Why do I wake if I hear a noise?

Why do I wake if I hear a noise?

Chris Idzikowski (Director of the Edinburgh Sleep Centre) gives expert video advice on: What happens to my brain when I sleep?; What happens to my muscles when i sleep?; What happens to my breathing when I sleep? and more...

We don't necessarily awaken when we hear a noise. The lower level senses will work out whether there is a need to awaken. So if it's an alarm or a really odd sound then the brain will start to wake itself up. Not so true in deep sleep, it's much harder to arouse the brain at that point. It's also quite difficult in dreaming sleep, because the sound can get incorporated into the dream as well. But it's a low level sort of response to, well, what's this about? And if it's a question that can't be answered then the rest of the brain is brought in to work it out.