Module 9: The Endocrine System PDF
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This document provides an overview of the endocrine system, including animal hormones, intercellular communication, and various signaling mechanisms such as endocrine, paracrine, and autocrine signaling. It also discusses the different classes of hormones and their effects.
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MODULE 9: THE ENDOCRINE SYSTEM aracrine & Autocrine Signaling: It involves local P regu...
MODULE 9: THE ENDOCRINE SYSTEM aracrine & Autocrine Signaling: It involves local P regulators. These are moleculesthatactovershort ANIMAL HORMONES distancesreaching target cells solely by diffusion. T hese are chemical signals that are secreted into thecirculatorysystemandcommunicateregulatory aracrine Signaling: Target cells lie near the P messages within the body. secreting cells. It can reach all parts of the body, but only target cells that have receptors for that hormone. It is controlled by the Endocrine system. T henervousandendocrinesystemoftenoverlapin utocrine Signaling: Target cell is also the A function. secreting cell. S ignaling of neurons influences the release of hormones. INTERCELLULAR COMMUNICATION As the way that signals are transmitted between othplaysrolesinprocessessuchasbloodpressure B animal cells. regulation, nervous system function, and reproduction. nimals use chemical signals to communicate in A diverse ways: L ocal regulators that mediate such signaling Endocrine Signaling include the prostaglandins. Paracrine and Autocrine Signaling Prostaglandins: These function in Synaptic & Neuroendocrine Signaling reproduction, the immune system, blood clotting, and pain response. ndocrine Signaling: Hormones secreted into E extracellular fluids by endocrine cells reach their Synaptic & Neuroendocrine Signaling: targetsvia the bloodstream. 1. Hormones will diffuse into and out of the ynaptic Signaling: Neurons form specialized S blood vessels. junctions with target cells calledsynapses. 2. Then it will bind to their target cells Neurotransmitters: Molecules secreted (determined by their receptors). byneuronsatsynapsesthatdiffuseshort distances and bind to receptors on ndocrine E signaling maintains homeostasis, target cells. mediatesresponsestostimuli,regulatesgrowth,and development. It also involves long distances between the endocrine cells and its target cells (since it can travel via the bloodstream). euroendocrine N Signaling: Specialized neurosecretory cells secrete molecules called neurohormonesthattraveltotargetcellsviathe bloodstream. 1 CELLULAR RESPONSE PATHWAYS T hey bind to receptorsinthecytoplasmornucleus of the target cells. ater-soluble Hormones: It is secreted by W exocytosis. It travels freely in the bloodstream and binds to cell-surface receptors. EXTRACELLULAR COMMUNICATION L ipid-soluble Hormones: It diffuses across cell membranes. Ittravelsinthebloodstreamboundto ignaling by Pheromones: Chemicals that are S transport proteins and diffuses through the releasedintotheenvironmentusedbymembersof membrane of target cells. an animal speciesto communicate. It serves many functions, including marking trails leading to food, defining territories, warning of predators, and attracting potential mates (Ex: Ants) CLASSES OF LOCAL REGULATORS L ocal Regulator: Prostaglandins are modified fatty acids. The others are polypeptides and some are gasses. itric Oxide (NO): Thisisagasthatfunctionsinthe N body as both a local regulator and neurotransmitter. When the levelofoxygeninbloodfalls,NO activates an enzyme that results in vasodilation, increasing blood flow to the tissues. CLASSES OF HORMONES T here are three major classes: (1)Polypeptides,(2) Steroids, and (3) Amines. Polypeptides & Amines:Both are water-soluble Polypeptides: Insulin Amines: NH2 chemical, Epinephrine pinephrine&Cortisolarenormallyforfight-or-flight. E Insulin is for when glucose levels are high. teroids: Also largely nonpolar hormones are S characterized as lipid-soluble. 2 MULTIPLE EFFECTS OF HORMONES xocrine Glands: These have ducts to carry E T he same hormone may have different effects on secreted substances onto body surfaces or into the target cells that have: body cavities. These include the salivary glands. Different receptors for the hormone Different signal transduction pathways IMPLE HORMONE PATHWAYS S Hormonesare: pinephrine: It increases blood flow to skeletal E Released from an endocrine cell muscles (beta-receptor). However, it decreases Travel through the bloodstream, and blood flow to the digestive tract (alpha-receptor). Interact with specific receptors within a target cell to cause a physiological response xample: The release of acidic contents of the E stomach into the duodenum stimulates endocrine cells there to secrete secretin. This causes target cells in the pancreas, a glandbehindthestomachtoraisethepHin the duodenum. ENDOCRINE TISSUES & ORGANS It utilizes a negative feedback loop as it inhibits a response by reducing the initial stimulus, thus preventing excessive pathway activity. ndocrineGlands:Theseareductlessorgans.These E include:thyroidandparathyroidglands,testes,and ovaries. 