311DCh45 - Ch 45 pg 975-994 Hormone chemical signal that is...

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Ch. 45 pg. 975-994 Hormone – chemical signal that is secreted into the circulatory system and communicates regulatory messages within the body Endocrine system – all of an animal’s hormone secreting cells Endocrine glands – hormone secreting organs; ductless glands because they secrete their chemical messengers directly into extracellular fluid; chemicals then diffuse into the circulation Neurosecretory cells – release hormones into the blood; contained in hypothalamus Negative feedback – effector response reduces the initial stimulus and the response ceases Reception – occurs when the signal molecule binds to a specific receptor protein in or on the target cell Signal transduction – binding of signal molecule to a receptor protein triggers events within the target cell Response – result; change in cell’s behavior Signal Transduction Pathway – series of changes in cellular proteins that converts an extracellular chemical signal to a specific intracellular response; activation of enzyme, change in uptake or secretion of specific molecules, or rearrangement of the cytoskeleton Paracrine signaling – local regulators convey messages between neighboring cells Cytokines – play a role in immune responses Growth factors – stimulate cell proliferation and differentiation Nitric Oxide – when blood oxygen level falls, endothelial cells in blood vessel walls synthesize and release NO; NO activates an enzyme that relaxes the neighboring smooth muscle cells which dilates the vessels and improves blood flow to tissues Prostaglandins – modified fatty acids derived from lipids in the plasma membrane; discovered in prostate gland secretions that contribute to semen; regulate nearby cells depending on the tissue; stimulate smooth muscles of uterine wall to contract so that sperm reach an egg Hypothalamus – integrates the vertebrate endocrine and nervous systems; receives
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