Action Potentials Read this: The sodium and potassium gates in the nerve cell ax

Question

Action Potentials Read this: The sodium and potassium gates in the nerve cell axon are voltage-gate means they open and close in response to changes in transmembrane potential. When the nerve cell is depolarized to -55mV at the When the cell reaches threshold, many sodium gates on the axon open. These open due to changes in transmembrane potential; they are voltage-gated. Whe gates open, sodium rushes into the cell. d. This trigger zone, it has reached threshold. sodium gates 1) What effect will the opening of many sodium gates have on transmembrane potential? a. Depolarization-the transmembrane potential will become less negative b. Hyperpolarization- the transmembrane potential will become more negative Imagine that many voltage-gated sodium gates open and many, many sodium ions rush into the axon of the cell. The charge on the axon near the trigger zone is now +35 mV. Is the inside of the cell now more positive or more negative than the outside? By the time the cell reaches +35 mV, the change in transmembrane potential has caused the potassium gates to open. Consider the potassium ions inside the cell. Consider the chemical and electrical gradients 3) Where is the chemical concentration of potassium higher? Inside the cell Outside of the cell a. b. 4) Based on the chemical gradient, which way would you expect potassium to move? a. into the cell b. Out of the cell The part of the axon near the trigger zone is now +35 mV (positive inside). Based on the electrical gradient, which way would you expect potassium to move? 5) Into the cell Out of the cell a. b. If a cell has a charge of +35 mV and many potassium ions leave the cell, which of the following is a possible charge on the cell? 6) a. +35 mV b. +25 mV c. +45 mV

Explanation / Answer

1) Voltage gated ion channel opens when there is a shift in membrane potential past the threshold value. When nerve cells reach the threshold it will cause to open sodium channels & influx of sodium ions. A typical neuron has a resting potential of -70 mV & threshold potential about -55 mV. As the sodium is cation, so opening of many sodium gates will cause influx of large quantity of cations. This will result in the depolarization of membrane potential- the trans-membrane potential will become less negative. So, the correct answer will be option a.

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