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This 3 page Class Notes was uploaded by Jess Graff on Wednesday February 17, 2016. The Class Notes belongs to BMS 508 at University of New Hampshire taught by Mary Katherine Lockwood, PhD in Spring 2016. Since its upload, it has received 9 views. For similar materials see Human Anatomy and Physiology II in Biological Sciences at University of New Hampshire.
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Date Created: 02/17/16
BMS 508.03 2/1/2016 Chapter 18 (cont) Endocrine System (cont) The Pituitary Gland (cont) • The Posterior Lobe of the Pituitary Gland • Also called neurohypophysis • Contains unmyelinated axons of hypothalamic neurons • Supraoptic and paraventricular nuclei manufacture: • Antidiuretic hormone (ADH) • Oxytocin (OXT) The Thyroid Gland • The Thyroid Gland • Lies inferior to thyroid cartilage of larynx • Consists of 2 lobes connected by narrow isthmus • Thyroid follicles • Hollow spheres lined by cuboidal epithelium • Cells surround follicle cavity that contains viscous colloid • Surrounded by network of capillaries that: • Deliver nutrients and regulatory hormones • Accept secretory products and metabolic wastes • Thyroglobulin (Globular Protein) • Synthesized by follicle cells • Secreted into colloid of thyroid follicles • Molecules contain the amino acid tyrosine • Thyroxine (T ) 4 • Also called tetraiodothyronine • Contains 4 iodide ions • Triiodothyronine (T ) 3 • Contains 3 iodide ions • Thyroid-binding Globulins (TBGs) • Plasma proteins that bind about 75% of T and 70% o4 T entering the 3 bloodstream • Transthyretin (thyroid-binding prealbumin – TBPA) and albumin • Bind most of the remaining thyroid hormones • About 0.3% of T and 0.03% of T are unbound 3 4 • Thyroid-Stimulating Hormone (TSH) • Absence causes thyroid follicles to become inactive • Neither synthesis nor secretion occurs • Binds to membrane receptors • Activates key enzymes in thyroid hormone production • Functions of Thyroid Hormones • Thyroid Hormones • Enter target cells by transport system • Affect most cells in body • Bind to receptors in: • Cytoplasm • Surfaces of mitochondria • Nucleus • In children, essential to normal development of: • Skeletal, muscular, and nervous systems • Calorigenic Effect • Cell consumes more energy resulting in increased heat generation • Is responsible for strong, immediate, and short-lived increase in rate of cellular metabolism • Effects of Thyroid Hormones on Peripheral Tissues 1. Elevates rates of oxygen consumption and energy consumption; in children, may cause a rise in body temperature 2. Increases heart rate and force of contraction; generally results in a rise in blood pressure 3. Increases sensitivity to sympathetic stimulation 4. Maintains normal sensitivity of respiratory centers to changes in oxygen and carbon dioxide concentrations 5. Stimulates red blood cell formation and thus enhances oxygen delivery 6. Stimulates activity in other endocrine tissues 7. Accelerates turnover of minerals in bone • The C Cells of the Thyroid Gland and Calcitonin 1. C (clear) cells also called parafollicular cells 2. Produce calcitonin (CT) • Helps regulate concentrations of Ca 2+ in body fluids • Inhibits osteoclasts, which slows the rate of Ca 2+ release from bone 2+ • Stimulates Ca excretion by the kidneys Parathyroid Glands • 4 Parathyroid Glands • Embedded in the posterior surface of the thyroid gland • Altogether, the 4 glands weigh 1.6 g • Parathyroid Hormone (PTH) or parathormone • Produced by parathyroid (chief) cells in response to low concentrations of Ca 2+ • Antagonist for calcitonin
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