PowerPoint® Lecture Slides The Endocrine System: An Overview prepared by Leslie Hendon University of Alabama, Birmingham • A system of ductless glands • Secrete messenger molecules called hormones C H A P T E R 17 • Interacts closely with the nervous system Part 1 • Endocrinology The Endocrine • Study of hormones and endocrine glands System Copyright © 2011 Pearson Education, Inc. Copyright © 2011 Pearson Education, Inc. Endocrine Organs Location of the Major Endocrine Glands Pineal gland • Scattered throughout the body Hypothalamus Pituitary gland • Pure endocrine organs are the … Thyroid gland • Pituitary, pineal, thyroid, parathyroid, and adrenal Parathyroid glands glands (on dorsal aspect of thyroid gland) • Organs containing endocrine cells include: Thymus • Pancreas, thymus, gonads, and the hypothalamus Adrenal glands • Plus other organs secrete hormones (eg., kidney, stomach, intestine) Pancreas • Hypothalamus is a neuroendocrine organ • Produces hormones and has nervous functions Ovary (female) Endocrine cells are of epithelial origin • Testis (male) Copyright © 2011 Pearson Education, Inc. Copyright © 2011 Pearson Education, Inc. Figure 17.1 Hormones Control of Hormones Secretion • Classes of hormones • Amino acid–based hormones • Secretion triggered by three major types of • Steroids—derived from cholesterol stimuli: • Basic hormone action • Humoral—simplest of endocrine control mechanisms • Circulate throughout the body in blood vessels • Secretion in direct response to changing • Influences only specific tissues— those with ion or nutrient levels in the blood target cells that have receptor molecules for that hormone • Example: Parathyroid monitors calcium • A hormone can have different effects on • Responds to decline by secreting different target cells (depends on the hormone to reverse decline receptor) Copyright © 2011 Pearson Education, Inc. Copyright © 2011 Pearson Education, Inc. 1 Control of Hormones Secretion Types of Endocrine Gland Stimuli (a) Humoral stimulus (b) Neural stimulus (c) Hormonal stimulus • Secretion triggered by three major types of stimuli 1 Capillary blood contains 1 Preganglionic sympathetic fibers 1 The hypothalamus secretes low concentration of Ca2+, stimulate adrenal medulla cells… hormones that… (continued) which stimulates… CNS (spinal cord) Hypothalamus • Neural Capillary (low Ca2+ • Sympathetic nerve fibers stimulate cells in the in blood) 2 …stimulate the anterior Thyroid gland adrenal medulla pituitary gland (posterior view) Parathyroid to secrete hormones • Induces release of epinephrine and norepinephrine glands Pituitary that… gland • Hormonal Preganglionic sympathetic • Stimuli received from other glands fibers • Certain hormones signal secretion of other Thyroid Adrenal Gonad gland cortex (Testis) hormones Medulla of Parathyroid adrenal gland • Example: Hypothalamus secretes hormones glands stimulates pituitary stimulates other glands PTH Capillary 2 …secretion of parathyroid hormone 2 …to secrete catecholamines 3 …stimulate other endocrine glands (PTH) by parathyroid glands. PTH acts to (epinephrine and norepinephrine) to secrete hormones increase blood Ca2+. Copyright © 2011 Pearson Education, Inc. Copyright © 2011 Pearson Education, Inc. Figure 17.2 Control of Hormone Secretion The Pituitary Gland • Always controlled by feedback loops • Secretes nine major hormones • Blood concentration declines below a • Attached to the hypothalamus by the infundibulum minimum --> More hormone is secreted • Two basic divisions of the pituitary gland • Adenohypophysis (anterior lobe) • Blood concentration exceeds maximum • Has three major divisions --> Hormone production is halted • Pars distalis, pars intermedia, and pars tuberalis • Neurohypophysis (posterior lobe) —has two major divisions • Pars nervosa and infundibular Copyright © 2011 Pearson Education, Inc. Copyright © 2011 Pearson Education, Inc. The Pituitary Gland The Anterior Lobe Corpus callosum Thalamus • The pars distalis—largest division of the Pineal anterior lobe Hypothalamus Mammillary body • Contains five different endocrine cell groups Brain stem Pituitary (hypophysis) • Makes and secretes seven different hormones (b) Acidophil Basophil Chromophobe cell (a) • Tropic hormones regulate hormone secretion by other glands Optic chiasma Mammillary Median eminence body of hypothalamus Tuber cinereum • Include: TSH, ACTH, FSH, LH Anterior lobe Pars tuberalis Posterior lobe Pars intermedia Infundibulum • GH, PRL, and MSH Pars distalis Pars nervosa • Act directly on non-endocrine target tissues Capillary with Spherical cluster red blood cells of cells (c) (d) Copyright © 2011 Pearson Education, Inc. Figure 17.3 Copyright © 2011 Pearson Education, Inc. 2 The Anterior Lobe The Anterior Lobe • Growth hormone, GH (somatotropic • Thyroid-stimulating hormone, TSH hormone) • Produced by thyrotropic cells • Produced by somatotropic cells • Signals thyroid gland to secrete thyroid • Stimulates body growth by stimulating hormone increased protein production and growth of • Adrenocorticotropic hormone, ACTH epiphyseal plates • Stimulates the adrenal cortex to secrete • Stimulates growth directly and indirectly by hormones that help cope with stress the liver’s secretion of insulin-like growth factor-1. Copyright © 2011 Pearson Education, Inc. Copyright © 2011 Pearson Education, Inc. The Anterior Lobe The Anterior Lobe • Melanocyte-stimulating hormone, MSH • Prolactin—produced by prolactin cells • In humans, MSH functions in appetite • Targets milk-producing glands in the breast— supression stimulates milk production • Gonadotropins— are produced by • Endocrine cells of the pars distalis gonadotropic cells and affect the gonads • Clustered in spheres and branching cords • Follicle-stimulating hormone, FSH, and luteinizing hormone, LH Copyright © 2011 Pearson Education, Inc. Copyright © 2011 Pearson Education, Inc. The Anterior Lobe The Anterior Lobe Copyright © 2011 Pearson Education, Inc. Table 17.1 Copyright © 2011 Pearson Education, Inc. Table 17.1 3 Hypothalamic Control of Hormone Secretion Hypothalamic Control of Hormone Secretion from the Anterior Lobe from the Anterior Lobe • The hypothalamus • Releasing hormones • Controls secretion of anterior lobe hormones • Are secreted like neurotransmitters • Exerts control by secreting: • Enter a primary capillary plexus • Releasing hormones—prompt anterior • Travel in hypophyseal portal veins to a lobe to release hormones secondary capillary plexus • Inhibiting hormones—turn off secretion of (hypothalamohypophyseal portal system) anterior lobe hormones • From the secondary capillary plexus, hormones secreted by the anterior lobe enter general circulation and travel to target organs Copyright © 2011 Pearson Education, Inc. Copyright © 2011 Pearson Education, Inc. The Anterior Lobe The Posterior Lobe • Is structurally part of the brain • Its axons make up the hypothalamic– Hypothalamic neuron Hypothalamus 1 When appropriately cell bodies stimulated, hypothalamic hypophyseal tract Superior hypophyseal neurons secrete releasing artery and inhibiting hormones into Hypophyseal the primary capillary plexus. • Arises from neuronal cell bodies in the portal system Primary capillary hypothalamus 2 Hypothalamic hormones plexus travel through the portal Hypophyseal veins to the anterior pituitary • Supraoptic nucleus portal veins where they stimulate or Secondary inhibit release of hormones Paraventricular nucleus capillary from the anterior lobe. • plexus Anterior lobe 3 Anterior pituitary of pituitary hormones are secreted into the secondary capillary TSH, FSH, LH, plexus. ACTH, GH, PRL (a) Relationship between the anterior pituitary and the hypothalamus Copyright © 2011 Pearson Education, Inc. Figure 17.4a Copyright © 2011 Pearson Education, Inc. The Posterior Lobe Relationship Between the Posterior Pituitary and Hypothalamus • Does not make hormones 1 Hypothalamic neurons synthesize oxytocin and • Stores and releases hormones made in the ADH. hypothalamus Paraventricular nucleus Hypothalamus • Releases two peptide hormones Supraoptic nucleus 2 Oxytocin and ADH are Optic chiasma transported along the • Antidiuretic hormone (ADH) [aka, vasopressin] hypothalamic- Infundibulum (connecting stalk) hypophyseal tract to the • Oxytocin (OT) Hypothalamic- Inferior posterior lobe. hypophyseal hypophyseal tract artery 3 Oxytocin and ADH are stored in axon terminals Axon in the posterior pituitary. terminals Posterior 4 Oxytocin and ADH are lobe of Oxytocin released into the blood pituitary ADH when hypothalamic neurons fire. (b) Relationship between the posterior pituitary and the hypothalamus Copyright © 2011 Pearson Education, Inc. Copyright © 2011 Pearson Education, Inc. Figure 17.4b 4 The Posterior Lobe • ADH (vasopressin) • Made in supraoptic nucleus • Targets kidneys to reabsorb water • Oxytocin • Produced in the paraventricular nucleus • Induces smooth muscle contraction of reproductive organs, ejects milk during breast feeding, and signals contraction of the uterus during childbirth Copyright © 2011 Pearson Education, Inc. Copyright © 2011 Pearson Education, Inc. Table 17.1 The Thyroid Gland The Thyroid Gland Hyoid bone Thyroid cartilage Epiglottis • Located in the anterior neck External carotid artery • Largest pure endocrine gland Superior thyroid Common carotid artery • Composed of follicles and areolar connective artery Inferior thyroid Isthmus of artery tissue thyroid gland • Produces two hormones • Thyroid hormone (TH) Right Left subclavian subclavian artery artery • Calcitonin Left lateral