Human Anatomy & Physiology the Endocrine System: Part A
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10/26/2014 PowerPoint® Lecture Slides Endocrine System: Overview prepared by Human Anatomy Barbara& Physiology Heard, Atlantic Cape Community • Acts with nervous system to coordinate College Ninth Edition and integrate activity of body cells • Influences metabolic activities via C H A P T E R 16 hormones transported in blood • Response slower but longer lasting than nervous system The Endocrine • Endocrinology System: Part A – Study of hormones and endocrine organs © Annie Leibovitz/Contact Press Images © 2013 Pearson Education, Inc. © 2013 Pearson Education, Inc. Endocrine System: Overview Endocrine System: Overview • Controls and integrates • Exocrine glands – Reproduction – Nonhormonal substances (sweat, saliva) – Growth and development – Have ducts to carry secretion to membrane – Maintenance of electrolyte, water, and surface nutrient balance of blood • Endocrine glands – Regulation of cellular metabolism and energy – Produce hormones balance – Lack ducts – Mobilization of body defenses © 2013 Pearson Education, Inc. © 2013 Pearson Education, Inc. Endocrine System: Overview Figure 16.1 Location of selected endocrine organs of the body. Pineal gland Hypothalamus Pituitary gland • Endocrine glands: pituitary, thyroid, Thyroid gland parathyroid, adrenal, and pineal glands Parathyroid glands (on dorsal aspect • Hypothalamus is neuroendocrine organ of thyroid gland) Thymus • Some have exocrine and endocrine functions Adrenal glands – Pancreas, gonads, placenta Pancreas • Other tissues and organs that produce hormones Gonads • Ovary (female) – Adipose cells, thymus, and cells in walls of • Testis (male) small intestine, stomach, kidneys, and heart © 2013 Pearson Education, Inc. © 2013 Pearson Education, Inc. 1 10/26/2014 Chemical Messengers Chemistry of Hormones • Hormones: long-distance chemical • Two main classes signals; travel in blood or lymph – Amino acid-based hormones • Autocrines: chemicals that exert effects • Amino acid derivatives, peptides, and proteins on same cells that secrete them – Steroids • Paracrines: locally acting chemicals that • Synthesized from cholesterol affect cells other than those that secrete • Gonadal and adrenocortical hormones them • Autocrines and paracrines are local chemical messengers; not considered part of endocrine system © 2013 Pearson Education, Inc. © 2013 Pearson Education, Inc. Mechanisms of Hormone Action Mechanisms of Hormone Action • Hormones act at receptors in one of two 2. Lipid-soluble hormones (steroid and thyroid ways, depending on their chemical nature hormones) and receptor location • Act on intracellular receptors that directly activate genes 1. Water-soluble hormones (all amino acid– • Can enter cell based hormones except thyroid hormone) • Act on plasma membrane receptors • Act via G protein second messengers • Cannot enter cell © 2013 Pearson Education, Inc. © 2013 Pearson Education, Inc. Figure 16.2 Cyclic AMP second-messenger mechanism of water-soluble hormones. Slide 1 Figure 16.3 Direct gene activation mechanism of lipid-soluble hormones. Slide 1 Steroid Extracellular Recall from Chapter 3 that hormone Plasma G protein signaling mechanisms fluid membrane are like a molecular relay race. 1 The steroid hormone Hormone Receptor G protein Enzyme 2nd diffuses through the plasma 1 Hormone (1st messenger) (1st messenger) messenger membrane and binds an binds receptor. Cytoplasm intracellular receptor. Receptor Adenylate cyclase Extracellular fluid Receptor- protein hormone complex 2 The receptor- G protein (Gs) hormone complex enters the nucleus. Receptor cAMP 5 cAMP activates Nucleus GTP protein kinases. Binding region The receptor- hormone Receptor 3 GTP complex binds a specific DNA ATP region. Inactive Active GDP GTP protein protein DNA kinase kinase 4 Binding initiates Triggers responses of transcription of the gene to target cell (activates mRNA. enzymes, stimulates mRNA cellular secretion, opens ion channel, etc.) Cytoplasm 2 Receptor 3 G protein 4 Adenylate 5 The mRNA directs protein activates G activates cyclase converts synthesis. protein (Gs). adenylate ATP to cAMP (2nd cyclase. messenger). New protein © 2013 Pearson Education, Inc. © 2013 Pearson Education, Inc. 2 10/26/2014 Target Cell Specificity Target Cell Activation • Target cells must have specific receptors • Hormones influence number of their to which hormone binds, for example receptors – ACTH receptors found only on certain cells of – Up-regulation—target cells form more adrenal cortex receptors in response to low hormone levels – Thyroxin receptors are found on nearly all – Down-regulation—target cells lose receptors cells of body in response to high hormone levels © 2013 Pearson Education, Inc. © 2013 Pearson Education, Inc. Figure 