During normal voiding the bladder and sphincters function in a co-ordinated manner. Urine is stored at low pressures till optimum capacity is reached. Once voiding is socially appropriate, the detrusor contracts, internal and external sphincters relax and voiding commences. If this orderly and complex sequence of events is disturbed neurogenic bladder disease happens with disastrous effects on the kidney. When the bladder is full, afferent impulses from bladder stretch receptors signal the sacral micturition centre causing detrusor contraction through the parasympathetic outflow and external sphincter relaxation through the pudendal nerve. The pontine micturition center in turn sends inhibitory impulses which relax the smooth muscle at the bladder neck thus initiating voiding.