GN 012 Reizleitung / nerve impulse

Beschreibt die Reizleitung eines Axons - siehe Ton The membranes of all nerve cells have a potential difference across them, with the cell interior negative with respect to the exterior (a). In neurons, stimuli can alter this potential difference by opening sodium channels in the membrane. For example, neurotransmitters interact specifically with sodium channels (or gates). So sodium ions flow into the cell, reducing the voltage across the membrane. Once the potential difference reaches a threshold voltage, the reduced voltage causes hundreds of sodium gates in that region of the membrane to open briefly. Sodium ions flood into the cell, completely depolarizing the membrane (b). This opens more voltage-gated ion channels in the adjacent membrane, and so a wave of depolarization courses along the cell — the action potential. As the action potential nears its peak, the sodium gates close, and potassium gates open, allowing ions to flow out of the cell to restore the normal potential of the membrane

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