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Unformatted text preview: Kevin Kelleher, MTC Biology 211 Study Notes Exam 1 1 Biology 211 Study Notes Exam 1 Chapter 16: The Endocrine System Endocrine System: a system of small glands scattered throughout the body that influences the metabolic activities of cells through hormones - Hormones: chemical messengers released to the blood by the cells of endocrine glands that regulate the metabolic activities of other cells in the body o Hormones signal target cells to perform specific chemical reactions Endocrine Glands: pituitary, thyroid, parathyroid, adrenal, pineal and thymus glands. - Organs with major functions outside the endocrine system containing endocrine tissue/cells: pancreas, gonads, hypothalamus (neuroendocrine organ) - Tissues that produce hormones also found within: adipose cells, small intestine, stomach, kidneys, heart Hormones: Amino acid-based hormones: contain from a couple to many amino acids… vary in size from simple amino acid derivatives (amines, thyroid hormone, peptides) to proteins (polypeptides) Steroid hormones: synthesized from cholesterol (includes hormones from the gonads and adrenal cortex (outer region of the adrenal gland)) Eicosanoids: local hormones (paracrines); biologically active lipids released from nearly all cell membranes - effects are highly localized, different from circulating hormones - leukotrienes: chemicals that mediate inflammation & some allergic reactions - prostaglandins: many targets/effects… raise blood pressure, stimulate uterine contractions during birth, enhance blood clotting & inflammation Eicosanoids are generally not considered part of the endocrine system, but will be discussed in later Chapters with the appropriate systems Mechanisms of hormone action: - alter plasma membrane permeability or electrical state - stimulate synthesis of proteins within cells - activate or deactivate enzymes - induce secretory activity - stimulate mitosis/cell division Amino acid-based hormones use second messenger systems - proteins and peptides cannot freely penetrate plasma membrane Kevin Kelleher, MTC Biology 211 Study Notes Exam 1 2- these hormones bind to a membrane receptor that starts a chain of reactions that activates an intracellular second messenger molecule - cyclic AMP signaling: o the hormone ( first messenger ) binds the membrane receptor; the receptor changes shape, which allows it to bind G protein o G protein is activated; binds GTP & releases GDP o activated G protein moves along membrane; binds to & activates (or inhibits) enzyme adenylate cyclase (GTP is hydrolyzed by GTPase activity of G protein) o activated adenylate cyclase converts ATP to cyclic AMP ( second messenger ); if inhibited, adenylate cyclase will not catalyze its reaction o cyclic AMP is free to circulate inside the cell; triggers activation of one to several protein kinase molecules; protein kinase phosphorylates (adds a phosphate group to) many proteins - the phosphorylated proteins may be activated or inhibited by phosphorylation - amplification effect:...
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