NURS 1109 The Endocrine System Pt 1 PDF

Instructor: Pamela Paynter-Armour  Discuss an overview of the endocrine system  Compare the endocrine and nervous systems  Identify the major glands of the endocrine system  Discuss hormones and their mechanisms of action  Discuss the term half-life as it refers to hormones ...

Instructor: Pamela Paynter-Armour  Discuss an overview of the endocrine system  Compare the endocrine and nervous systems  Identify the major glands of the endocrine system  Discuss hormones and their mechanisms of action  Discuss the term half-life as it refers to hormones  Outline the functions of the endocrine system  Describe the Pituitary Gland and the Hypothalamus  Discuss the Pituitary-Hypothalamic Relationships  Identify the Hypothalamic Hormones  Identify the Anterior Pituitary Hormones  Identify the Posterior Pituitary Hormones  Outline major homeostatic imbalances of the pituitary gland hormones 1. What is a hormone? 2. Name two endocrine glands 3. Name two functions of the endocrine system 4. Compare the endocrine and nervous systems  ENDOCRINE SYSTEM System of ductless glands Regulates body functions via hormones secreted into the bloodstream¹3 Nervous System VS. Endocrine System Nervous System Endocrine System  Controls homeostsis  Controls growth and rapidly metabolism slowly  Anatomically  Scattered: continuous: messenger molecules nerve impluse released into the EC conducted along axons space will immediately from one neuron to the enter adjacent next capillaries  Neurotransmitters  Hormones  Brief effect (muscle  Longer lasting effect contraction) with feedback loops  Endocrine system – the body’s second great controlling system which influences metabolic activities of cells by means of hormones ¹ A system of ductless glands – Secrete messenger molecules called hormones Interacts closely with the nervous system Endocrinology – Study of hormones and endocrine glands ⁷  Major Endocrine Glands Hypothalamus Pituitary Gland Thyroid Gland Parathyroid Gland Adrenal Gland Pineal Gland¹ Other organs containing endocrine tissue Pancreas Kidneys Heart Digestive Tract Placenta Testes Ovaries Thymus¹  Autocrines – chemicals that exert their effects on the same cells that secrete them  Paracrines – locally acting chemicals that affect cells other than those that secrete them  These are not considered hormones since hormones are long-distance chemical signals1 Hendon, (2008).  THE ENDOCRINE SYSTEM Like the Nervous System, the Endocrine System work through a group of chemical messengers. The endocrine messengers are called hormones. Hormones: Substances secreted by one group of cells that travel through the blood stream and regulate the metabolic functions of other cells. Hormones can affect only cells that have receptors that can bind the hormone Target cells: Those cell types that can be affected by a given hormone ¹⁰ ¹⁰ ❖ Hormones – chemical substances secreted by cells into the extracellular fluids –Regulate the metabolic function of other cells –Have lag times ranging from seconds to hours –Tend to have prolonged effects –Are classified as amino acid-based hormones, or steroids ❖ Eicosanoids – biologically active lipids with local hormone–like activity ¹  Hormones alter target cell activity by one of two mechanisms ◦ Second messengers involving:  Regulatory G proteins  Amino acid–based hormones ◦ Direct gene activation involving steroid hormones The precise response depends on the type of the target cell ¹  Hormones produce one or more of the following cellular changes in target cells ◦ Alter plasma membrane permeability ◦ Stimulate protein synthesis ◦ Activate or deactivate enzyme systems ◦ Induce secretory activity ◦ Stimulate mitosis¹  Basic categories of hormones ◦ Amino acid based: modified amino acids (or amines), peptides (short chains of amino acids), and proteins (long chains of amino acids) ◦ Steroids: lipid molecules derived from cholesterol 9  All amino acids except thyroid hormone exert their signaling effects through intracellular second messenger cyclic AMP (Cyclic adenosine monophosphate) and PIP2 Calicum (Phosphatidylinositol Biphosphate)  Steroid being lipid soluble and thyroid hormone bind directly to intracellular receptors  Hormone (first messenger) binds to its receptor, which then binds to a G protein  The G protein