Part of the show Cardiologist Peter Weissberg talks about heart disease
You must have noticed that when a smell comes your way, initially, you can smell it very strongly, but as time passes you notice it less and less, such as when you walk into someone else's house for instance, or into a restaurant. Scientists call this process 'adaptation', or odour desensitisation, and both animals and humans use it so that we can tell whether a scent it getting stronger or going away The nose is essentially a collection of nerve cells, some of which fire off signals to the brain when a certain smell is detected. When an odour is present, if you measure the electrical activity in these nerve cells, it slowly declines over time as you get used to the smell. But recently two teams of scientists in America have found that this process does not happen in mice that lack a gene that makes a protein called CNGA4. In these mice, when an odour is presented, the level of activity in the nerves in their noses remains high and they just keep on smelling it. Although the scientists haven't yet figured out exactly how CNGA4 works, they think that it probably helps to close off channels that kick start the cell into sending messages, called action potentials, to the brain. This means that the mice without CNGA4 cannot switch off their smell-sensitive nerve cells and so they keep on smelling the odour !