endocrine - Endocrine system 2 types of glands: - exocrine,...

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Endocrine system 2 types of glands: - exocrine, that have ducts and release secretions onto surfaces… such as sweat glands, saliva glands, etc. - endocrine, that have no ducts and release secretions into general circulation… hormones: molecular messengers that are secreted into the general circulation, having their effect on tissues distant from where they are made. Control of endocrine secretion works by negative feedback: - a regulator cell will detect a change in the local environment… low levels of thyroid hormone for example - regulator cell will secrete a molecular messenger that will affect target cell… for example cells that produce thyroid hormone - messenger will induce increased production of thyroid hormone - this will act on regulator cell, which will decrease secreting messenger saying “make more hormone” Negative feedback… a method of keeping body in homeostasis, so will respond to low hormones by turning up production, and high by turning down. So why don’t all cells that make hormone respond directly to low or high levels of hormone? Several reasons, most of which have to do with integration of response… if there is one central command area, can make sure that the coordinated response restores homeostasis overall and not just in one aspect. Also hormones can have multiple effects on multiple tissues. Hormones are released into the general circulation, so why don’t all cells respond to them? Because only certain cells have receptors for the hormone…. receptors:
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This note was uploaded on 04/17/2008 for the course BIO 121 taught by Professor Short during the Fall '07 term at Finger Lakes Community College.

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endocrine - Endocrine system 2 types of glands: - exocrine,...

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