Nerve activates contraction

The Endocrine System

The Endocrine SystemUses chemical messages (hormones) that are released into the bloodHormones control several major processesReproductionGrowth and developmentMobilization of body defensesMaintenance of much of homeostasisRegulation of metabolismEffects Caused by HormonesSynthesis of proteins, such as enzymesActivation or inactivation of enzymesStimulation of mitosisMaintenance of body tempMaintain blood glucose levels

Hormonal Stimuli of Endocrine GlandsEndocrine glands are activated by other hormones

Figure 9.2aLocation of Major Endrocrine Organs

Figure 9.3Neural Stimuli of Endocrine GlandsNerve impulses stimulate hormone releaseMost are under control of the sympathetic nervous system

Figure 9.2cHormone TypesSteroid e.g. sex hormonesProtein e.g. ADHTyrosine e.g. thyroxineModes of actionPeptideBinds to receptor on membrane of target cellSecondary messenger activatedCauses change in cytoplasm

Modes of Action contSteroidHormone crosses membraneBinds to receptor in cytoplasmActivates geneProduces enzyme

Hypothalmus and PituitaryLocated at base of brainWork togetherHypothalmus is controlling partner

HypothalmusVascularizedMonitors many body functionsHas neurosecretory cellsReleases into portal vein that goes to Pituitary

PituitaryBelow hypothalmusAnterior and posterior lobesControlled by hypothalmusPosterior lobe is storage for hypothalmusNerve impulses cause release

Hormones of the Anterior Pituitary

Produces/Secretes Hormones

Controlled by hypothalmus

Inhibited by hypothalmus

Growth Hormone (GH)General metabolic hormoneMajor effects are directed to growth of skeletal muscles and long bonesCauses amino acids to be built into proteinsCauses fats to be broken down for a source of energyFunctions of Other Pituitary HormonesProlactin (PRL)Stimulates and maintains milk production following childbirthThyroid-stimulating hormone (TSH)Influences growth and activity of the thyroidOxytocinStimulates contractions of the uterus during laborCauses milk ejectionAntidiuretic hormone (ADH)Can inhibit urine productionIn large amounts, causes vasoconstriction leading to increased blood pressure (vasopressin)HomeostasisBody Temp = maintain temp by generating heat (metabolism, muscle contraction) and heat lose (skin)Benefits of maintaining body temp?Homeostasis contHeat sources: brain, heart, kidneys, skeletal muscle during activitySkin is site of heat lose

Homeostasis (Water Balance)Water levels are controlled in the kidneysCollecting ductsOsmoreceptors of hypothalmus monitor blood chemistryIf water levels low, causes decreased urine outputIf water levels high, causes increased urine output

Homeostasis (Water Balance)Hypothalmus triggers release posterior pituitary to release ADH (Anti-Diuretic Hormone)ADH enters blood stream, reaches collecting ductCauses permeability of collecting ductWater leaves duct and returns to bodyIf water levels increase, osmoreceptors trigger stoppage of ADH releaseNo ADH in collecting ducts causes them to be impermeableWater goes to bladder

SkinWhen body is warmVasodialationRelaxation of hair erector musclesSweat productionWhen body is coldVasoconstrictionContraction of hair erector musclesSweat not producedThyroid GlandFound at the base of the throatProduces two hormonesThyroid hormoneCalcitonin

Thyroid HormoneMajor metabolic hormoneComposed of two active iodine-containing hormonesThyroxine (T4) secreted by thyroid folliclesTriiodothyronine (T3) conversion of T4 at target tissuesCalcitoninDecreases blood calcium levels by causing its deposition on bone

Parathyroid GlandsTiny masses on the posterior of the thyroidSecrete parathyroid hormoneStimulate osterclasts to remove calcium from boneStimulate the kidneys and intestine to absorb more calciumRaise calcium levels in the blood

Slide 9.27Adrenal GlandsCopyright 2003 Pearson Education, Inc. publishing as Benjamin CummingsTwo glandsCortex outer glandular region in three layersMedulla inner neural tissue regionSits on top of the kidneys

Hormones of the Adrenal GlandsSex hormonesProduces two similar hormones catecholaminesEpinephrineNorepinephrineThese hormones prepare the body to deal with short-term stressDiabetesType I early onsetNo insulin produced in B cellsUsually autoimmune or mutationSymptomsThirstExcess urinationTreatmentInjectionsmedications

Type II late onsetFailure of insulin receptors on target cellsCommon in overweightSymptomsGlucose fluctuationsTreatmentDietmedicationsSlide 9.32aPancreatic IsletsCopyright 2003 Pearson Education, Inc. publishing as Benjamin CummingsThe pancreas is a mixed glandThe islets of the pancreas produce hormonesInsulin allows glucose to cross plasma membranes into cells from beta cellsGlucagon allows glucose to enter the blood from alpha cellsThese hormones are antagonists that maintain blood sugar homeostasisSlide 9.32bPancreatic IsletsCopyright 2003 Pearson Education, Inc. publishing as Benjamin Cummings

Figure 9.13Regulation of Blood GlucoseAvg level in blood glucose is 90mg/100cm3Body tries to maintain thisLow glucose is called hypoglycemiaHigh glucose is called hyperglycemia (leads to dehydration)Mechanism of glucose regulationGlucose stored in liver as glycogenGlucose detected by islets of langerhans (in pancreas)B cells stimulated, secrete insulinStimulates uptake of glusose into cellsIncreases rate glucose is usedTriggers glycogenesisIncreases conversion into fatMechanism of glucose regulation contWhen glucose levels decrease islets shut-offA cells trigger glucogon production Causes conversion of glycogen to glucoseSlide 9.34Pineal GlandCopyright 2003 Pearson Education, Inc. publishing as Benjamin CummingsFound on the third ventricle of the brainSecretes melatoninHelps establish the bodys wake and sleep cyclesMay have other as-yet-unsubstantiated functions

Slide 9.35ThymusCopyright 2003 Pearson Education, Inc. publishing as Benjamin CummingsLargest in infants and childrenProduces thymosinMatures some types of white blood cellsImportant in developing the immune system

Slide 9.36Hormones of the OvariesCopyright 2003 Pearson Education, Inc. publishing as Benjamin CummingsEstrogensStimulates the development of secondary female characteristics Matures female reproductive organsHelps prepare the uterus to receive a fertilized eggPrepares the breasts to produce milkProgesterone

Hormones of the OvariesActs with estrogen to bring about the menstrual cycleHelps in the implantation of an embryo in the uterus

Hormones of the TestesProduce several androgens Testosterone is the most important androgenResponsible for adult male secondary sex characteristicsPromotes growth and maturation of male reproductive systemRequired for sperm cell production

Slide 9.39Other Hormone-Producing Tissues and OrgansCopyright 2003 Pearson Education, Inc. publishing as Benjamin CummingsParts of the small intestineParts of the stomachKidneysHeartMany other areas have scattered endocrine cells