BIOB32H3 Lecture Notes - Thymus, Adrenal Medulla, Pars Tuberalis
28 Mar 2013
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Document Summary
Endocrine system: includes all cells and endocrine tissues that produce hormones or paracrine factors. Hormone structure: amino acid derivatives, structurally similar to amino acids, peptide hormones, chains of amino acids, lipid derivatives, steroid hormones and eicosanoids. Hormones can be: freely circulating, rapidly removed from bloodstream, bound to transport proteins. Mechanisms of hormone action: receptors for catecholamines, peptide hormones, eicosanoids are in the cell membranes of target cells, thyroid and steroid hormones cross the membrane and bind to receptors in the cytoplasm or nucleus. Hypophysis: releases nine important peptide hormones, all nine bind to membrane receptors and use cyclic amp as a second messenger. The anterior lobe (adenohypophysis: subdivided into the pars distalis, pars intermedia and pars tuberalis, at the median eminence, neurons release regulatory factors through fenestrated capillaries, releasing hormones, inhibiting hormones. Hypophyseal portal system: all blood entering the portal system will reach the intended target cells before returning to the general circulation.
