PSIO 202 Endocrine System Study Guide Introduction to Endocrine System Other organs tissues that contain endocrine cells Endocrine Gland o Pituitary o Thyroid o Parathyroid o Adrenal o Pineal o Hypothalamus o Thymus o Pancreas o Ovaries testes o Kidneys Liver o Stomach Heart Skin o Adipose tissue Endocrine vs Exocrine o Endocrine secrete products into interstitial fluid and diffuse into blood o Exocrine secrete products into ducts or lumens or to the outer surface of the body Hormones Mediator molecules released in one part of the body that regulate activity in other parts of the body o Local hormones Act locally on neighboring cells paracrine or on the same cell that secreted them autocrine without first entering the blood stream Ex IL 2 released from helper T cells stimulates proliferation of helper T cells and activation of cytotoxic T cells Ex Histamine released by mast cells stimulates HCl secretion from parietal cells in stomach o Circulating hormones Enter interstitial fluid and then the bloodstream Lipid soluble bound to transport proteins Steroid Hormones o Derived from cholesterol o Chemical groups attached to the core of the structure makes it unique o Ex cortisol testosterone estrogens progesterone aldosterone Thyroid Hormones o Tyrosine ring with attached iodines o Very lipid soluble Nitric Oxide o Hormone and neurotransmitter Water soluble free Peptide and Protein Hormones o chains of amino acids o hypothalamic releasing and inhibiting hormones o ADH oxytocin hGH TSH ACTH o Insulin glucagon EPO Biogenic amines o Modified amino acids o Catecholamines NE epinephrine dopamine o Serotonin melatonin and histamine o Derived from arachidonic acid 20 carbon fatty Eicosanoids acid o Prostaglandins and Leukotrienes o Local Hormones Functions of Hormones o Help Regulate Extracellular fluid Metabolism Biological clock Contraction of cardiac and smooth muscle Glandular secretion Some immune functions Growth and development Reproduction o Hormones only affect target cells with specific membrane or intracellular protein receptors o General mechanism of action Bind to cell surface or receptor inside target cell Cell responds via Synthesis of new molecules Change in membrane permeability Altered rates of reaction Different target cells may respond to the same hormone differently Hepatocytes insulin stimulates glycogen synthesis Adipocytes insulin stimulates triglyceride synthesis o Steroid Hormone Action Receptors typically intracellular Work by changing the level of specific gene expression o Peptide Hormone Action peptide hormones bind to cell surface receptors peptide hormones evoke changes in the activity of existing proteins through a second messenger e g cyclic AMP second messengers alter the phosphorylation state of existing proteins Second messengers o Water soluble peptide hormones bind to cell surface receptors production intracellular second messenger o Hormones first messengers may increase or decrease the level of second messengers o Ex cAMP calcium ions cGMP o Same hormone may use different second messengers in different target cells Ex Norepenephrine o Second messengers initiate a cascade of biochemical reactions often involving phosphorylation or dephosphorylation within the target cell Hypothalamus and Anterior Pituitary Hypothalamus and Pituitary Gland o Hypothalamus receives input from cortex thalamus limbic system and internal organs o Hypothalamus provides a link between the external and internal environment and the endocrine system o Hypothalamus controls the anterior pituitary gland with different releasing and inhibiting hormones o Hypothalamus releases other hormones directly through the posterior pituitary Cell types of the Anterior Pituitary o 1 Somatotrophs secrete human Grown Hormone o 2 Thyrotrophs secrete Thyroid Stimulating Hormone o 3 Lactotrophs secrete Prolactin o 4 Gonadotrophs secrete Follicle Stimulating Hormone and Lutenizing o 5 Corticotrophs secrete Adrenocorticotropic Hormone and Melanocyte Hormone Stimulating Hormone Hypothalamus Growth Hormone Releasing Hormone GHRH Growth Hormone Inhibiting Hormone GHIH or Somatostatin Gonadotropin Releasing Hormone GnRH Lutenizing Hormone LH Growth Hormone GH or Somatotropin Thyroid Stimulating Hormone TSH Growth Hormone GH or Somatotropin Anterior Pituitary Prolactin Releasing Hormone PRH Prolactin Inhibiting Hormone PIH or Dopamine Follicle Stimulating Hormone FSH Prolactin PRL Prolactin PRL Melanocyte Stimulating Hormone MSH Corticotropin Releasing Hormone CRH Thyrotropin Releasing Hormone Human Growth Hormone Adrenocorticotropic Hormone ACTH or Corticotropin Melanocyte Stimulating Hormone MSH Thyroid Stimulating Hormone TSH or Thyrotropin o Produced by somatotrophs in anterior pituitary o Target cells are liver skeletal muscle cartilage bone o Within target cells increases synthesis of insulin like growth factors that act locally or enter bloodstream o Insulin like growth factors Increase cell growth and cell division by increasing the uptake of amino acids and synthesis of proteins Stimulate lipolysis in adipose tissue so fatty acids are used for ATP Decrease use of glucose for ATP production by most body cells so blood glucose levels remain high enough to supply brain o Regulation of hGH release hGH is released in bursts every few hours release is regulated by GHRH Growth hormone releasing hormone and GHIH Growth hormone inhibiting hormone Stimuli for GHRH Hypoglycemia deep sleep decreased fatty acids and increased amino acids in blood increased sympathetic stimulation Stimuli for GHIH Hyperglycemis REM sleep increased fatty acids and decreased amino acids in blood obesity low levels of thyroid hormones high levels of hGH Follicle Stimulating Hormone FSH o Gonadotropin releasing hormone GnRH from the hypothalamus stimulates gonadotrophs in anterior pituitary to produce FSH o In females FSH Stimulates secretion of estrogen Initiates the formation of follicles within the ovary o In males FSH Stimulates sperm production in testes Luteinizing Hormone LH o GnRH from hypothalamus stimulates gonadotrophs in anterior pituitary to produce LH o In females LH stimulates Secretion of estrogen and progesterone Ovulation Formation of corpus luteum o In males LH stimulates Secretion of testosterone Prolactin dopamine o Hypothalamus regulates lactotroph cells by secreting PRH and PIH o Lactotrophs in anterior pituitary produce prolactin o Under the right conditions o Suckling reduces levels of hypothalamic