From neurons to brains (Introduction)

by David Turell , Tuesday, February 17, 2015, 00:30 (3362 days ago) @ David Turell

Early neurons are not as complex as the current ones in the brain. Neurons may date back 600 million years.-"Our research group has been discovering evidence for a long time that most major signaling systems in our neurons are ancient, but we never really knew when they first appeared," Jegla said. "We had always assumed that we would be able to trace most of these signaling systems to the earliest nervous systems, but in this paper we show that this is not the case. It looks like the majority of these signaling systems first appear in the common ancestor that humans share with jellyfish and sea anemones."-Electrical impulses in nerve cells are generated by charged molecules known as ions moving into and out of the cell through highly specialized ion-channel proteins that form openings in the cell membrane. The new research focuses on the functional evolution of the genes that encode the proteins for potassium channels—ion channels that allow potassium to flow out of nerve cells, stopping the cell's electrical impulses. "The channels are critical for determining how a nerve cell fires electrical signals," said Jegla. "It appears that animals such as sea anemones and jellyfish are using the same channels that shape electrical signals in our brains in essentially the same way."-"We don't yet understand why our ion channels evolved at that time, but the changes in the ability of nerve cells to generate electrical signals must have been revolutionary," said Jegla. "Our current favorite hypothesis is that neurons capable of directional signaling might have evolved at this time." In human nervous systems, most nerve cells have a polar structure with separate regions for inputs and outputs. This allows for directional information flow and highly complex circuits of nerve cells, but it requires a huge diversity of ion channels to shape the electrical signals as they pass through the polar nerve cells. "If our hypothesis turns out to be correct, we may be able to gain some important insights into how nerve cells and circuits evolved by studying sea anemones," said Jegla. "There is a lot that remains to be discovered about how we build polar neurons, and we can use evolution to point out the really important mechanisms that have been conserved through animal history."- Read more at: http://phys.org/news/2015-02-complex-nerve-cell-common-ancestor-humans.html#jCp