I keep hearing that there's always electrical activity taking place inside the human brain. Our heart and various other organs function because it receives electrical signals called impulse. But, what's the "voltage source" for the brain? How does it receive signals? Does it generate on it's own? If so, how?
[Physics] What’s the source of electricity for the human brain
biophysicselectricity
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The human body produces a wide range of bioelectromagnetic signals from various electrical impulses in the brain. The origin of the magnetic field is the charge exchange in the muscular and neural tissues (i.e no magnetic material is usually present in the body with very rare exceptions).
The brain's magnetic field varies from 10s of fT to 100s of fT [1]. The frequency varies from 0.1 Hz to <100 Hz. Measurement of brain magnetism is limited by the complexity of signal due to the overlap of the signals from various parts of the brain. In magentoencephelograpahy this is done using SQUIDS [2].
The second part of your question is about magnetic excitement of brain functions. This is in fact possible and some testing/use is reported with limited clinical success. The strength of the applied magnetic fields are 1-5T for trans-cranial excitation [3].
[1] http://www.bem.fi/book/12/12.htm#02 [2] http://www.scholarpedia.org/article/Magnetoencephalogram [3] http://en.wikipedia.org/wiki/Transcranial_magnetic_stimulation [4] http://www.bem.fi/book/22/22.htm An excellent source for this topic is [1]
These are all good questions! Based on your description I assume you haven't had an introduction to solid state physics yet? Let's take your image of an electron that "jumps"
from atom to atom. In my understanding I wouln't describe it that way, to me it's a wavefunction of the electron that is almost independent from the valence electrons and you
can use the free electron gas approximation. Why is this band independent? See the following picture for an intuitive understanding how the atomic potentials define the possible energy levels within a periodic arrangement of atoms:
I think most of your questions will be easier to answer if you make yourself familiar with basic concepts and approximations people use to describe electrons in a solid first. Sure, a lot of things can be understood if we consider electrons to be little spheres that scatter from bigger spheres (ions), but you said you want to understand on the atomic level -> it's good to see the electron as a wave and see how this wave behaves in a lattice with certain boundary conditions.
First, I would read about a crystal. Atoms are arranged in a periodic lattice (assume a nice crystal for a first simple picture) and you can make assumptions based on this periodicity. You can define a unit cell and the Brillouin zone. You will see that the energy levels will sometimes split up in different bands and based on the filling of these bands you end up wih a metal, insulator etc. Electrons are fermions, can two electrons be in the same state? This defines the Fermi velocity.
This filling of the available energy levels describes the Fermi surface, a very useful tool to describe other more advanced concepts. Then you will see what happens if you change the arrangements of the atoms or why in different spatial directions electrons can move due to the bonding of different atomic orbitals.
This could be a good start ; ) -> http://britneyspears.ac/lasers.htm
There are other introductions out there, most of them describe the basics really well.
Best Answer
These voltages are generally the result of small channels in cell membranes that swap charged ions back and forth such that an electrical potential is created. This can happen with Na+, Ca2+, and others. The basic idea is that if you bring +1 of charge in one direction and push +2 in the other direction, you've generated a charge.
That static charge then depolarizes neighboring channels, causing them to make the same swap, and so on, in a chain-reaction.
It's a little more complex than that :-) but that'll get you started.
https://secure.wikimedia.org/wikipedia/en/wiki/Action_potential