Fish have all sorts of senses that they use at different stages in their lives to know where they are; they can smell, they can hear, they may have the ability to sense magnetic fields.  Because Fish eggs float around coral reefs, you would expect to get a mix of genetically different fish on different reefs, but research shows that there are clusters of fish that stick to the same reefs.

Reefs are actually very noisy - you can hear fish nibbling at coral, and things like snapping shrimps adding to the noise.  By making artificial reefs and playing this noise in some, but not in others, researchers saw that fish would stay around the noisy reefs - proving that the fish could hear the reef.  There is also evidence that fish can smell similar fish - which could be how salmon know which river to return to.

This is a result of an emotional response to the music.  Goosebumps form at the base of a hair, where the hair sticks out from the skin.  When hairy animals are scared they look bigger, and this would have applied to us when we were much hairier animals.  This is because all the hairs stand on end - they are lifted by muscles called erector muscles - piloerection is the term for hair standing on end.  When you're scared, or have an emotional response to something, these muscles make your hair stand on end – making you look bigger and reducing heat loss by trapping more air.  This is controlled by a region of the brain called the hypothalamus, which controls the sympathetic nervous system – the part involved in the ‘fight or flight’ response.  If you are threatened, you need to look bigger to scare off an opponent, and also look redder, as this suggests more testosterone and more anger.

So when a piece of music excites you, your hypothalamus can respond by exercising the fight or flight response, and so you get goose bumps!

A toothache is when you have irritation to the nerve supply to a tooth.  The most common reason for this is sensitivity to cold, when you have sensitive teeth, but usually it’s because you have a hole in your tooth – a carie.  Holes in teeth are caused by bacteria, usually streptococcal bacteria, metabolising sugars in your diet into acids, which then drill holes in teeth.  Teeth are made of calcium phosphate, and so can be dissolved by acid.

When the hole becomes big enough, the bacteria can start to change the chemical environment inside the tooth, and you can get abscesses. These are painful because they cause inflammation and swelling, or just because of the change in chemistry.

Another less common, but very serious cause of toothache can be an infection in a sinus.  The nerves that supply your teeth run through, for example, the floor of the maxillary air sinus, the sinus behind your cheek.  An infected sinus could make you feel that you have a toothache, when there’s nothing wrong with your teeth.

We put this question to Roger Pedersen, from the University of Cambridge.

That’s a very good question.  If we can culture embryonic stem cells in the Petri dish it looks like if we keep them happy, and give them what they want to be healthy, the answer is yes.  They seem to do very well genetically for a long period of time.  The thing that makes it intriguing is that possibly our bodies have the same kind of molecular insulation and possibly other tools to make stem cells last longer in a stable and completely normal state.

I do because we know about a stem cell, which is called the O2A cell which is a stem cell which we think is in the brain already and whenever anyone has a flare up of MS and the nervous system gets attacked by the immune system which destroys the myelin, that surround nerve cells, we think the reason they get better afterwards, at least for a time, is because these stem cells reawaken and produce new myelin-producing cells. Do you think that’s reasonable Roger?

In fact, there's a team of scientists at Cambridge University working on that very problem!