How does the bladder hold back the urine?

Answer:
With the sphincter muscle, found at the junction of the bladder and the urethra.

Involuntary muscles. There is a whole part of the brain that controls involuntary responses and functions. Example:breathing, heart pumping blood.
First answer by LeftCoastMom. Last edit by Rumba. Contributor trust: 229 [recommend contributor recommended]. Question popularity: 1 [recommend question].