Problem: I also like that you explained the different roles of the internal and external urethral sphincters. One additional point is that the ureters don't rely on gravity to move urine-they use rhythmic peristaltic contractions, so urine can still travel from the kidneys to the bladder even when a person is lying down or upside down. Another interesting fact is that as the bladder fills, stretch receptors send signals to the spinal cord and brain, creating the urge to urinate. In healthy adults, the brain can temporarily delay urination by keeping the external urethral sphincter contracted until it's an appropriate time. How do you think damage to the spinal cord would affect a person's ability to control urination? Need Assignment Help?