Endocrine System Module 6 PDF

Module 6 Physiology of Endocrine System  Learning Objectives 6.1 Define a hormone. 6.2 List the classes of hormones and provide an example of each. 6.3 Discuss the differences between peptide and steroid hormones receptor location and mechanism of action. 6.4 Identify and discuss the functio...

Module 6 Physiology of Endocrine System  Learning Objectives 6.1 Define a hormone. 6.2 List the classes of hormones and provide an example of each. 6.3 Discuss the differences between peptide and steroid hormones receptor location and mechanism of action. 6.4 Identify and discuss the function of atypical hormones 6.5 Draw the routes of hormone action. 6.6 Describe the functions of key endocrine organs and label them on a diagram. 6.7 Outline the primary and secondary actions of Insulin & Glucagon. 6.8 Define the positive feedback loop and provide an example. 6.9 Define the negative feedback loop and provide an example.  Introduction (MO 6.1) Endocrine system- made up of a group of ductless glands that secrete “hormones”. What is a Hormone? – chemical substances – that are produced by ductless glands – released into the blood stream and carried to other parts of the body – where they produce a specific regulatory effect Classes of hormones (MO 6.2) Silverthorn, D.U. et. al.2 Copyright © 2019, 2016, 2013 Pearson Education, Inc. All rights reserved.  Peptide Hormones (MO 6.3) Receptors are found in cell membrane Response is rapid and quickly reversed as well. Secondary messengers – cellular components that bring about desired effects of hormone AFTER binding of hormone to receptor Silverthorn, D.U. et. al.2 Copyright © 2019, 2016, 2013 Pearson Education, Inc. All rights reserved.  Steroid hormones (MO 6.3) Receptors are found in cytoplasm/nucleus. Biological responses develop slowly but last longer than peptide hormones. Hormone binding triggers transcription of DNA which leads to mRNA for specific proteins to be produced. Increase in protein production brings about desired effect of hormone Silverthorn, D.U. et. al.2 Copyright © 2019, 2016, 2013 Pearson Education, Inc. All rights reserved.  Atypical Hormones (MO 6.4) (not secreted by endocrine glands) Gastrin – Wall of stomach, stimulates release of gastric juices from gastric glands for digestion to begin Secretin – Wall of SI, stimulate secretion of intestinal/pancreatic juices to continue digestion in duodenum Erythropoietin – Kidney, stimulates bone marrow  Routes of Hormone Action (MO 6.5) Endocrine route - hormone is transported via the blood to target organ Exocrine route - hormone is secreted to the exterior of the body where it interacts with a target organ (Ex: hormones secreted into the lumen of the digestive tract)  Routes of Hormone Action (MO 6.5) Paracrine route - hormone secreted into the space in between cells and the interstitial fluid carries them to the target organ (hormones often effect neighboring cells) ex. Estrogen, Testosterone. Autocrine route - hormone produced by the cell regulates the activity of the cell that produced it ex. Growth Hormone Neurocrine route - hormones diffuse through synaptic clefts similar to neurotransmitters ex. Releasing hormones Epicrine/Juxtacrine route - hormone passes through gap junctions (between) cells and alters the function of adjacent cells  ENDOCRINE ORGANS/GLANDS (MO 6.6) – Hypothalamus – Pituitary gland – Thyroid gland – Parathyroid glands – Adrenal glands – Pancreas Frandson, R.D., Wilke, W.L., Fails, A.D.1 Copyright © 2009 Wiley-Blackwell, Inc. All rights reserved.  