Chapter 41 Endocrine

Chapter 41 Endocrine - Endocrine cells Hormones are...

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Endocrine cells Hormones are produced by an endocrine cell and are transported to distant target cells via the bloodstream. Exocrine cells produce *compounds* and secrete them via ducts to outside the body, like sweat and digestive enzymes into the gut
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Endocrine cells Many of the endocrine cells are organized into glands. Hormones are also secreted by relatively isolated cells that are not part of discrete glands , particularly in the digestive system, heart, kidneys, and adipose tissue.
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The one to many nature of endocrine communication The action of hormones depends on the nature of the receptor and the cell that harbors the receptor. A single hormone may have many different actions.
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Epinephrine For example, the hormone epinephrine (a.k.a. adrenalin) is released by the adrenal medulla in response to conditions that evoke a fight- or-flight response. This hormone has different effects on many different kinds of cells , but these diverse effects are logically integrated to serve the fight-or-flight response .
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The main endocrine glands Add Stomach , heart , . (Controls the pituitary) (The “master gland”) Parathyroid Calcium
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Types of hormones and receptors Three types of hormones Peptides or polypeptides : water-soluble, transported in blood but not across membranes. Steroid hormones : lipid-soluble; must be bound to carrier proteins to be carried in blood. Amine hormones : derivatives of tyrosine. Generally water-soluble; (e.g., epinephrine). Only one, thyroxine, is lipid-soluble Types of receptors Water-soluble hormones cannot readily pass cell membrane— receptors are on the outside Lipid soluble hormones : receptors are inside the cell
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Receptors on the membrane Amine hormones (e.g., epinephrine), peptide hormones, and melatonin bind membrane receptors. These receptors generally involve a second messenger system with cyclic AMP (cAMP) or cyclic GMP (cGMP).
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Receptors in the cytoplasm Steroid hormones: Adrenal cortex hormones Glucocorticoids Mineralocorticoids Gonadal hormones Estrogens Progestins Androgens (Also, one amine hormone, thyroxine) When the cytoplasmic receptor binds hormone, it sheds it chaperone and moves into the nucleus, where it affects gene expression.
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Hypothalamus and anterior pituitary gland The hypothalamus is the master of the master gland. Hypothalamic cells produce specific releasing hormones (and inhibiting hormones ) , which they secrete from axon terminals in the median eminence into a portal system of blood vessels to flood the anterior pituitary , causing the latter cells to release their specific hormones, some of which are tropic hormones that act on other endocrine glands .
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Depending on the need, the hypothalamus secretes varying amounts of releasing (or inhibiting) hormones to control the release of anterior pituitary hormones. In response, the anterior
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This note was uploaded on 04/19/2011 for the course LS 2 taught by Professor Pires during the Spring '08 term at UCLA.

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Chapter 41 Endocrine - Endocrine cells Hormones are...

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