March 14, 2007

communication of neurons

Well, we're in the middle of spring break right now. I have been out of town for a couple of days, visiting some family and what not, so I haven't really had time to update my blog. But finally today I have some interesting stuff to write about and the free time to do it!

Today I'm going to describe a couple of press releases that I have been meaning to post about, which concern the neuron. Neurons are the cells that make up the nervous system (brain, spinal cord, peripheral nerves) and they process and transmit information throughout the body. At the moment, we are going to be concerned with how these neurons communicate.

The current accepted view of how neurons transmit information is by synaptic transmission through a electrochemical process. Here is my very brief and general description of such transmission: Basically, neurons receive chemical messages (neurotransmitters) from other neurons through receptors, which are located on their dendrites (tree branch looking extensions from cell body). Once dendrites receive the message, an electrical impulse is generated that travels down to the soma (cell body) and along the axon (another extension from the soma in opposite direction of the dendrites). At the end of the axon are terminals that contain vesicles that release a neurotransmitter to the next receiving neuron. The neurotransmitter is released into a synapse, which is a microspace between the terminals of the preceding neuron (presynaptic terminals) and dendrites of the following neuron (postsynaptic dendrites). So neuron communication in real basic terms: neighbor neuron releases chemical, chemical is received and causes electrical impulse in next neuron who then releases another chemical to it's next neighbor and so on. All chemical transmission is done through the synapse, hence the name "synaptic transmission." There, now that wasn't too bad I guess . . .

Well, a group of physicists from Copenhagen University are not really too satisfied with this explanation of nerve cell communication. Reasoning? Electrical impulses should produce heat, such heat has not been observed in the neuron, therefore electrical impulses are not generated along the axons. Instead, they propose that neurons transmit impulses of sound.

"Heimburg and Jackson theorize that sound propagation is a much more likely explanation. Although sound waves usually weaken as they spread out, a medium with the right physical properties could create a special kind of sound pulse or "soliton" that can propagate without spreading or losing strength. The physicists say because the nerve membrane is made of a material similar to olive oil that can change from liquid to solid through temperature variations, they can freeze and propagate the solitons."
This seems to be mostly theoretical work, the news article doesn't describe any of the research that the group has done on the topic. I'm not willing to buy into it, not at the moment anyways. They have a lot of work to do if they want to stand against the decades of research on the electrical activity of neurons. By the by, how in the world would we be able to measure the electrical activity in the brain through EEG if neurons did not generate electricity? Just not ready to give up the electro-chemical explanation I guess.

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