Introduction to Neurophysiology

Original Editor - Joanne Garvey.

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Ion Channels

• An ion channel is a protien macromolecule that crosses the breadth of a membrane and allows molecules to pass through. The ions move in a direction determined by the electrochemical gradient across the membrane.
• Ions tend to flw from an area of high concentration to an area of low concentration.
• In the presence of a voltage gradient, there may be no flow of ions depite unequal concentrations.
• Ion channels can be open or closed.
• Opening is brought about by changing the voltage across the membrane, or binding a chemical substance to a receptor.
• Most important role is that they provide the neuron with electrical excitability.
• Found in all parts of the neuron and to a lesser extent in the neuroglial cells.

Types of channel

1. Voltage gated
2. Chemically Activated
3. Mechanical stretch/pressure.

Fundamental properties of an Ion Channel.

1. It is made up of a number of protien sub units, sitting across the membrane, allowing ions to cross from one side to the other. (Transmembrane pore)
2. The channel must be able to move from open to closed state, and back.
3. Must be able to open in response to the appropriate stimuli.

Some channels respond to chemical stimulus (particularly at the synapse). These channels have specific receptors for that chemical, that leads to channel opening.

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References

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