Lecture 4 - Lecture 4 Anatomy of neuron The language of...

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Lecture 4 Anatomy of neuron The language of Neurons: The Action Potential: Electrochemical impulse that travels at a constant strength Either excitatory (yes) or inhibitory (no) All-or-none law Resting potential- the neuron is at rest (no action potential Axon Schematic Outside the axon: More sodium (Na+) More positive charge Inside the axon: More potassium (K+) More negative charge (due to chloride and proteins) Sodium ions attract protein ions (opposites attract) AP is caused by an exchange of ions across the neuron membrane Na channels open. Na ions rush into the neuron. The neuron becomes more positive and thus depolarized K channels also open K rushes out of the cell, reversing the depolarization At about this time, Na channels start to close Gradually, the ion concentrations go back to resting levels (resting potential) Chronology of the Action Potential 1) Na+ gates open 2) Inside of axon becomes more positively charged 3) If the inside becomes sufficiently positively charged (crossing the threshold of excitation) more Na+ gates open producing the action potential 4) Positively charged action potential travels down the axons causing Na+ gates to open allowing more positive charge to enter the axon at each point along the way, thereby perpetuating the action potential 5) Behind the action potential, Na+ gates close and K+ gates open, allowing K+ to exit
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