e.g, the plasma (increased/decreased) concentration of a factor X triggers the secretion of the hormone. In turn, the hormone affects the secretion of the factor X in target cells and controls its plasma level (e.g., parathyroid hormone, Fig.7-10). - More complex pathway: The hormone secretion and/or synthesis is under the control of multiple distinct stimuli (e.g., insulin, Fig 7-9). C.2. Pathway of neurohormonesNeurohormones are synthesized and secreted by neurons: - posterior pituitary hormones (Figs. 7-11, 7-12, 7-13), - hormones of the hypothalamus that control the release of hormones by the anterior pituitary (Figs. 7-11, 7-13, 7-14, 7-15), - catecholamines made by the adrenal medulla. C.3. Pathway of hormones under trophic hormone control- tropic(Greek, trophikos, = nourishment) hormone. •Definition of trophic hormone: Any hormone that controls the secretion of another hormone is trophic •e.g., hormones of the anterior pituitary (Figs. 7-13 7-14). C.4. Hormone interactions- Some hormones have a permissive actionon the effects of other hormones.
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