is then activated as it binds GTP, displacing GDP  Activated G protein activates the effector enzyme adenylate cyclase  Adenylate cyclase generates cAMP (second messenger) from ATP  cAMP activates protein kinases, which then cause cellular effects 1 ¹  Hormone binds to the receptor and activates G protein  G protein binds and activates a phospholipase enzyme  Phospholipase splits the phospholipid PIP2 into diacylglycerol (DAG) and IP3 (both act as second messengers)  DAG activates protein kinases; IP3 triggers release of Ca2+ stores  Ca2+ (third messenger) alters cellular responses ¹ ¹  Steroid hormones and thyroid hormone diffuse easily into their target cells  Once inside, they bind and activate a specific intracellular receptor  The hormone-receptor complex travels to the nucleus and binds a DNA-associated receptor protein  This interaction prompts DNA transcription to produce mRNA  The mRNA is translated into proteins, which bring about a cellular effect ¹ http://classconnection.s3.amazonaws.com/947/flashcards/1037947/png/direct_gene_activation1336152255300.png  Hormones circulate to all tissues but only activate cells referred to as target cells  Target cells must have specific receptors to which the hormone binds  These receptors may be intracellular or located on the plasma membrane ¹  Examples of hormone activity ◦ ACTH receptors are only found on certain cells of the adrenal cortex ◦ Thyroxin receptors are found on nearly all cells of the body ¹  Target cell activation depends on three factors ◦ Blood levels of the hormone ◦ Relative number of receptors on the target cell ◦ The affinity of those receptors for the hormone  Up-regulation – target cells form more receptors in response to the hormone  Down-regulation – target cells lose receptors in response to the hormone ¹ Hormones circulate in the blood in two forms – free or bound –Steroids and thyroid hormone are attached to plasma proteins –All others are unencumbered ¹ –VIDEO http://www.youtube.com/watch?v=HrMi4GikWwQ  Concentrations of circulating hormone reflect: ◦ Rate of release ◦ Speed of inactivation and removal from the body ¹  Hormones are removed from the blood by ◦ Degrading enzymes ◦ Kidneys ◦ Liver  These factors influence a hormone’s half-life ¹²  Hormones are eventually broken down (metabolized) and/or excreted from the body.  The rate of removal from the circulation is fairly constant for a given hormone.  The length of time it takes to remove half of the amount of hormone from the circulation is the half- life of that hormone 3 100% Amount of Hormone 50% 0% Time  In general, water-soluble hormones have shorter half-lives than lipid soluble hormones (rapid degradation in kidney, liver, lungs)  Hormones with short half-lives exhibit rapid changes in hormone levels3 Lipid soluble Water soluble 0 30 60 0 30 60 TIME  Three types of hormone interaction ◦ Permissiveness – one hormone cannot exert its effects without another hormone being present ◦ Synergism – more than one hormone produces the same effects on a target cell ◦ Antagonism – one or more hormones opposes the action of another hormone ¹ )  Blood levels of hormones: ◦ Are controlled by negative feedback systems ◦ Vary only within a narrow desirable range  Hormones are synthesized and released in response to: ◦ Humoral stimuli ◦ Neural stimuli ◦ Hormonal stimuli ¹  Humoral stimuli- simplest of endocrine control mechanisms ⁷ Secretion of hormones in direct response to changing blood levels of ions and nutrients Example: concentration of calcium ions in the blood – Declining blood Ca2+ concentration stimulates the parathyroid glands to secrete PTH (parathyroid hormone) – PTH causes Ca2+ concentrations to rise and the stimulus is removed ¹ (Ausin, 2004)  Neuralstimuli – nerve fibers stimulate hormone release  Preganglionic sympathetic nervous system (SNS) fibers stimulate the adrenal medulla to secrete catecholamines -epinephrine and norepinephrine ⁷  Hormonalstimuli – release of hormones in response to hormones produced by other endocrine organs ◦ The hypothalamic hormones stimulate the anterior pituitary ◦ In turn, pituitary hormones stimulate targets to secrete still more hormones ¹ (Ausin, 2004) Humoral Neural Hormonal 9  Maintenance of the internal environment in the body (maintaining the optimum biochemical environment).  