>>13895119You've got two urinary sphincters (valves) that both need to open to release urine. The outer sphincter is like the lungs: usually on autopilot but you can take direct control and force it to open and close. You don't have any direct control over the internal sphincter. It's controlled by a subconscious part of the brain and only opens when you feel it's safe to urinate.
In addition to the urinary sphincters you've got a muscle that squeezes urine out of the bladder (the detrusor). You don't control this muscle either. It activates automatically when the bladder is full and doesn't stop until it's empty. You can have half your body deciding it's time to piss and half your body deciding not to let you piss.