16.4a Three types of endocrine gland stimuli. Slide 1 Humoral Stimulus Neural Stimuli Hormone release caused by altered levels of certain critical ions or nutrients. Capillary (low Ca2+ • Nerve fibers stimulate hormone release in blood) – Sympathetic nervous system fibers stimulate Thyroid gland (posterior view) Parathyroid adrenal medulla to secrete catecholamines glands Parathyroid glands PTH Stimulus: Low concentration of Ca2+ in capillary blood. Response: Parathyroid glands secrete parathyroid hormone (PTH), which increases blood Ca2+. © 2013 Pearson Education, Inc. © 2013 Pearson Education, Inc. Figure 16.4b Three types of endocrine gland stimuli. Slide 1 Neural Stimulus Hormonal Stimuli Hormone release caused by neural input. CNS (spinal cord) • Hormones stimulate other endocrine organs to release their hormones – Hypothalamic hormones stimulate release of most anterior pituitary hormones Preganglionic sympathetic fibers – Anterior pituitary hormones stimulate targets to secrete still more hormones Medulla of adrenal gland – Hypothalamic-pituitary-target endocrine organ feedback loop: hormones from final target Capillary organs inhibit release of anterior pituitary Stimulus: Action potentials in preganglionic hormones sympathetic fibers to adrenal medulla. Response: Adrenal medulla cells secrete epinephrine and norepinephrine. © 2013 Pearson Education, Inc. © 2013 Pearson Education, Inc. 3 10/26/2014 Figure 16.4c Three types of endocrine gland stimuli. Slide 1 Hormonal Stimulus Nervous System Modulation Hormone release caused by another hormone (a tropic hormone). Hypothalamus • Nervous system modifies stimulation of endocrine glands and their negative feedback mechanisms Anterior pituitary gland – Example: under severe stress, hypothalamus and sympathetic nervous system activated Thyroid AdrenalGonad gland cortex (Testis) • body glucose levels rise • Nervous system can override normal endocrine controls Stimulus: Hormones from hypothalamus. Response: Anterior pituitary gland secretes hormones that stimulate other endocrine glands to secrete hormones. © 2013 Pearson Education, Inc. © 2013 Pearson Education, Inc. Duration of Hormone Activity Interaction of Hormones at Target Cells • Limited • Multiple hormones may act on same target – Ranges from 10 seconds to several hours at same time – Effects may disappear as blood levels drop – Permissiveness: one hormone cannot exert – Some persist at low blood levels its effects without another hormone being present – Synergism: more than one hormone produces same effects on target cell amplification – Antagonism: one or more hormones oppose(s) action of another hormone © 2013 Pearson Education, Inc. © 2013 Pearson Education, Inc. Figure 16.5a The hypothalamus controls release of hormones from the pituitary gland in two different ways (1 of 2). The Pituitary Gland and Hypothalamus Slide 1 Paraventricular nucleus • Pituitary gland (hypophysis) has two Hypothalamus 1 Hypothalamic neurons synthesize oxytocin or major lobes antidiuretic hormone (ADH). Posterior lobe of pituitary Optic – Posterior pituitary (lobe) chiasma Supraoptic nucleus • Neural tissue Infundibulum (connecting stalk) 2 Oxytocin and ADH are transported down the axons of Inferior the hypothalamic- hypophyseal – Anterior pituitary (lobe) Hypothalamic- hypophyseal tract to the posterior pituitary. hypophyseal artery (adenohypophysis) tract Axon terminals 3 Oxytocin and ADH are • Glandular tissue stored in axon terminals in Posterior lobe the posterior pituitary. of pituitary Oxytocin 4 When hypothalamic neurons fire, action potentials arriving at ADH the axon terminals cause oxytocin or ADH to be released into the blood. © 2013 Pearson Education, Inc. © 2013 Pearson Education, Inc. 4 10/26/2014 Figure 16.5b The hypothalamus controls release of hormones from the pituitary gland in two different ways (2 of 2). Slide 1 Posterior Pituitary and Hypothalamic Hormones Hypothalamus Hypothalamic • Oxytocin and ADH neurons synthesize GHRH, GHIH, TRH, – Each composed of nine amino acids Anterior lobe CRH, GnRH, PIH. of pituitary Superior hypophyseal – Almost identical – differ in two amino acids artery 1 When appropriately stimulated, 2 Hypothalamic hormones hypothalamic neurons secrete travel through portal veins to releasing or inhibiting hormones the anterior pituitary where into the primary capillary plexus. they stimulate or inhibit release of hormones made in Hypophyseal the anterior pituitary. portal system • Primary capillary 3 In response to releasing plexus A portal hormones, the anterior • Hypophyseal system is two pituitary secretes hormones portal veins into the secondary capillary capillary plexus. This in turn empties • Secondary plexuses into the general circulation. capillary plexus (beds) connected GH, TSH, ACTH, by veins. FSH, LH, PRL Anterior