In a traditional sense, your mum is right. The five senses first codified by Aristotle are: sight, hearing, touch, smell and taste. But modern science recognizes at least six other senses including: pain, balance, joint motion, time, temperature, and in some people a sense of direction. Wikipedia has a good article about the senses. There are a few more internal senses that detect the stretching of organs such as the bladder and lungs.