Answer:
When the internal urethral sphincter relaxes, feedback through the autonomous nervous system relaxes the other urethral sphincter.
Explanation:
The urine is passed down through the urethra, in order for its extraction of the waste products from the human body. As the smooth muscles are present in the urinary system which dilates and contracts accordingly with the regulation mechanism implemented by the hypothalamus(part of a brain). And the process is initiated and then terminated by the autonomous nervous system, which controls the smooth muscle contraction and relaxation for giving the pathway for the urine removal from the human body.
