Orgasm
The penis usually becomes erect (hard) before an orgasm, and flaccid (soft) again after. When a man has an orgasm, his penis spasms and undergoes a series of rhythmic contractions, during which he feels a very strong and enjoyable feeling in his penis and groin, and sometimes in all of his body. In a man, an orgasm usually happens at the same time as an ejaculation, which is a release of semen through the penis that can't be stopped. Young boys can orgasm, but there may be no semen because semen release usually occurs (happens) only after puberty has started. After an orgasm, men usually have a deep sense of relaxation, usually felt in the groin and the thighs. Usually the stronger the orgasm is, the deeper the relaxation and the longer the relaxation will last. This is due to the dopamine surge in the brain.