PHGY 210 Lecture Notes - Lecture 3: Corticotropin-Releasing Hormone, Pituitary Stalk, Posterior Pituitary
3 Feb 2018
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Document Summary
Hormone secretion is precisely regulated by feedback mechanism. An excess of hormone, or excess hormonal activity, leads to a decrease of hormone secretion. Conversely, deficiency of hormone leads to an increase in hormone secretion. E. g. , ca++ acts in a negative feedback loop to regulated plasma calcium level. Located at the base of the brain, with 2 distinctly different tissues: Adenohypophysis (aka anterior pituitary, or pars distalis) endocrine tissue. Neurohypophysis (aka posterior pituitary, or pars nervosa) neural tissue (posterior pituitary is an extension of the hypothalamus) Prolactin release inhibiting hormone (pih) is also known as dopamine (neural hormone), so can act as both neural transmitter and hormone. Posterior pituitary hormones include: arginine vasopressin (anti-diuretic hormone, adh) and oxytocin. They are short peptides with similar structures, indicating some gene duplication during evolution, then divergence. Divergence: oxytocin has ile and leu (no arg), whereas arginine vasopressin has phe and arg. Both affect smooth muscle tone (or muscle action)
