Question

why dont we fall from bed when we are asleep..?

Answer 1

When we sleep, a lot goes on in our bodies. We continue to breathe and growth hormone is released – we do not need to be awake for these things to happen. Similarly, we have some awareness of our body position and movements, and some people even manage to sit up or walk during their sleep! Most of us have enough awareness to ensure that we do not fall out of bed, but this ability develops over time. Young children are still growing and understanding how their bodies fit into the world around them, which is why they might benefit from a bedrail. 

Answer 2

because the gravity attract us