Endocrine System PDF

ENDOCRINE SYSTEM PRINCIPLES OF CHEMICAL Functions of the Endocrine System (MC3I2 COMMUNICATION WHUT) Chemical messengers – allow cells to 1. Metabolism. communicate with each other...

ENDOCRINE SYSTEM PRINCIPLES OF CHEMICAL Functions of the Endocrine System (MC3I2 COMMUNICATION WHUT) Chemical messengers – allow cells to 1. Metabolism. communicate with each other 2. Control of blood glucose and other Secretion – controlled release of chemicals nutrients. from a cell 3. Control of reproductive functions. 4. Control of food intake and digestion. 5. Ion regulation. 6. Immune system regulation. 7. Water balance. 8. Heart rate and blood pressure regulation. 9. Uterine contraction and milk release. 10. Tissue development. Characteristics of the Endocrine System Endocrine System – composed of endocrine glands + endocrine specialized cells Hormones – chemical messenger that is secreted into the blood Target tissues – effectors; specific site Endocrine – Greek word; endo (within) + Classes of Chemical Messengers krino (secrete); ductless glands that directly 1. Autocrine – stimulates the cell that secretes their products into the blood stream. originally secreted it; WBCs during an Exocrine glands – have ducts that carry their infection secretions to the outside of the body; drains 2. Paracrine – act locally on nearby their secretions through a duct to the outside of cells; WBCs during allergic reactions the body or into a holloworgan 3. Neurotransmitter – activate an Endocrinology – study of the endocrine adjacent cell system 4. Endocrine – secreted into the HORMONES bloodstream by certain glands and Hormones are chemical messengers cells that are secreted directly to the blood stream by endocrine glands or specialized endocrine cells. From the blood stream, they travel to the effectors or target cells to produce a response. Components of Hormones Receptor site - location on a cell where hormone binds (lock) Target tissues - group of cells that respond to specific hormones Specificity - specific hormones bind to specific receptor sites Hormones influence their target cells by chemically binding to specific  protein receptors, a property termed as 2. Neural Stimuli – nervous system; selectivity. neurons response to an action potential In the occurrence of excess hormones and release neurotransmitters and/or in the blood stream, the receptors of neuropeptides to stimulate endocrine the target-cell decrease, a cells. phenomenon called downregulation ❖ Releasing hormones is a term that makes the cell less-sensitive to the used for hormones of hormone. hypothalamus because it Insufficient amounts of hormones in stimulates hormone secretion the blood causes the target-cells’ of other endocrine cells receptors to multiply, an effect called 3. Hormonal Stimuli – hormones; the up-regulation which makes the cell hormone secreted by an endocrine more-sensitive to the hormones. gland stimulates the release of other hormones ❖ Tropic hormones are produced from the anterior pituitary gland that causes other endocrine gland to release hormones. Inhibition of Hormone Release A process that occurs to counteract the stimulating effect of three types of stimuli: humoral, neural, and hormonal. 1. Humoral inhibition - opposes and How does this work? counteract the effect of humoral 1. Hormones are secreted by endocrine stimulus glands directly into bloodstream 2. Neural inhibition: inhibitory 2. Hormones travel to all parts of body neurotransmitters prevents the 3. Hormones (key) bind to receptor site endocrine gland from secreting its (lock) on target tissue hormone 4. Response occurs 3. Hormonal inhibition: certain How does hormones cause change? hormones block the release of other Alter cell activity of target tissues by hormones. increasing or decreasing cell’s normal ❖ Inhibiting hormones are processes produced by the Change permeability of cell hypothalamus to prevent the membrane by opening or closing ion pituitary gland to release channels tropic hormones. Synthesis of proteins Negative Feedback Loop Chemical Nature of Hormones Regulates hormone secretion by the 1. Lipid-Soluble - includes steroids and hypothalamus and pituitary gland eicosanoids Increased amounts of target gland 2. Water-Soluble– includes proteins; hormones in the bloodstream decrease peptides, amino acids; most common. secretion of the same hormone and Control Of Hormone Secretion other hormones that stimulate its Stimulation of Hormone Release release. 1. Humoral Stimuli – blood levels of chemicals; response to certain levels of substance in the blood.  Major link between the nervous and endocrine systems. What Hormones Does It Produce and What For? ❖ Termed as the endocrine control center of the brain ❖ Produces nine different hormones. Regulation of Hormone Levels in the Blood A. Negative feedback ❖ Blood conc. of hormone declines ❖ More hormone is secreted ❖ If max. set point is exceeded Anterior Pituitary ❖ Hormone production is halted 1. Growth hormone (GH) B. Positive feedback Affects body growth by stimulating ❖ Tropic hormones stimulate the release protein synthesis by increasing gene of other hormones expression Hormone Receptors and Mechanisms of Breakdown of lipids Action Release of fatty acids from cells Receptors – where hormones exert action by Increases blood glucose levels binding to proteins Pituitary dwarf – deficiency in GH although Receptor site – the portion of each receptor normally proportioned molecule where a hormone bind Gigantism – excess GH; exaggerated bone Specificity – tendency of hormones to bind to growth occurs one type of receptor Acromegaly – abnormally large facial features Target tissue – the responding tissue based on & hands the hormone released Insulin-like growth factors (IGFs) Classes of Receptors 2. Thyroid-stimulating hormone (TSH) 1. LSH bind to nuclear receptors. Promotes synthesis and secretion of ❖ Interaction with cell DNA to regulate thyroid hormone transcription. 