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Published byAlexia King Modified over 9 years ago
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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”!
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Glial Cells There are several different types Oligodendrocytes – make myelin for axons Astrocytes – help to provide food and “clean up” Microglia – Undertakers and “Homeland Security”: detect and repel invaders and get rid of the dead Ependymal cells – BBBarrier & cerebrospinal fluid Radial glia – play a big role in development (scaffolding and producing neurons)
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Peripheral vs. Central Nervous System Myelin
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~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)
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Getting a feel for the computing power of the brain 40 Million cells Thousands of connections each
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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).
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