Animal Hormones

Some endocrine cells aggregate into secretory organs

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Unformatted text preview: Cholecystokinin, Gastric inhibitory peptide). • Some endocrine cells aggregate into secretory organs called endocrine glands. • In vertebrates, nine major endocrine glands make up the endocrine system. 27 28 Figure 42.2 The Endocrine System of Humans 41 The pituitary gland • The pituitary gland of mammals is a link between the nervous system and many endocrine glands and plays a crucial role in the endocrine system. • The pituitary gland sits in a depression at the bottom of the skull and is attached to the hypothalamus. • The pituitary is made of two parts: anterior and posterior. 29 30 Figure 42.5 The Posterior Pituitary Releases Neurohormones Figure 42.7 Hormones from the Hypothalamus Control the Anterior Pituitary • The anterior pituitary is controlled by neurohormones from the hypothalamus • The posterior pituitary releases two hormones: antidiuretic hormone and oxytocin. • They are made by neurons in the hypothalamus, are called neurohormones, and are packaged in vesicles. 31 32 41 The hormones of the anterior pituitary • The anterior pituitary releases four tropic hormones, which control activities of other endocrine glands. 41 Growth hormone • Growth hormone (GH): • 191 amino acids • acts on many tissues to promote growth. ! thyrotropin, adrenocorticotropin, luteinizing hormone, and follicle-stimulating hormone. ! They are peptide and protein hormones; each is produced by a different type of pituitary cell. • The anterior pituitary also releases other polypeptide hormones that are not tropic hormones. ! growth hormone, prolactin, melanocyte-stimulating hormone, endorphins, and enkephalins. 33 34 Figure 42.6 Effects of Excess Growth Hormone 41 Growth hormone signaling 35 • Gigantism is the result of overproduction of GH in children. 36 Figure 42.2 The Endocrine System of Humans • GH deficiency in children causes pituitary dwarfism • When treated with GH, a deficient child will begin to grow faster within months. • From the late 1950s, pituitary dwarfism was treated with GH extracted from pituitaries from human cadavers: years’ supply required 50 pituitaries...
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