HYPOTHALMUS (MO 6.6) Hormones 1. Releasing Hormones CRH, GnRH, GHRH, TRH Stimulates release of various hormones from adenohypophysis (anterior pituitary) 2. Oxytocin & Antidiuretic hormone Produced by Hypothalamic nuclei but stored in neurohypophysis Frandson, R.D., Wilke, W.L., Fails, A.D. Copyright © 2009 Wiley-Blackwell, Inc. All rights reserved. 1  Pituitary Gland (MO 6.6) Contains hormones that generally affect the function of many organs in a variety of systems Master Gland Two histologically distinct tissues – anterior lobe; epithelial tissue (Adenohypophysis) – posterior lobe; neural tissue (Neurohypophysis) Hormones of the Pituitary Gland (MO 6.6) Silverthorn, D.U. et. al.2 Copyright © 2019, 2016, 2013 Pearson Education, Inc. All Rights Reserved  Anterior Pituitary (Adenohypophysis) (MO 6.6) Silverthorn, D.U. et. al.2 Copyright © 2019, 2016, 2013 Pearson Education, Inc. All rights reserved.  Posterior Pituitary (Neurohypophysis) (MO 6.6) Silverthorn, D.U. et. al.2 Copyright © 2019, 2016, 2013 Pearson Education, Inc. All Rights Reserved  Thyroid Gland (MO 6.6) 1. Thyroid hormones (T4 & T3 ) – Tyrosine-based, contain iodine – T4 (thyroxine) & T3(triiodothyronine) Increase BMR Almost all tissues have receptors – (20:1) = T4 :T3 2. Calcitonin – Peptide hormone, which helps control Ca++ – Decreases blood calcium by inhibiting osteoclasts Silverthorn, D.U. et. al.2  Parathyroid Gland (MO 6.6) Most domestic animals Akers, R.M. and Denbow, D.M.3 have 2 pairs associated with the thyroid Secrete PTH – Increase blood Ca and lower blood P – Stimulates release of Ca and P from bone – increases osteocytes and osteoclasts – Promotes formation of vitamin D in kidney  Adrenal Gland (MO 6.6) 1. Adrenal Cortex – Glucocorticoids (cortisol and derivatives) - typically enhance the production (or conversion) of glucose – Mineralocorticoids (aldosterone) - regulates Na+ and K+ levels in the Silverthorn, D.U. et. al.2 Copyright © 2019, 2016, 2013 Pearson Education, Inc. All rights reserved. blood  Adrenal Gland (MO 6.6) Adrenal Medulla – Catecholamines (epinephrine and norepinephrine) - have a variety of functions in different organs, but mostly prepares animals to “flight” or Silverthorn, D.U. et. al.2 Copyright © 2019, 2016, 2013 Pearson Education, Inc. All rights reserved. “fight”  Pancreas (MO 6.6, MO 6.7) Pancreatic islets 1) Insulin (β cells) – Decreases blood glucose – Increases GTR on cells – Excess glucose becomes glycogen 2) Glucagon (α cells) – Increases blood glucose – Breaks down glucogen to free glucose molecules – Forms new glucose from amino acids Aspinall, V., Cappello, M., Phillips, C. 4 Copyright © 2009 Elsevier Health Sciences, Inc. All rights reserved.  Hormone Regulation (MO 6.8, MO 6.9) Negative Feedback Regulation – Rising levels of a hormone cause a biologic response to inhibit further release Positive Feedback Regulation – Seen less frequently than negative feedback – Hormones causes a biologic response that produces an increase in the release of hormone Aspinall, V., Cappello, M., Phillips, C. 4 Copyright © 2009 Elsevier Health Sciences, Inc. All rights reserved.  Textbooks 1. Frandson, R.D., Wilke, W.L., Fails, A.D. Anatomy and Physiology of Farm Animals (Seventh ed., 2009) ISBN: 978- 0-8138-1394-3 (Ebook- https://catalog.lib.ncsu.edu/catalog/NCSU2271719 ) 2. Silverthorn, D.E.Human Physiology: An Integrated Approach (Eight ed., 2019) (Physical copy- https://catalog.lib.ncsu.edu/catalog/NCSU4923777 ) 3. Akers, R.M. and Denbow, D.M. Anatomy and Physiology of Domestic Animals (2008) Blackwell Publishing. ISBN:978- 0-8138-0329-6 (E book- https://catalog.lib.ncsu.edu/catalog/NCSU3029855) 4. Aspinall, V., Cappello, M., Phillips, C. Introduction to veterinary anatomy and physiology (Fourth ed., 2015) (E book- https://catalog.lib.ncsu.edu/catalog/NCSU3506852)