Endocrine System PDF
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Summary
This document provides an overview of the endocrine system, including the functions of different glands, hormones, and how they work together to regulate bodily functions. It explains various signaling mechanisms and how hormones interact with target cells.
Full Transcript
product to a body surface ENDOCRINE SYSTEM Internal Communication Endocrine Glands Nervous (axon) and endocrine (blood) systems facilitate Include the pituitary (anterior...
product to a body surface ENDOCRINE SYSTEM Internal Communication Endocrine Glands Nervous (axon) and endocrine (blood) systems facilitate Include the pituitary (anterior n posterior), thyroid, parathyroid, long-distance communication adrenal, and pineal glands Nervous system uses electrical signals Mainly secrete hormones ○ Neurotransmitters used for communication between one ○ Some have non-endocrine functions cell and another Do not have a duct for secretion Endocrine system uses hormones Secretions enter blood or interstitial fluid ○ Chemical signaling molecules that travel in blood Hormones affect target cells ○ Reach most cells of the body ○ Cells with receptors for that specific hormone ○ Have widespread effects Other Organs that Have Endocrine Function Functions of the Endocrine System Contains cells that have endocrine functions Helps maintain homeostasis by regulating: Includesthehypothalamus,thymus,heart,kidneys,stomach,small ○ Use of calories and nutrients intestine, liver, adipose tissue, ovaries, and testes ○ Secretion of wastes ○ Blood pressure and blood osmolarity Target Cells ○ Growth/Fertility and sex drive Receptor forcertainhormones ○ Lactation Hormones travel through the bloodstream ○ Sleep ○ They can reach almost any cell in the body Hormones only affect target cells Chemical Signalling ○ Cells with a receptor for a particular hormone Hormones:chemical messengers used by endocrine system Binding ofhormonetoreceptorontargetcellinitiatesintracellular ○ Most are released into blood signaling ○ Paracrine signaling: hormone affects neighboring cells (katabi) Nervous vs Endocrine System ○ Autocrine signaling: hormone affects same cell that Both nervous and endocrine systems allow control and released it (sarili) communication of the body ○ Endocrine signaling: hormone travels through blood to They accomplish this in different ways: affect cells throughout body (lahat w the help of bloof) ○ Neurotransmitters versus hormones Neurotransmitters-used by neurons and the nervous system ○ Nervous system is generally faster to make a change ○ Endocrine system has more widespread effects Endocrine and Exocrine Glands ○ Endocrine system effects generally last longer (unless Chemical secretions exit glands via exocytosis (lumalabas sa cell) ma-catalyze, they will ano their function) Endocrine gland secretion releases product into bloodstream or extracellular fluid Exocrine gland secretion releases product into duct that carries Hormones molecules Types of Hormones ○ Cannot be stored (no reserve) Based on chemical structure ○ Not soluble in blood ○ Steroid hormones-cross cell membrane easily Travel bound to transport proteins when in blood Lipid-based hormones Peptide hormones-translated like other proteins nonpolar ○ Modified and stored in vesicles until release (w reserve) always need carrier (protein) (lipoprotein) ○ Soluble in blood via LDL, HDL, VLDL Travel free" state ○ Amine-based hormones-modified amino acids Water-soluble; cannot cross cell membranes Hormone Receptors ○ Peptide and Protein hormones-made from chains of Receptors can be intracellular or on the cell surface amino acids Lipid-solublehormonereceptorsareusuallyintracellular(cytosolor Water-soluble; cannot cross cell membranes nuclear) ○ Thisisbecauselipid-solublehormonescanpassthrough Steroid Hormone cell membrane Produced from cholesterol molecules Water-soluble hormone receptors usually on surface of cell Lipid-soluble hormones ○ This is because these hormones are usually unable to ○ Can pass through cell membranes cross cell membrane Require transport proteins to travel in blood (carrier protein) (albumin is the most common carrier sa blood) Examples include testosterone and estrogens Amine Hormones Made from individual amino acids Water-soluble hormones ○ Cannot freely pass through the cell membrane Do not require transport proteins in blood Examples include melatonin, epinephrine and norepinephrine Peptide and Protein Hormones Chains of amino acids Intracellular Hormone Receptors Water-soluble hormones Associated with steroid and thyroid hormones (t3: watersoluble, ○ Cannot freely pass through the cell membrane t4: thyroglobular protein) Do not require transport proteins in blood ○ Hormone must be lipid-soluble to pass through Examples include antidiuretic hormone and insulin membrane May be in cytosol or nucleus Production of Hormones Results in increased transcription and increased protein synthesis Steroid hormones-made on demand by modifying cholesterol Membrane-bound Hormone Receptor Associated with water-soluble hormones Anatomy of Steroid Hormone ○ Amine and peptide hormones Steroid hormones are made on demand in endocrine