, corresponding to the intermediate lobe, and the rostral and proximal portions of the