Integration and regulation of growth and development.  Control, maintenance and instigation of sexual reproduction, including gametogenesis, coitus, fertilization, fetal growth and development and nourishment of the newborn 3  FUNCTIONS OF THE ENDOCRINE SYSTEM The Endocrine System helps to control and integrate: 1- Reproduction 6- Energy balance 2- Growth 7- Cellular metabolism 3- Development 4- Defense against stress 5- Water, electrolyte and nutrient balance The Endocrine system helps to maintain homeostasis by coordinating and regulating the activities of cells, tissues, organs, and systems throughout the body ¹⁰  Homeostasis It is the ability of the human body to maintain relatively stable internal conditions (temperature, PH, etc) even though the outside world changes continuously. A good homeostasis is indispensable to maintain the organism in good health. Most diseases can be regarded as a result of disturbance of homeostasis ¹⁰. Example: The body blood glucose level  FEEDBACK SYSTEMS 1- Negative feedback mechanisms: Causes the variable to change in a direction opposite to that of the initial change. or 2- Positive feedback mechanisms: Causes the variable to accelerate the change in the same direction that the initial disturbance ¹⁰ or  1- ENDOCRINE SYSTEM IN NEGATIVE FEEDBACK MECHANISMS First Hormonal Mechanism Parathyroid Stimulates the [Calcium] in hormone is osteoclasts to resorb [Calcium] in blood released by bone, releasing blood parathyroid calcium to the blood gland Second Hormonal Mechanism Calcitonin Inhibits osteoclasts to hormone is resorb bone, and [Calcium] in released by encourages calcium salt [Calcium] in blood thyroid gland deposit in bone matrix blood ¹⁰  2- ENDOCRINE SYSTEM IN POSITIVE FEEDBACK MECHANISMS Positive feedback mechanisms are used to amplify or perpetuate events. They are referred as “cascades”. Example: HYPOTALAMUS SENSOR CONTROL CENTER OXYTOXIN EFFECTOR DELIVERY! Uterine PITUITARY GLAND contractions ¹⁰  The nervous system modifies the stimulation of endocrine glands and their negative feedback mechanisms  The nervous system can override normal endocrine controls ◦ For example, control of blood glucose levels  Normally the endocrine system maintains blood glucose  Under stress, the body needs more glucose  The hypothalamus and the sympathetic nervous system are activated to supply ample glucose ¹ Control of Hormone Secretion Most of hormone secretions are controlled by the Hypothalamus and the Pituitary gland Hypothalamus Pituitary gland ¹⁰ Corpus callosum Septum pellucidum Fornix Intermediate mass Thalamus Epi- thalamus Pineal gland Anterior commissure Optic chiasm Pituitary gland Hypothalamus Mamillary body ¹⁰  Neuro-endocrine gland  Controls the pituitary gland  Receives information from the nervous system ⁸  HYPOTHALAMUS ‘Master Gland’ Monitors composition Function : Control & temperature of blood centre Messages interpreted, Attached to roof of evaluated : outgoing third ventricle, near messages dispatched thalamus via nerves / hormones Continuously receive Plays role in feedback information on status systems that govern of body systems via secretions of endocrine nerve impulses system¹  Pituitary Gland Pea sized mass of glandular tissue Lies in sella turcica Slender stalk: Infundibulum connects pituitary gland to hypothalamus 2 parts : Neurohypophysis Adenohypophysis ¹  Indirectly controls : Growth Metabolism Sexual reproduction Lactation¹  Pituitary gland – two-lobed organ that secretes nine major hormones  Neurohypophysis – posterior lobe (neural tissue) and the infundibulum ◦ Receives, stores, and releases hormones from the hypothalamus  Adenohypophysis – anterior lobe, made up of glandular tissue ◦ Synthesizes and secretes a number of hormones ¹ (Ausin, 2004)  The posterior lobe is a down growth of hypothalamic neural tissue  Has a neural connection with the hypothalamus (hypothalamic-hypophyseal tract)  Nuclei of the hypothalamus synthesize oxytocin and antidiuretic hormone (ADH)  These hormones are transported to the posterior pituitary ¹  The anterior lobe of the pituitary is an outpocketing of the oral mucosa  There is no direct neural contact with the hypothalamus ¹  The six hormones of the adenohypophysis (anterior pituitary): ◦ Are abbreviated as GH, TSH, ACTH, FSH, LH, and PRL ◦ Regulate the activity