"To truly understand how these parts function during sexual intercourse, we need to consider a research-based paradigm developed by Masters and Johnson years ago which they called the sexual response cycle. The sexual response cycle is a model that explains how most people experience three phases when they engage in sexual intercourse: excitement, plateau, and then orgasm. Masters and Johnson are quick to point out that each individual has a unique and varied sexual response, so much so that no two sexual encounters would be expected to be perfectly identical between the same people. Nevertheless, these three phases are very common among most people. As sexual intercourse begins, both males and females pass through three phases. The excitement phase is when blood flows to the pelvis, bringing more lymphatic fluid and plasma to the region. Because of hormonal and psychological stimuli, there is generally swelling in the sexual parts. While this is happening, the plateau phase begins, which is when more hormones are released, moisture increases, heart rate increases, and intensity of sensory perception increases, including touch, smell, sight, hearing, and taste. In the orgasm phase, an electrical buildup of energy is released that is associated with a rhythmic contraction of the pelvic floor muscles, the urinary and anal sphincters, and various glands for males. This is called an orgasm. After the orgasm finishes, resolution eventually allows the sexual parts to return to pre-excitement conditions. These are almost identical in every way between males and females, except that there are differing sexual parts for each."