Are there sounds around us that we can't hear?

What's the impact of sodium on our heart health? Are there sounds around us that we can't hear? Why do teeth have nerves and a blood supply? What controls our emotions? Can other primates and mammals have colourblindness? Why can't certain organs regenerate themselves, whilst others can? Dr Chris Smith and Saskia Falken have the answers... Like this podcast? Please help us by supporting the Naked Scientists