Final answer:
The parasympathetic ANS increases urinary output by triggering a spinal reflex that causes the contraction of the detrusor muscle and relaxation of the urethral sphincters. Additionally, inhibition of ADH release can contribute to increased urine production.
Step-by-step explanation:
The mechanisms that the parasympathetic autonomic nervous system (ANS) uses to increase urinary output can be explained through the actions of specific muscles and by considering hormonal responses. When the bladder becomes distended with urine, stretch receptors in the bladder wall trigger nerve impulses that travel to the sacral region of the spinal cord, setting off a spinal reflex. This reflex action results in the parasympathetic neural outflow that causes the contraction of the detrusor muscle in the bladder wall and relaxation of the internal urethral sphincter. Concurrently, there is inhibition of the somatic motor neurons which allows for the relaxation of the skeletal muscle of the external urethral sphincter, facilitating the expulsion of urine during micturition. Meanwhile, certain substances such as alcohol inhibit the release of antidiuretic hormone (ADH), which normally promotes water reabsorption in the kidneys, thus leading to increased urine production.