Sexual stimulation and friction provide the impulses that are delivered to the spinal cord and into the brain. Ejaculation is a reflex action controlled by the central nervous system<span>. It is triggered when the sexual act reaches a critical level of excitement. It has two phases.</span>
When you're aroused, tubes called the vas deferens squeeze sperm<span> from the testes toward the back of the urethra. The seminal vesicles also release fluid there.
