Selling a house with a mortgage?

For arguments sake.If i was to buy a house for say �50,000 with a �45,000 mortgage putting down a �5000 deposit. Then a year later I was to sell that house for �60,000 and downsize to another house worth �50,000. What would happen to the �10,000 left over from the sale of the house? Would the bank take this to pay towards the mortgage or would it be paid to myself.