of other endocrine glands  In addition, pro-opiomelanocortin (POMC): ◦ Has been isolated from the pituitary ◦ Is enzymatically split into ACTH, opiates, and MSH ¹  TSH: thyroid-stimulating hormone  ACTH: adrenocorticotropic hormone  FSH: follicle-stimulating hormone  LH: luteinizing hormone  GH: growth hormone  PRL: prolactin  MSH: melanocyte-stimulating hormone  ADH: antidiuretic hormone  Oxytocin 9  Releasing hormones (releasing factors) Secreted like neurotransmitters from neuronal axons into capillaries and veins to anterior pituitary (adenohypophysis) TRH-----turns on TSH CRH-----turns on ACTH GnRH (=LHRH)---turns on FSH and LH PRF (eg TRH) -----turns on PRL GHRH----turns on GH  Inhibiting hormones PIH-----turns off PRL GHIH ---turns off GH 9  Releasing hormones (releasing factors) of hypothalamus Secreted like neurotransmitters from neuronal axons into capillaries and veins to anterior pituitary (adenohypophysis) TRH (thyrotropin releasing hormone) -----turns on* TSH CRH (corticotropin releasing hormone) -----turns on ACTH GnRH (gonadotropin releasing hormone) ---turns on FSH and LH PRF (prolactin releasing factor) -----turns on PRL GHRH (growth hormone releasing hormone) ----turns on GH  Inhibiting hormones of hypothalmus PIH (prolactin inhibiting hormone) -----turns off PRL GH (growth hormone) inhibiting hormone ---turns off GH The hypothalamus controls secretion of hormones which in their turn control the secretion of hormones by the thyroid gland, the adrenal cortex and gonads: in this way the brain controls these endocrine glands 9 *Note: “turns on” means causes to be released  The hypothalamus sends a chemical stimulus to the anterior pituitary ◦ Releasing hormones stimulate the synthesis and release of hormones ◦ Inhibiting hormones shut off the synthesis and release of hormones ¹ 3  Produced by somatotropic cells of the anterior lobe that: ◦ Stimulate most cells, but target bone and skeletal muscle ◦ Promote protein synthesis and encourage the use of fats for fuel  Most effects are mediated indirectly by somatomedins (Insulin-Like Growth Factors (IGFs)) ¹  Antagonistic hypothalamic hormones regulate GH ◦ Growth hormone–releasing hormone (GHRH) stimulates GH release ◦ Growth hormone–inhibiting hormone (GHIH) inhibits GH release ¹  GH stimulates liver, skeletal muscle, bone, and cartilage to produce insulin-like growth factors  Direct action promotes lipolysis and inhibits glucose uptake ¹ (Ausin, 2004)  Tropic hormone that stimulates the normal development and secretory activity of the thyroid gland  Triggered by hypothalamic peptide thyrotropin-releasing hormone (TRH)  Rising blood levels of thyroid hormones act on the pituitary and hypothalamus to block the release of TSH ¹  Stimulates the adrenal cortex to release corticosteroids  Triggered by hypothalamic corticotropin- releasing hormone (CRH) in a daily rhythm  Internal and external factors such as fever, hypoglycemia, and stressors can trigger the release of CRH ¹  Gonadotropins – follicle-stimulating hormone (FSH) and luteinizing hormone (LH) ◦ Regulate the function of the ovaries and testes ◦ FSH stimulates gamete (egg or sperm) production ◦ Absent from the blood in prepubertal boys and girls ◦ Triggered by the hypothalamic gonadotropin- releasing hormone (GnRH) during and after puberty ¹  In females ◦ LH works with FSH to cause maturation of the ovarian follicle ◦ LH works alone to trigger ovulation (expulsion of the egg from the follicle) ◦ LH promotes synthesis and release of estrogens and progesterone ¹  In males ◦ LH stimulates interstitial cells of the testes to produce testosterone ◦ LH is also referred to as interstitial cell-stimulating hormone (ICSH) ¹  In females, stimulates milk production by the breasts  Triggered by the inhibition hypothalamic prolactin-inhibiting hormone (PIH)  Inhibited by increase prolactin-inhibiting hormone (PIH)  Blood levels rise toward the end of pregnancy  Suckling stimulates PRFs release and encourages continued milk production ¹  Structurally part of the brain  Secretes two hormones ◦ Antidiuretic hormone (ADH) ◦ Oxytocin ⁷  Posterior pituitary – made of axons of hypothalamic neurons, stores antidiuretic hormone (ADH) and oxytocin  ADH and oxytocin are synthesized in the hypothalamus  ADH influences water balance  Oxytocin stimulates smooth muscle