Action Potentials
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What is the composition of extracellular and intracellular fluid? | show 🗑
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show | There are large proteins in the intracellular fluid that are negatively charged.
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What is the resting potential of the cell? | show 🗑
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show | Diffusion (molecules move from areas of high concentration to areas of low concentration) and electrostatic pressure (attraction and repulsion)
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Explain why potassium ions remain in the cell during resting potential. Assume that ions move freely | show 🗑
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Explain why Chloride ions remain in the cell during resting potential. Assume that ions move freely | show 🗑
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show | Diffusion pushes sodium in, and electrostatic pressure attracts sodium in as well.
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Although sodium is supposed to be attracted into the cell during rest, sodium concentration in the cell still is low. Why? | show 🗑
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During rest, what ion is allowed through by the membrane? | show 🗑
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The resting potential is supposed to be -93 mV. Why is it -70 mV instead? | show 🗑
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show | 1. Depolarization occurs: intra -5mV
2. Na+ enters cell: intra +40 mV.
3. K+ leaves near peak: intra is -charged
4. Na+ channels close at peak
5. Hyperpolarization: K+ channels close, Na+ channels gradually reopen, Na-K pumps pump Na+ out
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show | 1. Sodium channels open very rapidly, potassium channels open very slowly.
2. Sodium channels open only for a while, and reopen only when near resting potential. Potassium channels remain open for longer.
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What is the absolute refractory period? | show 🗑
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show | A period when a cell can only respond to larger than normal input. More depolarization is needed to reach firing threshold.
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What is all-or-none? | show 🗑
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show | Neural firing can vary to reflect stimulus intensity.
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show | When an action potential reproduces itself down the length of an axon from the axon hillock.
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show | It prevents action potentials from occurring in the previous length of axon. Thus, action potentials travel in one direction.
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show | 1. Sodium ions are moved by diffusion and electrostatic pressure to the adjacent axon segment.
2. Potassium ions in the segment are pushed by the sodium ions into the next axon segment.
3. Depolarization occurs. Threshold reached, firing commences.
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show | 1. Myelin prevents leakage of sodium ions as they move through axon -> fast travel
2. At nodes of Ranvier, another actionpotential is generated as concentration of ion channels is high.
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What is saltatory conduction? | show 🗑
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