lec 15 integration.pptx

lec 15 integration.pptx - Principles of Hormonal...

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Page 1 Principles of Hormonal Integration 26 Endocrinological solutions to physiological problems require integration of a large variety of simultaneous events Redundancy, is the excess of regulatory capacity provided in the form of seemingly duplicative or overlapping controls Reinforcement, most hormones act at several locales either within a single cell or in different tissues or organs to produce separate but mutually reinforcing responses Push-pull mechanisms, many critical processes are under dual control by agents that act antagonistically either to stimulate or to inhibit Modulation of responding systems, or the relationship between amount of hormone available and magnitude of the response, is subjected to regulation by many factors, including the action of other hormones S ± E Introduction “story lines” and “circles intersecting circles …” S ± E how many circles do you see here ?
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Page 2 Principles of Hormonal Integration Redundancy Reinforcement Push-Pull mechanisms Modulation of Responding Systems S ± E Integration at the cellular level. A cell may receive inputs from hormones A, B, and C simultaneously. Hormone B acting through a G-protein coupled receptor activates adenylyl cyclase (AC) through the ± stimulatory subunit G ± s. Hormone C binds to its G-protein coupled receptor, which inhibits adenylyl cyclase through the inhibitory subunit G ± i, and activates phospholipase C through the G ± q subunit, resulting in cleavage of phosphatidylinositol bis-phosphate (PIP2) and the release of diacylglycerol (DAG) and inositol trisphosphate (IP3). Hormone A, acting through a tyrosine kinase receptor, activates cyclic AMP phosphodiesterase (PDE), which degrades cAMP. The combined actions of the three hormones determines the concentration of cyclic AMP. (or how responses can get complicated) Principles of Hormonal Redundancy allows for adaptation of homeostatic mechanisms to confront environmental changes Redundancy Reinforcement Push-Pull mechanisms Modulation of Responding Systems Redundancy, is the excess of regulatory capacity provided in the form of seemingly duplicative or overlapping controls Redundancy allows for physiological adaptation when partial or even total failure of an homeostatic mechanism occur and another compensates for it Strategies for therapeutic interventions, designed to increase or decrease the rate of a process, must take into account the redundant inputs that regulate that process S ± E
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Page 3 Principles of Hormonal Integration Glucagon and epinephrin, two hormones from two different tissues, produce the same end-result Redundancy Reinforcement Push-Pull mechanisms Modulation of Responding Systems (e.g. at a tissue level) S ± E Redundant mechanisms to stimulate hepatic glucose production. Hormonal and neural mechanisms are marshaled to combat potentially life-threatening low blood glucose concentrations.
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This note was uploaded on 10/19/2011 for the course ENDOCRINOL 450 taught by Professor Advis during the Spring '11 term at Rutgers.

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lec 15 integration.pptx - Principles of Hormonal...

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