Electroencephalography (EEG) is based on synaptic currents

http://www.brightmindsinstitute.com/blog/

http://quizlet.com/4239544/cog-sci-chapter-2-flash-cards/http://www.acm.org/conferences/sac/sac2000/Proceed/FinalPapers/BC-07/

http://apotential.wordpress.com/2012/07/11/the-neurologist-explains-eegs-to-me/

Synaptic currents create a small electrical field along a neuron

If neurons are lined up, the electric fields add together.

x

Using electrodes placed on the scalp and sensitive amplifiers…

…one can record “brain waves”!

Glial Cells

There are several different typesOligodendrocytes – make myelin for axonsAstrocytes – help to provide food and “clean up” Microglia – Undertakers and “Homeland Security”:

detect and repel invaders and get rid of the deadEpendymal cells – BBBarrier & cerebrospinal fluidRadial glia – play a big role in development

(scaffolding and producing neurons)

Peripheral vs. Central Nervous System Myelin

~120g, 8 Billion Cells~1 Billion neurons(~11:1 glia:neurons)

~150g, 85 Billion Cells~70 Billion neurons(~1:4 glia:neurons)

~1250g, 75 Billion Cells~16 Billion neurons(~4:1 glia:neurons)

~1500 g, 170 Billion Cells~86 Billion neurons(~1:1 glia:neurons)

Getting a feel for the computing power of the brain

40 Million cellsThousands of connections each

Important properties of neurons Neurons have a negative “membrane potential” (i.e., inside has negative charge

compared to outside/CSF)

Neurons receive many signals that constantly change this “membrane potential”

Neurons will send a signal of their own if they become sufficiently “depolarized”

This signal, the Action Potential is a wave of “positivity” that propagates down the axon

Neurons can send signals quickly (~100 m/sec) to other neurons, muscles, glands etc.

Neurons have high energy demands, and low energy reserves.

Neurons do not divide and replace themselves – if damaged enough to die, they are not replaced (with few exceptions).