An example would be a nocturnal emission, or wet dream. Nocturnal emissions are common in adolescence and in men who are not sexually active. They are the result of erotic stimuli in the absence of either masturbation or sexual intercourse. The second type is a combination of friction associated with input from the central nervous system. This is the typical ejaculation that men are most familiar with.
Ejaculation is divided into several events.
Sexual stimulation and friction provide the impulses that go into the spinal cord and into the brain. The autonomic nervous system will stimulate the sympathetic nerves to cause contraction of the male accessory sexual organs including the vas deferens, prostate, and seminal vesicles. This results in a seminal emission, which is composed of the sperm and the seminal fluid from both the prostrate and seminal vesicles. This emission is deposited in the posterior urethra. The ejaculation occurs when there is contraction of the bulbocavernosus muscle propelling the semen out of the penis.