Our sexual response progresses through four stages:
Initial Excitement Genital areas become engorged with blood, penis becomes erect, clitoris swells, respiration and heart rate increase.
Plateau Phase Respiration and heart rate continue at an elevated level, genitals secrete fluids in preparation for coitus.
Orgasm Rhythmic genital contractions that may help conception, respiration, and heart rate increase further, males ejaculate, often accompanied by a pleasurable euphoria.
Resolution phase Respiration and heart rate return to normal resting states, men experience a refractory period-a time period that must elapse before another orgasm, women do not have a similar refractory period and can repeat the cycle immediately.
Psychological Factors in Sexual Motivation
Unlike many animals, our sexual desire is not motivated strictly by hormones. Many studies demonstrate that sexual motivation is controlled to a great extent by psychological rather than biological sources. Sexual desire can be present even when the capability to have sex is lost.
Studies show that homosexuality is not related to traumatic childhood experiences, parenting styles, the quality of relationships with parents, masculinity or femininity, or whether we are raised by heterosexual or homosexual parents. Although some researchers believe environmental influences probably affect sexual orientation, these factors have not yet been identified. Researchers have identified possible biological influences, however. Some studies indicate that specific brain structures might differ in size in brains of homosexuals when compared with the same structures in heterosexuals.