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Showing posts from July, 2007

The sea inside your skull - ion homeostasis

Previous posts have covered a number of the low-level building blocks that are used by cells in the brain - things like ion channels, neurotransmitters, receptors, clathrin, vesicles, etc. This post focuses on some important pieces of infrastructure that are needed to enable the brain to do its thing. 

Neurons operate in an aqueous medium - a kind of salt water bath, water that is full of postively charged ions (cations like sodium, potassium and calcium) and negatively charged ions (anions like chlorine).   Water molecules are V shaped and have a non-uniform distribution of charge - i.e. one end of the water molecule is more positively charged than the other end.  Like charges repel and unlike charges attract.  As a result, a sphere of these 'polar' water molecules tends to surround the ions (a 'sphere of hydration').   Complicating the picture further is the fact that charged particles like ions are influenced by both concentration gradients (ions flow to the region …