PSY100Y5 Lecture : psych lec 3.docx
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PSY100Y5 Full Course Notes
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Axon: myelin insulates the nerve cell, speeds up conduction of nerve messages, terminal buttons of the axon release transmitter. The membrane of the neuron separates charges. The ions na+ and cl- are found outside the membrane, whereas the ion k+ is mostly inside the membrane. The membrane is slightly permeable to k+ ions, so at rest, inside is -70 millivolts relative to outside. At rest, few na+ ions are able to cross the membrane. Cross-section of nerve cell showing distribution of ions across the membrane. Graded potentials are generated at the dendrites and are conducted along the membrane to the axon hillock. If the summated activity at the axon hillock raises the membrane potential past threshold, an action potential (ap) will occur. During the ap, na+ ions flow into the cell raising the membrane potential to +40 mv, producing the spike. The restoration of the membrane potential to -70 mv is produced by an opening of channels to k+
