How Electrodes in salt solution can increase the electric potential

[Lucid Dreamer]

Hello,

I'm not sure if this is the right place for this question, but I am trying to understand how placing electrodes in the brain elicits action potentials.

In a neuron (brain cell), there exists a solution of sodium and potassium ions (among other things). When the brain wants to produce an action potential (electrical spike), the neuron brings in a lot of sodium ions from the outside to make the neuron more positive. It is this positive depolarization that starts an action potential. To artificially simulate this process, we place electrodes on the neuron. My question is how is an electrode able to increase the potential? From what I understand, electrodes can only supply a current of electrons (negatively charged).

EDIT: A lot of papers refer to "injecting current in a cell." I don't understand what that means as you would need an acceptor of electorons within the cell (or a donor)

 

[Borek]

Don't they connect battery to the electrodes?

 

[Lucid Dreamer]

Yeah, it's usually connected to a DC source or battery. But my questions has more to do with the actual mechanism of how electrons in the electrodes can be used to positively or negatively polarize a salt solution

 

[Borek]

Potential difference means there is an electric field present, doesn't matter what is its source.

 

[LudusRex]

to have current, right?

Great question! Let's break it down step by step.

First, it's important to understand that the movement of ions (such as sodium and potassium) is what creates the electrical potential in a neuron. This is known as the resting membrane potential. In a resting neuron, there is a higher concentration of positively charged ions outside the cell and a higher concentration of negatively charged ions inside the cell. This creates a difference in electrical charge, also known as the electric potential.

Now, when a neuron receives a signal, it opens ion channels that allow these ions to flow in and out of the cell, causing a change in the electric potential. This change in potential is what we call an action potential.

So, how do electrodes come into play? When we place electrodes on the neuron, we are essentially creating an external source of electrical potential. By applying a current through the electrodes, we can manipulate the movement of ions in the neuron. This can either increase or decrease the electric potential, depending on the direction of the current.

To answer your question about injecting current into a cell, it is important to note that cells have channels that allow for the flow of ions. This means that they can also act as conductors for electrical current. By injecting a current through the electrodes, we are essentially using the cell as a pathway for the current to flow. This can then affect the movement of ions and ultimately change the electric potential of the cell.

In summary, electrodes in salt solution can increase the electric potential by manipulating the movement of ions in a neuron through the application of a current. This allows for the artificial generation of action potentials, which can be useful in studying the function of neurons and their role in various processes in the brain. I hope this helps clarify things for you!