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chapter 3 ...

4 Pages

Course Code
Psychology 1000
Derek Quinlan

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CHAPTER THREENeurons basic building blocks of the nervous system o Each neuron has 3 main parts Cell BodyDendritesAn Axon o Cell body or soma contains the biochemical structures needed to keep the neuron alive and its nucleus carries the genetic information that determines how the cell develops and functions Center to process and combine messages sent by neurons o Dendrites emerging from the cell body these are branchlike fibers They collect messages from neighboring neurons and send them on to the cell body o Axon conducts electrical impulses away from the cell body to other neurons muscles or glandsBloodbrain barrier prevents many substances including a wide range of toxins from entering the brainAction Potential or nerve impulse is a sudden reversal in the neurons membrane voltage during which the membrane voltage momentarily moves from 70 millivolts inside to 40 millivoltsDepolarization thisshift from negative to positiveGraded potentials when the dendrites or the cell body of a neuron are stimulated by axons from other neurons small shifts occur in the cell membranes electrical potential These changes are called graded potentials They are proportional to the amount of incoming stimulationAllornone law the action potential either occurs with maximum intensity or it does not occur at all Ion channels graded potentials change the membrane potential by acting on tiny protein structures in the cell membrane called ion channelsRefractory period time period during which the membrane is not excitable and cannot discharge another action potentialMyelin sheath tubelike fatty whitish insulation layer derived from glial cells during developmentSynapse a functional but not physical connection between a neuron and its target Synaptic cleft a tiny gap or space between the axon terminal of one neuron and the dendrite of the next neuronNeurotransmitters chemical substances that carry messages across the synapse to either excite other neurons or inhibit their firing produced by neuronsSynthesis stage chemical molecules are formed inside the neuronSynaptic vesicles chambers where molecules are storedReceptor sites large protein molecules embedded in the receiving neurons cell membrane Excitatory transmitters neurotransmitters that create depolarization
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