Re: Why does the brain need electricity to operate? Does it?

Hi,

As a matter of fact you should rather say that the brain generates electricity when it is at work. But let me start with the basics assuming that you haven't had a lot of exposure to neurophysiology until now (I am very unfamiliar with the school curriculum in the US since I grew up in Germany).

The brain itself, as you probably know, consists of billions of cells, each of them possessing a plasma membrane.

This plasma membrane is a very effective, though not perfect, barrier to the passage of charged particles, either ions such as sodium, potassium, and chloride, or larger molecules such as amino acids and proteins of various sizes. Imagine the plasma membrane to be somewhat like the blobs of grease on chicken broth. The watery part of the broth would then be the intracellular fluid. Now imagine that you also had watery broth on top of the grease. The grease would then separate both watery (scientists say: aqueous) phases being a sort of 'lipid' (=fatty) membrane. In addition, the plasma membrane also contains protein molecules that either stretch through the membrane or are more or less loosely associated with it. One class of proteins are the ion channels which let ions pass through the membrane.

Since the charged particles are separated by a membrane and the concentrations of these ions are different on either side of the membrane the cells in effect generate an electric field across the membrane with a certain voltage (also called the resting membrane potential - you might have heard this term before) just like the field being built up by a battery. In most cells this resting membrane potential is somewhere around -50 to -80 mV (milliVolts). This means that the inside of the cell is negative with reference to the outside of the cell. Or in other words: the positive pole of the battery is on the outside and the negative pole on the inside. You can find a pretty decent not overly complicated introduction to the basic neurophysiology of nerve cells in David Atkins' tutorial. (Don't bother with the equations in the lower part of the page.)

The electric field thus generated creates a force that has the ability to drive ions across the membrane just like a battery drives electrons through an electrical circuit thereby causing an electrical current.
In the resting state, though, comparatively few ions pass through the membrane because the ion channels in the membrane are pretty much 'closed'.

This changes when a signal from an adjacent cell reaches the target cell. At the synapse, e.g. on the dendrites, specific signaling molecules, so called neurotransmitters, bind to channel molecules, and 'unlock' them (To be more correct, there are also channels that close after such a signal - but for simplicity's sake I'll omit this case). Small ions, i.e. potassium, chloride, magnesium, and sodium (the amino acids and proteins are usually to large to fit through the selective channels) can now pass through the channels and do so in accordance with the 'outside' electric field and, in addition, along their individual concentration gradients, i.e. from areas of higher to areas of lower concentrations. This results in changes of the membrane voltage - it either becomes more positive (depolarization), more negative (hyperpolarization), or stays the same (think of that as a depolarization and a hyperpolarization happening at the same time).
Note, though, that channels can also open in response to a change in the membrane voltage itself. This is what happens at the axon hillock (initial segment) and along the axon during an action potential. But I won't go into detail here.

To put it all in a nutshell: the neurons (=nerve cells) generate electricity and electrical currents (=flow of ions) by:
a) keeping charges separated in the resting state - the ions have different, more or less stable, concentrations inside and outside the cell (this is because they cannot pass freely through the membrane).
b) 'shifting around' ions through channels once a signal reaches the cell. The channels can be opened/unlocked either by neurotransmitters that bind to them or by the changing electric field itself.
To be receptive to a new signal the ion distribution has to be returned to its original state which is done by a sodium potassium pump which pumps out excess sodium and transports potassium back into the cell.

Now you may ask yourself where the energy comes from to run the whole process. The energy is generated by burning food stuff, which in the brain predominantly are sugars. These sugars are used to produce ATP (adenosine triphosphate), a chemical substance which stores energy in an easily accessible form. The energy contained in ATP is then used to drive all kinds of processes, e.g. the sodium-potassium-pump which is one of the main consumers of energy in your brain.

References:

• Elec tron micrographs of the plasma membrane. Don't bother with the scientific background too much if you don't understand it right away. Just enjoy some of the images.
• The membrane potential
• Some simulations of processes at the cell membrane.