How Do Neurons Work?Neurons and SynapsesSensory NeuronsMotor NeuronsInterneuronsStructures of a neuronThe cell bodyDendritesAxonMyelin sheathHow neurons communicateNeuron to NeuronSynapseNeurotransmitter ReleaseLocks and KeysSome Drugs work on receptorsSummary of Terms Do you know them?How Do Neurons Work?2Neurons and SynapsesTypes of NeuronsSensory MotorInterneurons3SpinalCordBrainSensoryNeuronSensory NeuronsINPUT From sensory organs to the brain and spinal cord.Drawing shows a somatosensory neuronVision, hearing, taste and smell nerves are cranial, not spinal4SpinalCordBrainSensoryNeuronMotorNeuronMotor NeuronsOUTPUT From the brain and spinal cord To the muscles and glands.5SpinalCordBrainSensoryNeuronMotorNeuronInterneuronsInterneurons carry information between other neurons only found in the brain and spinal cord.6Structures of a neuron7The cell bodyRound, centrally located structure Contains DNAContains the cell’s Nucleus8DendritesInformation collectorsReceive inputs from neighboring neuronsInputs may number in thousandsIf enough inputs the cell’s AXON may generate an output9AxonThe cell’s output structureOne axon per cell, 2 distinct partstubelike structure branches at end that connect to dendrites of other cells10Myelin sheathWhite fatty casing on axon Acts as an electrical insulator When present increases the speed of neural signals down the axon.Myelin Sheath11How neurons communicateNeurons communicate by means of an electrical signal called the Action PotentialAction Potentials are based on movements of ions between the outside and inside of the cellWhen an Action Potential occurs a molecular message is sent to neighboring neurons12Neuron to NeuronAxons branch out and end near dendrites of neighboring cellsAxon terminals are the tips of the axon’s branchesA gap separates the axon terminals from dendritesGap is the SynapseCellBodyDendriteAxon13Synapseaxon terminals contain small storage sacs called synaptic vesiclesvesicles contain neurotransmitter moleculesSendingNeuronSynapseAxonTerminal14Neurotransmitter ReleaseAction Potential causes vesicle to openNeurotransmitter released into synapseLocks onto receptor molecule in postsynaptic membrane15Locks and KeysNeurotransmitter molecules have specific shapespositive ions (NA+ ) depolarize the neuron negative ions (CL-) hyperpolarizeWhen NT binds to receptor, ions enterReceptor molecules have binding sites16Some Drugs work on receptorsSome drugs are shaped like neurotransmittersAntagonists : fit the receptor but poorly and block the NTe.g. beta blockersAgonists : fit receptor well and act like the NTe.g. nicotine.17Summary of Terms Do you know them?•3 types of neurons•Ion movements•Action potentials•Synapse•Neurotransmitters•Receptors and ions•Agonists and
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