Taste and Smell

The actual tastebuds in the tongue can distinguish only four different tastes. We can distinguish literally thousands of different smells, using nerve cells in the back of the nose that can detect just a few molecules of an odor. These receptors are renewed at least one a month, the only nerve cells to be replaced. They are wired directly into the lowest levels of the brain, without passing through the parts of the brain involved in thought. That's why smell arouses emotions instantly, and revives memories we may have long forgotten.