3. Adrenocorticotropic hormone (ACTH) 2. WSH bind to membrane bound Increases secretion of glucocorticoid receptors. hormones ❖ Hormone receptor complex initiates a Increases skin pigmentation response inside the cell (G proteins, 4. Melanocyte-stimulating hormone (MSH) cAMP, protein kinase). Increases melanin prod. in ENDOCRINE GLANDS AND THEIR melanocytes HORMONES 5. Luteinizing hormone (LH) Hypothalamus Promotes ovulation and progesterone Portion of the diencephalon of the production on ovary brain, forming the floor and part of the Interstitial cell-stimulating hormone lateral wall of the third ventricle; (ICSH) region below the thalamus. Promotes testosterone synthesis and Major link between the nervous and support for sperm cell prod. in testis endocrine systems. 6. Follicle-stimulating hormone (FSH) Termed as the endocrine control Promotes follicle maturation and center of the brain estrogen secretion in ovary  Promotes sperm cell prod. in testis In 50% of the cases, it has a third lobe 7. Prolactin called pyramidal lobe that extends Promote development of breast during superiorly to the isthmus pregnancy Stimulates milk prod. and prolongs progesterone secretion Increases sensitivity to LH in males 8. Antidiuretic hormone Conserves water Constricts blood vessels Syndrome of Inappropriate ADH (SIADH) Diabetes Inspidus – large prod. of dilute urine 9. Oxytocin Swift birth Increases uterine contractions Increases milk letdown Pituitary Gland A small gland about the size of a pea Controls the functions of many other glands Secrets hormones that influence growth, kidney function, birth, milk prod. Formerly called “Master Gland” 1. Calcitonin Decreases rate of bone breakdown Prevents large increase in blood Ca2+ 3 portions of PG levels Anterior pituitary gland 2. Thyroid hormones (adenohypophysis)- produces eight Increases metabolic rates hormones; has five cell types that Essential for normal process of growth produce a specific hormone Thyroxine / Tetraiodothyronine - contains (somatotrophs, thyrotrophs, four iodine atoms gonadotrophs, lactotrophs, and ❖ Increase basal metabolic rate (BMR) corticotrophs.) ❖ Enhance actions of catecholamines Posterior pituitary gland ❖ Regulate development of nervous and (neurohypophysis) - stores two bone tissues hormones; Posterior pituitary gland Triiodothyronine – contains three iodine stores and release two hormones, atoms produced by the hypothalamus. Isthmus – narrow band that connects the two Thyroid Gland lobes of the thyroid gland A shield-shaped organs located Thyroid follicles – where thyroid hormones inferior to the larynx. are synthesized and stored Typically, it has two lobes, located Goiter – excess TSH; low in iodine diet laterally to the trachea. Hypothyroidism – lack of thyroid hormones Cretinism – congenital absence of thyroxine Hyperparathyroidism (Hypercalcemia) – in infants abnormally high rate of PTH secretion Myxedema – accumulation of fluid and other ❖ Tumor molecules in subcutaneous tissue in adults ❖ Muscle weakness Hyperthyroidism – elevated rate of thyroid ❖ Soft, easily deformed bones hormone secretion ❖ Prone to kidney stone formation Graves’ disease – hyperthyroidism that results Hypoparathyroidism (Hypocalcemia) – when the immune system produces abnormal abnormally low rate of PTH; surgery proteins ❖ Surgery Exophthalmia – bulging of the eye ❖ Frequent muscle cramps or tetanus ❖ Respiratory arrest ❖ CHVOSTEK’s sign & TROSSEAU sign How does it produce hormone? ❖ PTH and calcitonin have an antagonistic effect and are both regulated via negative feedback system as initiated by the serum calcium level. ❖ ↑Ca in blood = inhibits PTH secretion ❖ ↓Ca in blood = stimulates PTH secretion Parathyroid Gland Four, small, round structures that are partially embedded in the posterior surface of the lateral lobes of the thyroid gland. Chief/principal cells in the parathyroid gland produce the parathyroid hormone (PTH) or parathormone. Adrenal Gland Two, flattened pyramidal glands located superior to each kidney. Divided into two portions: adrenal cortex (outer) and adrenal medulla (inner). 1. Parathyroid hormone Increase Ca+ levels in the blood Increases rate of bone breakdown by osteoclasts Increases vit. D synthesis (essential for of normal blood calcium levels) Adrenal Medulla 1. Epinephrine (Adrenalin) & Norepinephrine Fight-or-flight hormones Increases cardiac output Increases blood flow to skeletal muscles & heart Increases release of glucose and fatty acids into blood Prepares body for physical activity Adrenal Cortex 3 ZONES THAT PRODUCE HORMONE ❖ Functions include: protein and lipid 1. Aldosterone (Mineralocorticoids) breakdown, glucose formation Regulates water balance (gluconeogenesis), stress resistance, Increases rate of Na transport into anti-inflammatory response, and body immune suppresion. Increase rate of K excretion ❖ Androgens, mainly Renin – protein molecule that acts as an dehydroepiandrosterone (DHEA), enzyme stimulates axillary and pubic hairs Renin Angiotensin Aldosterone System formation, female libido, and is (RAAS) – helps the body to address responsible for post-menopausal decreasing blood volume estrogen production. 