Copyright © 2005 Pearson Education, Inc. publishing as Benjamin CummingsOverview: The Body’s Long-Distance Regulators• Animal hormones are chemical signals that aresecreted into the circulatory system andcommunicate regulatory messages within the body• Hormones reach all parts of the body, but onlytarget cells are equipped to respondCopyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings• Insect metamorphosis is regulated by hormonesCopyright © 2005 Pearson Education, Inc. publishing as Benjamin CummingsCopyright © 2005 Pearson Education, Inc. publishing as Benjamin CummingsConcept 45.1: The endocrine system and the nervous systemact individually and together in regulating an animal’sphysiology• Animals have two systems of internalcommunication and regulation: the nervoussystem and the endocrine systemCopyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings• The nervous system conveys high-speed electricalsignals along specialized cells called neurons• The endocrine system secretes hormones thatcoordinate slower but longer-acting responsesCopyright © 2005 Pearson Education, Inc. publishing as Benjamin CummingsOverlap Between Endocrine and NervousRegulation• The endocrine and nervous systems functiontogether in maintaining homeostasis,development, and reproduction• Specialized nerve cells known as neurosecretorycells release neurohormones into the blood• Both endocrine hormones and neurohormonesfunction as long-distance regulators of manyphysiological processesCopyright © 2005 Pearson Education, Inc. publishing as Benjamin CummingsControl Pathways and Feedback Loops• There are three types of hormonal controlpathways: simple endocrine, simpleneurohormone, and simple neuroendocrine• A common feature is a feedback loop connectingthe response to the initial stimulus• Negative feedback regulates many hormonalpathways involved in homeostasisLE 45-2aTargeteffectorsResponseSimple endocrine pathwayGlycogenbreakdown,glucose releaseinto bloodLiverBloodvesselPancreassecretesglucagon ( )EndocrinecellLow bloodglucoseReceptorproteinStimulusPathwayExampleLE 45-2bTargeteffectorsResponseSimple neurohormone pathwayStimulusPathwayExampleSucklingMilk releaseSmooth musclein breastNeurosecretorycellBloodvesselPosterior pituitarysecretes oxytocin( )Hypothalamus/posterior pituitarySensoryneuronLE 45-2cTargeteffectorsResponseSimple neuroendocrine pathwayStimulusPathwayExampleMilk productionBloodvesselHypothalamusSensoryneuronMammary glandsEndocrinecellBloodvesselAnteriorpituitarysecretesprolactin ( )Hypothalamussecretes prolactin-releasinghormone ( )NeurosecretorycellHypothalamicneurohormonereleased inresponse to neural andhormonalsignalsCopyright © 2005 Pearson Education, Inc. publishing as Benjamin CummingsConcept 45.2: Hormones and other chemical signals bind totarget cell receptors, initiating pathways that culminate inspecific cell responses• Hormones convey information via the bloodstreamto target cells throughout the body• Three major classes of molecules function ashormones in vertebrates:– Proteins and peptides– Amines derived from amino acids– SteroidsCopyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings• Signaling by any of these hormones involves threekey events:– Reception– Signal transduction– ResponseCopyright © 2005 Pearson Education, Inc. publishing as Benjamin CummingsCell-Surface Receptors for Water-SolubleHormones• The receptors for most water-soluble hormonesare embedded in the plasma membrane,projecting outward from the cell surfaceLE 45-3SECRETORYCELLHormonemoleculeSignal receptorVIABLOODVIABLOODTARGETCELLTARGETCELLSignaltransductionpathwayORCytoplasmicresponseDNANUCLEUSNuclearresponseReceptor in plasma membrane Receptor in cell nucleusDNANUCLEUSmRNASynthesis ofspecific proteinsSignaltransductionand responseSignalreceptorHormonemoleculeSECRETORYCELLCopyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings• Binding of a hormone to its receptor initiates asignal transduction pathway leading to responsesin the cytoplasm or a change in gene expression• The same hormone may have different effects ontarget cells that have– Different receptors for the hormone– Different signal transduction pathways– Different proteins for carrying out the responseCopyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings• The hormone epinephrine has multiple effects inmediating the body’s response to short-term stressLE 45-4Different receptorsdifferent cell responsesEpinephrineα receptorEpinephrineβ receptorEpinephrineβ receptorVesselconstrictsVesseldilatesIntestinal bloodvesselSkeletal muscleblood vesselLiver cellDifferent intracellular proteins different cell responsesGlycogendepositsGlycogenbreaks downand glucoseis releasedfrom cellCopyright © 2005 Pearson Education, Inc. publishing as Benjamin CummingsIntracellular Receptors for Lipid-Soluble Hormones• Steroids, thyroid hormones, and the hormonalform of vitamin D enter target cells and bind toprotein receptors in the cytoplasm or nucleus• Protein-receptor complexes then act astranscription factors in the nucleus, regulatingtranscription of specific genesCopyright © 2005 Pearson Education, Inc. publishing as Benjamin CummingsParacrine Signaling by Local Regulators• In paracrine signaling, nonhormonal chemicalsignals called local regulators elicit responses innearby target cells• Types of local regulators:– Neurotransmitters– Cytokines and growth factors– Nitric oxide– ProstaglandinsCopyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings• Prostaglandins help regulate aggregation ofplatelets, an early step in formation of blood clotsCopyright © 2005 Pearson Education, Inc. publishing as Benjamin CummingsCopyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings• The hypothalamus and the pituitary gland controlmuch of the endocrine systemConcept 45.3: The hypothalamus and pituitary integratemany functions of the vertebrate endocrine systemCopyright © 2005 Pearson Education, Inc. publishing as Benjamin CummingsCopyright © 2005 Pearson Education, Inc. publishing as Benjamin CummingsLE 45-6Testis(male)Ovary(female)Adrenal glandsPancreasParathyroid glandsThyroid glandPituitary glandPineal glandHypothalamusCopyright © 2005 Pearson Education, Inc. publishing as Benjamin CummingsRelation Between the Hypothalamus and PituitaryGland• The
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