contraction in breasts and uterus  Both use PIP2-calcium second-messenger mechanism ¹  Let’s go over these one at a time... Growth hormone Prolactin Stimulates milk production Stimulates increase in size of muscles and bones Anterior Thyroid-stimulating Luteinizing Lobe Stimulates the thyroid Females: stimulates ovulation gland to release its and estrogen production hormones Males: stimulates testosterone Follicle-stimulating production Adrenocorticotropic Females: stimulates estrogen production and maturation of the ova Stimulates the adrenal cortex Males: stimulates sperm production to release its hormones  Oxytocin Posterior Females: causes contraction of the uterus and ejection Lobe of breast milk Males: stimulates contraction of the prostate and vas deferens during sexual arousal Antidiuretic hormone (ADH) Stimulates the kidneys to conserve water http://02varvara.files.wordpress.com/2012/09/00-here-we-go-again-09-12.jpg https://encrypted-tbn2.gstatic.com/images?q=tbn:ANd9GcTM-2zk6gR4k-eAJIGBUrnc4XHPeM0hlpZ7uKw-y6WMxsGnFHuJ 3 mechanisms of Hypothalamic Control over Endocrine Function ¹⁰  Posterior lobe Anterior lobe TSH, FSH, LH, ACTH, GH, PRL, MSH Oxytoxin and Antidiuretic ¹⁰ Hormone (ADH) PITUITARY GLAND: PARTS Neurohypophysis Adenohypophysis Small posterior lobe Large anterior lobe Stores hormones Make & Releases hormones Oxytocin Growth hormone (GH) Anti Diuretic hormone Thyroid Stimulating hormone (ADH) (TSH) Adenocorticotropic hormone (ACTH) Lutenizing hormone (LH) Follicle stimulating hormone (FSH) Melanocyte stimulating hormone (MSH) Prolactin (PRL) (¹) PITUITARY GLAND: HORMONES HORMONES EFFECTS Anterior Posterior Oxytocin (OC) Stimulates contraction of uterus & contractile Pituitary cells of breast ADH Prevents excess urine production GH General body growth ACTH Stimulate adrenal cortex to release hormone TSH Controls thyroid gland Anterior Posterior Pituitary LH Stimulates sexual & reproductive function FSH Stimulate production of sperm & egg in ovaries & testis MSH Related to appetite control /skin pigmentation PRL Initiates milk production in breast Hormones produced by the Hypothalamus and released by the posterior pituitary ¹⁰ Hormonal Control of Water Retention in the Body The body controls how much water is either sent to the bladder (in urine) or retained in circulation through a hormone called “antidiuretic hormone” (ADH) When the body needs water, osmoreceptors in the hypothalamus sense the increase of solute concentration in the blood, and the hypothalamus orders the release of ADH from the pituitary gland. ADH works on the distal nephron tubule and the collecting duct increasing their permeability to water. Consequently, more water moves out of the nephron tubule and collecting duct and thus back into circulation ¹⁰ ¹⁰ Hendon, (2008).  https://encrypted-tbn1.gstatic.com/images?q=tbn:ANd9GcQdb4-Zznhbo9Je_tq9DHveePhMY07S2LPpahbtDLGMxVz9CclIVw  Gigantism ◦ Hypersecretion of GH in children  Acromegaly - hypersecretion of GH in adults  Pituitary dwarfism ◦ Hyposecretion of GH  Diabetes insipidus ◦ Inadequate ADH produced and released ◦ (⁵) Match the following: ANSWER: D, ___ E Stored in posterior pituitary A. Follicle-stimulating hormone ___ B Milk production B. Prolactin D, ___ E Produced by hypothalmus C. Luteinizing hormone ___ A Stimulates sperm production D. ADH ___ A Maturation of ova E. Oxytocin ___ C Stimulates ovulation ___ D Conservation of water ___ C Production of testosterone ___ E Contraction of uterus Super! (2). Match the following: ANSWER: E ___ Chemicals that effect cell function A. Nonsteroidal hormone B ___ Easily cross cell membranes B. Steroidal hormone A ___ Made of amino acids C. G-protein D ___ Target nearby cells D. Prostaglandins C ___ Activated by hormone-receptor E. Hormones complex A ___ Cannot cross cell membranes easily B ___ Estrogen and cortisol VERY GOOD! 1. Austin, V. (2004). The Endocrine System. Retrieved from http://www.google.tt/url?sa=t&rct=j&q=&esrc=s&frm=1&s ource=web&cd=6&ved=0CEUQFjAF&url=http%3A%2F%2Fiws.collin.edu%2Fapetersonford%2F2402%2520C70%2FExam%2 520Unit%25201%2FChapter%252016%2520part%25201.pptx &ei=tea-Up7lKeSIygHt74DICw&usg=AFQjCNGNw3kGIT- MT3kz4aOaJFVCeOZx9Q 2. Booth, Whicker, Wyman, Pugh, Thompson. (2009). The Endocrine System. 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