Describe the structure of a voltagegated sodium ion channel

Describe the structure of a voltage-gated sodium ion channel

Describe the function of the voltage-gate sodium ion channel. In your description, explain what is meant by channel gating and channel inactivation.

Solution

Voltage gated channels

Voltage gated channels are those gated channels that open in response to voltage stimulus or a change in the membrane potential. These are located in the axons of all type of neurons. These channels participate in the generation of action potentials and also their conduction in the axons of all types of neurons.

The inflow of sodium ions causes the occurrence of depolarisation phase and when there is outflow of potassium ions, there is a repolarizing phase of an action potential. The changes in the ion flow can be described as follows:

1. Resting state

Initially, all the voltage gated channels remain close. The axon plasma membrane is said to be at resting membrane potential. There is a small negative charge along the inner surface of the membrane and subsequently a small positive charge along the outer surface of the membrane.

2. Depolarisation phase

The sodium channel activation gates open as the membrane potential of the axon reaches threshold. Here, the membrane depolarises as the sodium ions move into the neurons through these channels and there is a buildup of positive charges along the inner channel of the membrane.

3. Repolarization phase begins

Potassium channels open and the sodium channel inactivation gates close. At this point the membrane repolarisation begins with the exit of the potassium ons from the neurons. This leads to the buildup of negative ions along the inner surface of the membrane.

4. Repolarization phase continues

The outflow of potassium ions continue to happen here . There is an increase in the negative charges on the inner surface of the membrane with the continued exit of potassium ions from the neuron. The resting membrane potential is eventually restored as the outflow of potassium ions continue. Sodium ions channel inactivation gates finally open with the closure of the activation gates. Resting state is returned with the closure of potassium gates.

Gating is defined as the opening or closing of them ion channels. They are said to be non conducting channels. When in a closed state the channels are impermeable as no electrical currents will be allowed to pass through them.