Chapter 6Cell-to-Cell Communication: OverviewSlide 3Slide 4Slide 5Slide 6Slide 7Long-Distance CommunicationSlide 9Slide 10CytokinesSignal transductionSlide 13Slide 14Signaling CascadesSlide 16Slide 17Chapter 6•Cell-to-cell communication•Signal pathways•Modulation of signal pathways© 2013 Pearson Education, Inc.Cell-to-Cell Communication: Overview•Physiological signals–Electrical signals–Changes in the membrane potential of a cell–Chemical signals–Secreted by cells into ECF–Responsible for most communication within the body•Target cells, or targets, respond to signals© 2013 Pearson Education, Inc.Four Basic Methods of Cell-to-Cell CommunicationLocal1. Gap junctions – direct transfer of electrical and chemical signals through protein channels 2. Contact-dependent – surface molecules on one cell membrane bind to surface molecules onanother3. ECF diffusion – chemicals released by one cell thatdiffuse to and act on anotherLong-Distance4.Nerves use a combination of electrical and chemicalsignals while circulating chemicals convey blood-borne messagesGap junctions formdirect cytoplasmicconnections betweenadjacent cells.Connexinscreate a protein channel (connexon),which is acytoplasmicbridge that allowsconnectedcells to actlike a singlecell = syncytiumConnexinsContact-dependent signalsrequire interaction betweenmembrane molecules ontwo cells.ContactReceptorAutocrine signals act on the same cellthat secreted them. Paracrine signalsare secreted by one cell and diffuse toadjacent cells.Autocrine v. ParacrineHormones are secreted by endocrine glands or cells into theblood. Only target cells with receptors for the hormone respondto the signal.BloodNo responseResponseTargetcellCellwithreceptorCellwithoutreceptorEndocrinecellHormonesLong-Distance Communication•The nervous system uses a combination of chemical and electrical signals for long distance cell-to-cell communication•Neurocrines are chemical signals secreted by neurons–Neurotransmitters–Neurohormones© 2013 Pearson Education, Inc.ElectricalsignalTargetcellResponseNeuronNeurotransmitters are chemicals secreted by neurons that diffuseacross a small gap to the target cell.Nervous SystemNeuronNeurohormones are chemicals released by neurons into the bloodfor action at distant targets.BloodResponseNo responseCellwithoutreceptorCellwithreceptorNeurohormonesCytokines•Cytokines may act as both local and long-distance signals•All nucleated cells synthesize and secrete cytokines in response to stimuli•In development and differentiation, cytokines usually function as autocrine or paracrine signals•In stress and inflammation, some cytokines may act on relatively distant targets© 2013 Pearson Education, Inc.Signal transductionBasic Signal TransductionFirstmessengerTransducerSecondmessengersystemTargetsSignalmoleculeMembranereceptor proteinIntracellularsignal moleculesTargetproteinsbinds toactivatesaltercreateResponseResponseIntracellular Signal ReceptorsReceptorin nucleusReceptor in cytosolLipophilic signalmolecules diffusethrough the cellmembrane.Binding tocytosolicor nuclearreceptorstriggersSlower responsesrelated to changesin gene activityIntracellularCell Membrane ReceptorsExtracellular signalmolecule binds to acell membrane receptor.BindingtriggersRapid cellularresponsesCell MembraneSignaling CascadesSignal transduction pathways form a cascade.SignalInactive AInactive BInactive CSubstrateConversion of substrateto product is the finalstep of the cascade.Active AActive BActive CProductSignal amplification allows a small amount ofsignal to have a large effect.LRAEReceptor-ligand complexactivates anamplifier enzyme (AE).One ligand is amplified into manyintracellular molecules.CellmembraneExtracellularFluidIntracellularFluidAmplificationCalcium As an Intracellular MessengerElectricalsignalExtracellularfluidIntracellularfluidVoltage-gatedCa2+ channelopens.Ca2+released fromintracellularCa2+ stores.Ca2+ in cytosolincreases.Ca2+Ca2+Ca2+ binds toproteins.Other Ca2+-binding proteins.ChemicalsignalAlters
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