cell Hormone serves as first messenger in the pathway ○ Enzymes modify cholesterol during synthesis ○ Anintracellularsecondmessengerrelaysmessageinside Secreted into blood and travel bound to a transport protein the cell Reach target cells where they are released from transport protein Bind to intracellular receptors within the target cell Second Messenger System 1. Hormone binds to receptor in cell membrane Anatomy of Protein Hormone 2. G protein is activated Protein hormones are made by rough ER or ribosomes in the 3. G protein activates adenylyl cyclase endocrine cell 4. Adenylyl cyclase converts ATP to cyclic adenosine Secreted into blood and travel in a "free" state monophosphate (cAMP) ○ Do not need transport proteins 5. CAMP activates protein kinases Reach target cells and bind to receptors on surface of cell 6. Protein kinases phosphorylate proteins ○ Initiate second messenger systems 7. Phosphorylated proteins cause change 8. Amplification allows a small amount of hormone to cause Factors affecting target cell response significant change Thenumberofreceptorsatargetcellhasinfluencesthestrengthof 9. Phosphodiesterase (PDE)breaks down cAMP response 10. Quickly stops internal cellular changes Downregulation-decrease in receptor number 11. Other second messenger systems may use calcium ions as a ○ Occurs when hormone level is chronically higher (T2 second messenger diabetes) bc the receptors are inhibited ○ Cells become less sensitive to hormone Upregulation-increase in receptor number ○ Occurs when hormone levels are chronically low (T1 diabetes) may receptors, pero wala insulin ○ Cells become more sensitive to hormone Regulation of Hormone Secretion Most hormones regulated via negative feedback loops ○ As hormone level rises, secretion will slow down or stop Oxytocin (love hormone) (hypothalamus produce but stored in posterior pituitary gland) is regulated by a positive feedback loop ○ Suckling, sex, and labor leads to oxytocin release ○ Higher levels of oxytocin will increase rate of release Other factors influence hormone release: A. Chemical levels within blood hypophyseal portal vein to the anterior pituitary Levels of nutrients or ions. Posterior pituitary contains nervous tissue B. Endocrine system-tropic hormones (master chief: ○ Axons from hypothalamus project through infundibulum hypothalamus) control release of other hormones Hormonesstoredandreleasedintobloodattheposterior C. Nervous system stimulation pituitary Posterior Pituitary Stores and releases two hormones ○ Oxytocin and antidiuretic hormone (ADH) ○ Hormonesareproducedinhypothalamusandtransported to posterior pituitary Oxytocin (for contractions in labor) ○ Release regulated by positive feedback loop ○ Responsible for milk ejection reflex (let down reflex) ○ Promotes uterine contractions ○ Contributes social bonding behavior Antidiuretic Hormone Released in response to high blood osmolarity ○ The solute concentration of blood (solvent is plasma) Conserves body fluids by increasing water reabsorption by kidney ○ Urine becomes darker Endocrine Control by the Hypothalamus and Pituitary Gland Can also cause constriction of blood vessels The Hypothalamus and the Pituitary Gland Leads to overall increase in blood pressure Hypothalamus: Release inhibited by drugs like alcohol Part of diencephalon of the brain ○ Higher amounts of urine produced ○ Regulates secretion of hormones from pituitary gland !! - alak inhibits antidiuretic hormone ○ Connected to posterior pituitary gland by infundibulum ○ Connected to anterior pituitary by Diabetes Insipidus hypothalamic-hypophyseal portal system (connects apg Results from chronic underproduction of anti-diuretic hormone and ppg) (ADH) ○ APG (8 hormones), PPG (2 hormones) Without ADH, kidneys do not reabsorb adequate amounts of water DI leads to excessive thirst and increased water consumption !! - ppg is from brain apg is from dila ○ Osmotic imbalance persists, however, due to lack of ADH lonic imbalances can occur in severe cases of D Anterior and Posterior Pituitary Gland primary:hormonedinagpproduce,secondary:receptors(totest: Anterior pituitary is composed of glandular tissue give artificial ADH) ○ Blood from hypothalamus travels through the natural; vasopressin, artificial; desmopressin ○ Increased lipolysis catabolic ○ Increased blood glucose levels catabolic Anterior Pituitary Gland Produces six hormones Growth Hormone Disorder ○ Secretion is regulated by tropic hormones from In general, growth hormone promotes growthofepiphysealplate hypothalamus during childhood growth hormone ○ Leads to elongation of bones thyroid stimulating hormone(t3t4)(tostimulate: Pituitary dwarfism need iodine) ○ Decreased stature due to decreased secretion of GH adrenocorticotropic hormone during childhood follicle-stimulating hormone Gigantism luteinizing hormone ○ Substantially increased height due to excessive GH prolactin secretion during childhood ○ Tropic hormones travel from hypothalamus to anterior Acromegaly pituitary in hypothalamic- hypophyseal portal system ○ Excessive GH secretion during adulthood ○ Causes increased growth of cartilage leading to larger Anterior Pituitary Hormones hands, feet, and ears. Growth