When the urine volume in the bladder reaches 100-150 ml, it will cause bladder filling feeling. When the urine volume reaches 150-250 ml, there will be urine. When the urine volume reaches 250-450 ml, the bladder detrusor contraction due to nerve action, urine Can be excreted. Newborns can not control urination because the cerebral cortex is not yet fully developed. It is impossible to drain all the urine at once, because urine is formed all the time.