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Endocrine System Connie Dodds (Year 4) 2295723d@student.gla.ac.ukLearning Objectives • What is meant by endocrine system • 3 classes of hormone • Regulation of endocrine system through negative feedback • Development, anatomical location, structure and function of the following endocrine glands: - Pituitary - Thyroid Where is it? What hormone does it produce? - Parathyroid What effect does the hormone have? - Adrenal (suprarenal) - Pancreatic islets (islets of Langerhans)Endocrine System Introduction • Second integrative control system of the body • Much slower to act than nervous system • Actions are mediated by hormones • Controls the following regulatory systems - Regulation of cellular metabolism - Maintenance of homeostasis (e.g. Ca ++) - Sexual development and reproduction - Growth and development from childhood to adult - Modulates long term behaviour (mood, sleep)Endocrine System Introduction •Endocrine glands have no ducts, secrete and release hormones directly into blood •Hormones are “chemical messengers” that act on target cells through specific receptors Hormones in the blood • Very low concentrations in blood • Concentrations vary (e.g. episodic) • Steroid + thyroid hormones transported in blood by specific binding proteins • Improves solubility NB only free hormone is • Increases half life biologically active • Provides a reserve in the blood • Act by binding to receptors on target cells a) Cell membrane receptors: peptides, glycoproteins, catecholamines b) Intracellular receptors: steroids, thyroid hormones 3 Types of Hormones 1. PROTEINS •Chains of amino acids 2. STEROIDS •Synthesized from cholesterol 3. AMINO ACID DERIVATIVES •Thyroid hormones •CatecholaminesEndocrine regulation •Hypothalamus - secretes hormones that control the secretion of pituitary hormones •Pituitary hormones- control many other endocrine glands •Endocrine Axes/Cascades – the target tissue of one hormone is another endocrine glandPituitary gland: functions Anterior pituitary= Adenohypophysis Posterior pituitary= NeurohypophysisEndocrine Axes/Cascades Hypothalamus – Pituitary – Other endocrine glandPituitary Adenoma AcromegalyThyroid gland lies anterior to trachea in neck C5-T1Thyroid gland Development •Develops as a down growth of epithelium of the tongue (leaves a pit at the back of the tongue- foramen caecum) Thyroid Histology TRI-IODOTHYRRONINE (T3) + THYROXINE (T4) CALCITONINThyroid disorders: underactive + overactiveParathyroid glands •Adrenal glandsAdrenal Medulla •Forms from neural crest cells NEUROECTODERM •Contains CHROMAFFIN cells- produce catecholamines: -Epinephrine -Norepinephrine -Dopamine •Direct connection with sympathetic nervous system (controlling fight or flight response)Cushing’s syndrome Pancreas: exocrine and endocrine gland • Develops as an outgrowth of the gut tube 1. Exocrine PANCREATIC ACINI = produce pancreatic amylase etc (disorder- pancreatitis) 2. Endocrine ISLETS OF LANGERHANS = produce hormones - Alpha cells- glucagon - Beta cells- insulin (disorder- diabetes mellitus)Other Organs