Final answer:
The pelvic splanchnic nerves provide parasympathetic innervation to the bladder, promoting urination by contracting the detrusor muscle when necessary.
Step-by-step explanation:
The nerves that bring parasympathetic innervation to the bladder are the pelvic splanchnic nerves. These nerves control the parasympathetic aspects of bladder function, such as stimulating the detrusor muscle to contract and allow for urination. While the hypogastric nerves are responsible for the sympathetic actions, which suppress detrusor muscle contractions, the pelvic splanchnic nerves carry out the opposite function. Additionally, somatic nerves, especially the pudendal nerve, play a role in the voluntary control of the external urethral sphincter.
Normal micturition is facilitated by a reflex arc in which stretch receptors in the bladder wall send impulses through the sacral spinal cord region, leading to parasympathetic outflow that causes contraction of the detrusor muscle. To allow effective urination, somatic motor neurons are inhibited, which relaxes the external urethral sphincter.