3 SIMPLE NEUROENDOCRINE PATHWAYS ENDOCRINE SYSTEM IN INVERTEBRATES S timulus is received by a sensory neuron, which stimulates a neurosecretory cell. rothoracicotropic Hormone (PTTH): It is produced P by neurosecretory cells in the larval brain. It also eurosecretory cell secretes a neurohormone, N controls the molting of larva. whichentersthebloodstreamandtravelstotarget cells. Intheprothoracicgland,PTTHdirectsthereleaseof ecdysteroid. xample: The Suckling of an infant stimulates E nervous signals that reach the hypothalamus. etamorphosis M Nerve impulses from hypothalamus trigger Bursts of ecdysteroid trigger each successive molt release of oxytocin from the pituitary gland. as well as metamorphosis. It causes mammary glands to secrete milk etamorphosis is not triggered until the level of M another hormone,Juvenile Hormone (JH), drops. NDOCRINE SYSTEM IN VERTEBRATES E The hypothalamus receives information from the nervous system and initiates responses throughthe endocrine system. It utilizesapositivefeedbackloopasitreinforcesa stimulus to produce an even greater response. In mammals, oxytocin causes the release of milk, causing greater suckling by offspring, which stimulates the release of more oxytocin. 4 ttached to the h A ypothalamus is the pituitary nterior Pituitary Hormones A gland, composed of the posterior pituitary and Thehypothalamuscontrolsthehormoneproduction anterior pituitary. in the anterior pituitary by releasing and inhibiting hormones. osterior Pituitary: This stores and secretes P hormones that are made in the hypothalamus. rolactin-releasing Hormone: It is from the P hypothalamusanditstimulatestheanteriorpituitary nterior Pituitary: This makes and releases A to secrete prolactin, which has a role in milk hormones under regulation of the production. hypothalamus. osterior Pituitary Hormones P Neurosecretorycellsofthehypothalamussynthesize Hormone Target the two posterior pituitary hormones. FSH & LH Testes, Ovaries ntidiuretic Hormone(ADH):Itregulatesphysiology A and behavior. It also increases water retention. It TSH Thyroid targets the Kidney tubules. ACTH Adrenal cortex xytocin: It regulates milk s ecretion b O y the mammary glands. It also regulates u terine Prolactin Mammary glands contraction during birthing. MSH Melanocytes GH Liver, bones, other tissues ENDOCRINE GLAND: HORMONES & FUNCTIONS ineal Gland P Melatonin: Participates in regulation of biological rhythms. 5 Hypothalamus drenal Gland A xytocin & Vasopressin: These are hormones O Adrenal Medulla: released from the posterior pituitary. pinephrine & Norepinephrine: Raises blood E eleasing&InhibitingHormones:Theseregulatethe R glucose level; increase metabolic activities, anterior pituitary. constrict certain blood vessels ituitary Gland P Adrenal Cortex: Anterior Pituitary: Glucocorticoids:Raise blood glucose level F ollicle-stimulating Hormone (FSH( & Luteinizing Hormone:Stimulates the ovaries & testes ineralocorticoids: Promote reabsorption of M Na+ and excretion of K+ in kidneys. T hyroid-stimulating Hormone (TSH): Stimulates the thyroid gland ancreas P Insulin:Lowers blood glucose level drenocorticotropic A Hormone (ACTH): Stimulates the adrenal cortex Glucagon:Raises blood glucose level Prolactin:Mammary Gland cells eproductive Organs R These hormones are found in both females and rowth Hormone (GH): Stimulates growth and G males, but with a major role in one sex. metabolic functions Ovaries: Posterior Pituitary: strogens: Stimulate uterine lining growth; E xytocin: Stimulates the contractionofsmooth O promote development and maintenance of muscle cells in uterus and mammary glands female secondary sex characteristics. asopressin/ Antidiuretic Hormone (ADH): V Progestins:Promote uterine lining growth Promotes retention of water by kidneys; influences social behavior and bonding Testes: Thyroid Gland ndrogens: Support sperm formation; promote A T hyroid Hormone(T3 &T4) :Stimulatesandmaintains development and maintenance of male metabolic processes secondary sex characteristics. Calcitonin:Lowers blood calcium level arathyroid Gland P Parathyroid Hormone (PTH): Raises blood calcium level 6 THYROID REGULATION: A HORMONE CASCADE 4: TSH stimulates endocrine cells in the thyroid # PATHWAY gland to secrete T3 and T4. #5:Thyroid hormone levels return to normal range. 6:ThyroidhormoneblocksTRHrelease,preventing # overproduction of thyroid hormone. PArATHYROID HORMONE & VITAMIN D: CONTROL OF BLOOD CALCIUM #1:Normal Blood Ca2+ Level (about 10 mg/100mL) #2:Blood Ca2+ level falls. #3:Parathyroid glands release PTH. 4: PTH stimulates Ca2+ release in bones (to #5). It # also stimulates Ca2+ uptake and promotes activation of vitamin D in kidneys (to #4.1). 4.1: Active vitamin D increases Ca2+ in # intestines. *Circulation throughout the body via blood. #5:Blood Ca2+ level rises (Back to 1). #1:Thyroid hormone levels drop. EVOLUTION OF HORMONE FUNCTION ver the course of evolution the functions of O 2:ThehypothalamussecretesThyrotropin-releasing # particular hormones havediverged. Hormone (TRH) into the blood. Portal vessels carry TRH to anterior pituitary. For example: Thyroid hormone playsaroleinmetabolism 3: TRH causes anterior pituitary to secrete # across many lineages. Thyroid-stimulating Hormone (TSH). Butinfrogs:itstimulatestheresorptionofthe tadpole tail during metamorphosis. 7
