NEURAL TRANSMISSION NEURAL TRANSMISSION Neurons Neurons Electrical and Chemical Electrical and Chemical Transmission Transmission
Feb 25, 2016
NEURAL TRANSMISSIONNEURAL TRANSMISSION
NeuronsNeuronsElectrical and Chemical TransmissionElectrical and Chemical Transmission
Neurons Neurons
NeuronsNeurons
Glial CellsGlial Cells
AstrocytesAstrocytes– Contact blood vessels and neuronsContact blood vessels and neurons– transport chemicals from blood to neuronstransport chemicals from blood to neuronsOligodendrocytesOligodendrocytes– Myelinate CNS axonsMyelinate CNS axonsSchwann cellsSchwann cells– Myelinate PNS axonsMyelinate PNS axons– Guide regeneration after damageGuide regeneration after damageRadial glia Radial glia – Guide neural migration during developmentGuide neural migration during development
CELL MEMBRANESCELL MEMBRANES
Membrane StructureMembrane Structure– Semipermeable lipid Semipermeable lipid
bilayerbilayer– ProteinsProteins
Ion channelsIon channelsTransport pumpsTransport pumpsReceptorsReceptors
MEMBRANE POTENTIALMEMBRANE POTENTIAL
MEMBRANE POTENTIALMEMBRANE POTENTIAL
Electrochemical Gradient Electrochemical Gradient – Electrostatic ForcesElectrostatic Forces
Electrical gradientElectrical gradientOpposite charges attract, Opposite charges attract, Same charges repelSame charges repel
– Diffusion ForcesDiffusion ForcesConcentration gradientConcentration gradient
RESTING MEMBRANE RESTING MEMBRANE POTENTIALPOTENTIAL
Diffusion ForcesDiffusion Forces– NaNa++ and Cl and Cl-- in in– KK++ out out
Electrostatic ForcesElectrostatic Forces– NaNa++ and K and K++ in in– ClCl-- out out
++
MEMBRANE POTENTIALMEMBRANE POTENTIAL
Na+/K+ PumpNa+/K+ Pump– Compensatory Compensatory
MechanismMechanism– Active when Active when
intracellular Na+ highintracellular Na+ high– Neutral or inactive Neutral or inactive
when intracellular Na+ when intracellular Na+ lowlow
ACTION POTENTIALACTION POTENTIAL
ACTION POTENTIALACTION POTENTIAL
CONDUCTION OF A.P.CONDUCTION OF A.P.
SYNAPTIC TRANSMISSION SYNAPTIC TRANSMISSION
NEUROCHEMICAL SYNAPSESNEUROCHEMICAL SYNAPSES
SYNAPTIC COMMUNICATIONSYNAPTIC COMMUNICATIONPOSTSYNAPTIC POSTSYNAPTIC POTENTIALSPOTENTIALS– Excitatory PSPExcitatory PSP– Inhibitory PSPInhibitory PSP
Electrical SynapsesElectrical Synapses– Gap junctionsGap junctions
Neurochemical Neurochemical SynapsesSynapses
Structures of Neurochemical SynapsesStructures of Neurochemical Synapses
Presynaptic Presynaptic MembraneMembranePostsynaptic Postsynaptic MembraneMembraneSynaptic VesiclesSynaptic VesiclesSynaptic CleftSynaptic CleftReceptor SitesReceptor Sites
Steps In Neurochemical TransmissionSteps In Neurochemical Transmission
SynthesisSynthesisStorageStorageNeurotransmitter ReleaseNeurotransmitter ReleaseReceptor ActivationReceptor ActivationNeurotransmitter DeactivationNeurotransmitter Deactivation– Enzymatic Deactivation (Metabolism)Enzymatic Deactivation (Metabolism)– ReuptakeReuptake
Steps in Neurochemical TransmissionSteps in Neurochemical Transmission
SYNTHESISSYNTHESIS
Receptor ActivationReceptor Activation
Ionotropic ReceptorsIonotropic Receptors– ligand gated ion channelsligand gated ion channels
Metabotropic ReceptorsMetabotropic Receptors– G proteinsG proteins– Second MessengersSecond Messengers
Neurotransmitter InactivationNeurotransmitter Inactivation Enzymatic Degradation (Metabolism)Enzymatic Degradation (Metabolism)
Acetylcholine is inactivated by an enzyme, Acetylcholine is inactivated by an enzyme, Acetylcholinesterase (AChE).Acetylcholinesterase (AChE).
The monoamines are inactivated by the The monoamines are inactivated by the enzyme, Monoamine Oxidase (MAO)enzyme, Monoamine Oxidase (MAO)
Catecholamines (DA, NE, E) are also Catecholamines (DA, NE, E) are also inactivated by and Catechol-O-inactivated by and Catechol-O-Methyltransferase (COMT).Methyltransferase (COMT).
ReuptakeReuptake The monoamines are also inactivated The monoamines are also inactivated
through reuptake.through reuptake.
MAJOR NEUROTRANSMITTERSMAJOR NEUROTRANSMITTERSAcetylcholineAcetylcholine MonoaminesMonoamines– CatecholaminesCatecholamines
EpinephrineEpinephrineNorepinephrineNorepinephrineDopamineDopamine
– IndoleaminesIndoleaminesSerotoninSerotonin
Amino Acid TransmittersAmino Acid Transmitters– Glutamate, AspartateGlutamate, Aspartate– GABA, GlycineGABA, GlycineNeuropeptidesNeuropeptides– EnkephalinsEnkephalins– EndorphinsEndorphins
Cholinergic PathwaysCholinergic Pathways
Dopaminergic PathwaysDopaminergic Pathways
Noradrenergic PathwaysNoradrenergic Pathways
Serotonergic PathwaysSerotonergic Pathways
Neurochemical PathwaysNeurochemical Pathways
DopamineDopamine– Nigrostriatal Pathways (Substantia Nigra Nigrostriatal Pathways (Substantia Nigra
Basal Ganglia)Basal Ganglia)– Mesolimbic, Mesocortical Patways (VTA Mesolimbic, Mesocortical Patways (VTA
NAc and pfCTX)NAc and pfCTX)– Most widely studied neurobiology theory of Most widely studied neurobiology theory of
drug dependence relates to dopaminedrug dependence relates to dopamine
Neurochemical PathwaysNeurochemical Pathways
AcetylcholineAcetylcholine– Pontine nucleiPontine nuclei
involved in components of REM sleepinvolved in components of REM sleep– Basal ForebrainBasal Forebrain
Reduced quantities found in Alzheimer’s patients Reduced quantities found in Alzheimer’s patients
NorepinephrineNorepinephrine– Locus Coeruleus Locus Coeruleus Forebrain Forebrain
Stimulant drugs may induce wakefulness through these Stimulant drugs may induce wakefulness through these pathwayspathways
Neurochemical PathwaysNeurochemical Pathways
Serotonin (5-HT)Serotonin (5-HT)– Raphe NucleiRaphe Nuclei– Research on weight control, aggressiveness, and Research on weight control, aggressiveness, and
depression are centered on 5-HTdepression are centered on 5-HTGABAGABA– Widespread in CNSWidespread in CNS– Related to seizures Related to seizures
EndorphinsEndorphins– Spinal cord and midbrainSpinal cord and midbrain– Involved in body’s natural mechanisms for pain reliefInvolved in body’s natural mechanisms for pain relief