2. Cortisol (Glucocorticoids) ❖ All female estrogen comes from Increase fat & protein breakdown androgen. Increase glucose synthesis from amino ❖ ACTH governs the regulation of acids androgens. Increase blood nutrient levels II. Adrenal medulla is a modified Inhibit inflammation & immune sympathetic ganglion of the SNS. response ❖ Instead of producing Helps the body in stressful situations neurotransmitters, the chromaffin by providing energy sources cells of theadrenal medulla secrete Cortisone – artificial cortisol; anti- hormones: Epinephrine and inflammatory Norepinephrine. effect ❖ Autonomic Nervous System (ANS) 3. Androgens has a direct control over the secretion Male sex hormone; stimulates the of epinephrine and norpinephrine that dev’t of male characteristics enhance the effect of SNS. Increases female sex drive ❖ During stressful situation or exercise, Addison’s disease – hyposecretion of adrenal the hypothalamus stimulates the cortex hormones sympathetic preganglionic neurons to Cushing’s disease – tumor in middle cortex stimulate chromaffin cells to produce Hyperaldosteronism – hyperactivity of outer epinephrine and norepinephrine. Cortex THYMUS Hirsutism – masculinization (inner cortex) A bilobed gland, What does it produce and what for? roughly triangular in I. Adrenal cortex has three zones that shape, located in the produces different hormones: superior mediastinum, ❖ Glucocorticoids, mainly cortisol behind the sternum (hydrocortisone), regulates between the lungs. metabolism and resistance to stress. What hormones does it produce and what for? What hormone does it produce and what It produces the hormones: thymosin, for? thymo-humoral factor (THF), thymic A (alpha) cells = produce glucagon to factor (TF), and thymopoietin. All of increase glucose level in the blood and which promotes the maturation of T to stimulate insulin production. cells B (beta) cells = produce insulin to 1. Thymosin increase glucose uptake of cells; Promotes immune system thereby, lowering blood glucose level. development and function It also inhibits glucagon production. Helps the dev’t of certain WBC (T- D (delta) cells = produce somatostatin cells) that inhibits glucagon and insulin Pineal Gland secretion. It also slows down A small, pinecone-shaped structure nutrients’ absorption in the intestines. located superior and posterior to the F cells = produce pancreatic thalamus of the brain. polypeptide which inhibits What hormone does it produce and what for? somatostatin secretion. It produces the hormone melatonin. Melatonin is thought to have two functions: ❖ 1. Sleep-wake cycle ❖ 2. Inhibits the functions of the reproductive system 1. Melatonin Inhibits secretion of gonadotropin- releasing hormone (thus inhibits reproduction) Biological clock (day & night cycle) Pancreas Both endocrine and exocrine gland. Located in the first curve of the duodenum and is consist of head, tail, and body. Endocrine tissues are called endocrine islets which include: A cells, B cells, D cells, and F cells 1. Insulin Secreted by beta cells Increases uptake and use of glucose and amino acids  Released in response to elevated blood glucose level & parasympathetic stimulation 2. Glucagon Secreted by alpha cells Increases breakdown of glycogen and release of glucose into the circulatory system Released in response to low blood glucose level OVARIES Glycogen – stored glucose in muscles & liver 1. Estrogen & Progesterone Acidosis – reduced pH of body fluids Aid in uterine and mammary gland Satiety center – area of the hypothalamus that development and function, external controls appetite genitalia structure, secondary sexual Diabetes mellitus – much urine + sweetened characteristics, sexual behavior, ❖ Type 1 – occurs when too little insulin menstrual cycle is secreted from pancreas 2. Prostaglandins ❖ Type 2 – caused by insufficient no. of Mediate inflammatory responses insulin receptors Increase uterine contractions and Hyperglycemia – high blood glucose levels ovulations Polyphagia – increased appetite/eating OTHER HORMONES Polyuria – increased eating 1. Erythropoietin Polydipsia – excessive thirst Acts on bone marrow to increase the Gonads prod. of RBCs Gonads are organs that produce 2. Human chorionic gonadotropin (HCG) gametes and secretes sex hormones. Stimulated prod. of estrogen & Female: ovaries produce estrogen and progesterone progesterone Male: testes synthesize testosterone Estrogen and progesterone is responsible for development and function of the female reproductive organs and other female sexual characteristics Cyclical release of estrogen and progesterone regulates the menstrual cycle. These two hormones promote development of mammary glands and deposition of adipose tissue in breast, hips, and thighs during puberty. TESTES 1. Testosterone Aids in sperm cell prod. Maintenance of functional reproductive organs, secondary sexual characteristics, sexual behavior