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Unformatted text preview: Lecture 36: Principles of Endocrinology Reading: review chapter 4: principles of hormonal communication and comparison of nervous and endocrine systems (the are listed as general principles of endocrinology and occur at beginning of chapter 18 in 5 th edition) chapter 18: up to but not including hypothalamus and pituitary (same if using 6 th edition) (up to but not including pineal gland and circadian rhythms if using 5 th edition) Endocrinology Study of the control of physiological processes by the system of cells, tissues, organs and glands that secrete hormones. Hormone Chemical produced by one cell which enters the bloodstream, is transported to a different body location, and then binds to a specific receptor on a target cell(s), altering function of the target. Human body has two major control systems: Nervous system Endocrine system- rapid, short-acting signals - slower acting, longer lasting signal - precise, direct interconnections - diffuse, indirect connections (via blood) Endocrine signaling ( Figure 18-4, 5 th edition only ): endocrine gland -> hormone -> receptor binding -> postreceptor events -> response General functions of endocrine system (1) Homesostasis - regulates composition and volume of ECF - controls energy production - controls digestive tract and organ function - induces adaptation to hostile environment (2) Reproduction (3) Growth and development (4) Behavior Hormones Tropic hormones stimulate and maintain their endocrine target tissues e.g. thyroid stimulating hormone (TSH). TSH is derived from the anterior pituitary and acts on the thyroid gland to stimulate secretion of thyroid hormone. It is also responsible for maintaining the thyroid gland. Therefore a decrease in TSH will lead both to decreased production of thyroid hormone and to atrophy of the thyroid gland (it shrinks). Non-tropic hormones exert effects on non-endocrine target tissue e.g. thyroid hormone acts on almost every cell in the body to regulate metabolic activity. Criteria for determining if a substance is a hormone - gland removal leads to a specific homeostatic problem (i.e. remove adrenal cortex, excessive Na loss, death) - extracts from gland correct problem - purified synthetic hormones correct problem - time-course of hormone release is physiologically relevant 3 Classes of Hormones Peptides and proteins - small chains of amino acids (3-200 aa long) - synthesis: transcription and translation - processed in Golgi complex - Cleave pre and pro portions - mature hormones stored in secretory granules until released by exocytosis - are hydrophilic (water soluble) Amines Are derived from naturally occurring amino acids Examples: tyrosine -> thyroid hormones (in thyroid gland) tyrosine -> epinephrine (in adrenal medulla) tryptophan -> melatonin (in pineal gland) Steroids - derived from cholesterol- lipophilic (fat soluble)- once synthesized, steroid immediately diffuse through the plasma membrane into blood- in blood, reversibly bound to plasma proteins...
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This note was uploaded on 01/29/2012 for the course NPB 101 taught by Professor Fuller,charles/goldberg,jack during the Winter '08 term at UC Davis.
- Winter '08