Final answer:
The orgasm phase is the stage in the sexual response cycle which involves the discharge of neuromuscular tension built up earlier, characterized by rhythmic pelvic contractions and possible ejaculation.
Step-by-step explanation:
The discharge of the neuromuscular tension built up during the excitement and plateau phases is known as the orgasm phase of the sexual response cycle. In this phase, individuals experience rhythmic contractions of the pelvis accompanied, in females, by uterine contractions and, in males, by ejaculation. These contractions reflect the activity of motor neurons that stimulate the muscles to contract in a manner similar to muscle twitches and tetanus observed in muscle physiology. However, during an orgasm, these contractions are rhythmic and coordinated, leading to the peak feeling of release in the sexual response cycle as established by Masters and Johnson.