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PowerPoint® Lecture Slides Prepared by Patty Bostwick-Taylor, Florence-Darlington Technical College CHAPTER 9 The Endocrine System © 2012 Pearson Education, Inc. The Endocrine System •Second controlling system of the body •Nervous system is the fast-control system •Uses chemical messengers (hormones) that are released into the blood •Hormones control several major processes: • Reproduction • Growth and development • Mobilization of body defenses • Maintenance of much of homeostasis • Regulation of metabolism © 2012 Pearson Education, Inc. Endocrine System •https://www.youtube.com/watch?v=gjmS4_7kv DM © 2012 Pearson Education, Inc. Hormone Overview •Hormones are produced by specialized cells •Cells secrete hormones into extracellular fluids •Blood transfers hormones to target sites •The hormones then regulate the activity of other cells (aka target cells) © 2012 Pearson Education, Inc. The Chemistry of Hormones •Hormones are classified chemically as •Amino acid – based, which includes •Proteins •Peptides •Amines •Steroids — made from cholesterol •Prostaglandins — made from highly active lipids © 2012 Pearson Education, Inc. Mechanisms of Hormone Action •Hormones affect only certain tissues or organs (target cells or target organs) •Target cells must have specific protein receptors •Hormone-binding alters cellular activity © 2012 Pearson Education, Inc. Effects Caused by Hormones • (1) Changes in plasma membrane permeability or electrical state • (2) Synthesis of proteins, such as enzymes • (3) Activation or inactivation of enzymes • (4) Stimulation of mitosis • (5) Promotion of secretory activity © 2012 Pearson Education, Inc. The Chemistry of Hormones •Two mechanisms in which hormones act • I. Direct gene activation • II. Second-messenger system © 2012 Pearson Education, Inc. Steroid hormone Nucleus Cytoplasm 1 Receptor protein 2 3 Hormonereceptor complex 4 DNA mRNA 5 New protein Plasma membrane of target cell 6 (a) Steroid hormone action © 2012 Pearson Education, Inc. Figure 9.1a I. Direct Gene Activation (Steroid Hormone Action) • https://www.youtube.com/watch?v=Nm9u4lNCPyM © 2012 Pearson Education, Inc. Nonsteroid hormone (first messenger) Cytoplasm Enzyme ATP 3 1 2 Receptor protein Plasma membrane of target cell Second cAMP messenger 4 Effect on cellular function, such as glycogen breakdown (b) Nonsteroid hormone action © 2012 Pearson Education, Inc. Figure 9.1b II. Second-Messenger System (Non-steroid Hormone Action) • https://www.youtube.com/watch?v=Nt2r5R0ZO5U © 2012 Pearson Education, Inc. Control of Hormone Release •Hormone levels in the blood are mostly maintained by negative feedback •A stimulus or low hormone levels in the blood triggers the release of more hormone •Hormone release stops once an appropriate level in the blood is reached © 2012 Pearson Education, Inc. Hormonal Negative Feedback •https://www.youtube.com/watch?v=RycF0ub2 Al0 © 2012 Pearson Education, Inc. Exocrine vs. Endocrine •Exocrine: •secretes products by ducts externally to itself (outside the organ or body) • pancreas, sweat, liver, mammary •Endocrine: •release products directly into the blood stream • pancreas, and the following . . . © 2012 Pearson Education, Inc. (a) Hormonal Stimuli of Endocrine Glands •Most common stimuli •Endocrine glands are activated by other hormones • Examples: • Anterior pituitary hormones travel to target glands, such as the thyroid gland, to prompt the release of a particular hormone, such as thyroid hormone © 2012 Pearson Education, Inc. (a) Hormonal stimulus 1 The hypothalamus secretes hormones that… Hypothalamus 2 …stimulate the anterior pituitary gland to secrete hormones that… Thyroid gland Anterior pituitary gland Adrenal Gonad cortex (Testis) 3 …stimulate other endocrine glands to secrete hormones © 2012 Pearson Education, Inc. Figure 9.2a (b) Humoral Stimuli of Endocrine Glands •Changing blood levels of certain ions stimulate hormone release • Humoral indicates various body fluids such as blood and bile • Examples: • Parathyroid hormone and calcitonin are produced in response to changing levels of blood calcium levels • Insulin is produced in response to changing levels of blood glucose levels © 2012 Pearson Education, Inc. (b) Humoral stimulus 1 Capillary blood contains low concentration of Ca2+, which stimulates… Capillary (low Ca2+ in blood) Thyroid gland (posterior view) Parathyroid Parathyroid glands PTH glands 2 …secretion of parathyroid hormone (PTH) by parathyroid glands © 2012 Pearson Education, Inc. Figure 9.2b (c) Neural Stimuli of Endocrine Glands •Nerve impulses stimulate hormone release •Most are under the control of the sympathetic nervous system • Examples: • The release of norepinephrine and epinephrine by the adrenal medulla © 2012 Pearson Education, Inc. (c) Neural stimulus 1 Preganglionic sympathetic fiber stimulates adrenal medulla cells… CNS (spinal cord) Preganglionic sympathetic fibers Medulla of adrenal gland Capillary 2 …to secrete catecholamines (epinephrine and norepinephrine) © 2012 Pearson Education, Inc. Figure 9.2c