hormone-anabolic (buildup) hormone that promotes ○ May cause cardiovascular complications due to protein synthesis and tissue building diabetogenic effect !! - cataabolic, breakdown !! - APG: production and secretion, PPG: secretion only hyroid-stimulating hormone-causes release of thyroid T Major Hormones of the Body hormones from thyroid gland (metabolism) The Thyroid Gland (1) Adrenocorticotropic hormone-stimulates release of cortisol Located anterior to trachea and inferior to larynx (stress hormone) from adrenal cortex Two lateral lobes connected by isthmus Follicle-stimulating hormone-promotes gamete production Histology: Luteinizing hormone-promotes release of sex hormones and ○ Thyroid follicles-spherical units of thyroid initiates ovulation Internal cavity filled with colloid Prolactin-promotes milk production Growth Hormone ReleaseregulatedbyGHRH(Growthhormoneregulatinghormone) and GHIH (somastostatin) from hypothalamus (stimulates liver)Causes production of insulin-like growth factors (IGFs) in target tissue Causes growth via: ○ Increased protein synthesis anabolic Calcitonin Synthesis and Release of Thyroid Hormone More sa children Thyroid hormone (TH) made by follicular cells Secreted and produced by parafollicular cells ○ Stimulated by TSH from anterior pituitary gland Secreted in response to elevated blood calcium levels Follicular cells bind iodine to thyroglobulin proteins in colloid Decreases blood calcium levels Intermediaries are combined to form T3 (triiodothyronine) and Ta ○ Inhibits osteoclast activity and stimulates osteoblast (tetraiodothyronine) activity ○ T4 commonly known as thyroxine, T3 is thyronine ○ Decreases calcium absorption by the intestine Hormones remain in colloid until needed ○ Increases calcium loss in urine TSH stimulates release of T3 and T₄ from follicular cells when necessary Calcium Regulation Calcium plays a role in many biological processes Regulation of Thyroid Hormone Synthesis Levels are regulated by hormones Negative feedback regulates TH secretion Calcitonin from thyroid and parathyroid hormone (PTH) from the Low levels of TH stimulate TRH.release from hypothalamus parathyroid glands work antagonistically to regulate calcium levels TRH stimulates release of TSH from anterior pituitary TSH stimulates release of TH from thyroid gland Parathyroid Glands (2) Located on posterior of thyroid gland Functions of Thyroid Hormones Oxyphil cell function is unknown Increase basal metabolic rate (BMR) Chief cells secrete parathyroid hormone (PTH) ○ Cause every cell to increase production of ATP ○ Secreted in response to low calcium levels Promote protein synthesis ○ Increases blood calcium levels Increase effectiveness of epinephrine and norepinephrine Stimulates osteoclasts that breakdown bone ○ Increase body temperature matrix releasing calcium Heat given off due to ATP production ○ Inhibits osteoblasts Required for adequate growth and development of skeletal and ○ Stimulates calcitriol production toincreaseabsorptionof nervous tissue in childhood dietary calcium Thyroid Disorders Goiterenlarged thyroid. ○ Caused by accumulation of colloid Hypothyroidism= insufficient production of thyroidhormones ○ May lead to weight gain and cold intolerance Hyperthyroidism= excessive production of thyroidhormones ○ May lead to weight loss and increased body temperature Parathyroid Disorders Main mineralocorticoid is aldosterone Hyperparathyroidism = excessive secretion of PTH leads to ○ Increases sodium and water reabsorption by kidney excessive bone resorption ○ Increases blood pressure Leads to increased blood levels of calcium resulting in: Involved in renin-angiotensin-aldosterone system (RAAS) ○ Decreased bone density, leading to increased fractures ○ Reduced responsiveness of nervous system The Hormones in Zona Fasciculata ○ Increased calcium deposits in tissues and organs Intermediate region of adrenal cortex Hypoparathyroidism= insufficient production or secretionof PTH Secretes glucocorticoids ○ Leads to low blood levels of calcium, causing muscle Main glucocorticoid is cortisol twitching, cramping, convulsions, or paralysis ○ Released in response to stress ○ Release stimulated by ACTH Adrenal Glands (3) ○ Suppresses immune system Triangular glands on top of each kidney ○ Stimulates breakdown of stored nutrients for energy Covered by capsule Glycogenolysis Divided into adrenal cortex (superficially) and medulla (deeper) Lipolysis Adrenal cortex has three zones: Gluconeogenesis 1. Zona glomerulosa 2. Zona fasciculata The Hormones in Zona Reticularis 3. Zona reticularis Deepest region of adrenal cortex Secretes androgens ○ These are male sex hormones Main androgen secreted is dehydroepiandrosterone (DHEA) Supplements testosterone in males Promotes libido in females The Adrenal Medulla Releases epinephrine and norepinephrine; collectively called catecholamines ○ Produced by chromaffin cells ○ Considered hormones when released into the blood Considered neurotransmitters at locations where they are released into a synapse Release results in fight-or-flight responses of the sympathetic nervous system The Hormones in Zona Glomerulosa Most superficial region of adrenal cortex Secretes mineralocorticoids