The Endocrine Syste2

The Endocrine Syste2 - Protein and peptide hormones bind to...

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The Endocrine System Receptors Chemical signals bind to receptor sites on receptor molecules to produce a response. Intracellular receptors are located in the cytoplasm or nuclei and can regulate enzyme activity or regulate the synthesis of specific messenger RNA. Membrane-bound receptors can produce a response by directly opening ion channels, activating G proteins, or activating enzymes that synthesize intracellular chemical signals, or by phosphorylating proteins inside of the cell. Hormones Endocrine glands produce hormones that are released into the circulatory system and travel some distance, where they act on target tissues to produce a response. A target tissue for a given hormone has receptor molecules for that hormone. Chemistry Hormones are basically proteins, peptides, or lipids.
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Unformatted text preview: Protein and peptide hormones bind to receptors on the cell membrane and cause permeability changes or the production of a second messenger inside the cell. Lipid-soluble hormones, such as the steroids and thyroid hormones, enter the cell and bind to receptors inside the cell. The combining of hormones with their receptors results in a response. Regulation of Hormone Secretion The secretion of hormones is controlled by negative-feedback mechanisms. Secretion of hormones from a specific gland is controlled by blood levels of some chemical, another hormone, or nervous system. The endocrine system consists of ductless glands. Some glands of the endocrine system perform more than one function....
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