ABSTRACT
Normal male sexual function depends on the sexual response cycle, which consists of an anticipatory libidinous state (sexual motive or desire), effective vasocongestive arousal (erection), orgasm, and resolution (detumescence). Libido is defined as the biological need for sexual activity and frequently is expressed as sexseeking behavior. Its intensity is variable between individuals as well as within an individual over a given period of time. Little is known about the physiological basis of libido. Erection, however, is associated with significant psychological and physical changes. This is the ultimate response to multiple psychogenic and sensory stimuli from imaginative, visual, auditory, olfactory, gustatory, tactile, and genital reflexogenic sources, which trigger several neurological and vascular cascades that produce penile tumescence and rigidity sufficient for vaginal penetration. The sensation of orgasm is accompanied by two sequential functions: emission and ejaculation. Emission, mediated by contractions of the prostate, seminal vesicles, and urethra, produces a sensation of ejaculatory inevitability and deposition of semen in the posterior urethra. Generalized muscular tension, perineal contractions, and involuntary pelvic thrusting (every 0.8 seconds) usually follow and lead to the expulsion of semen from the urethral meatus. The resolution phase returns the penis to the flaccid state and provides a sense of general pleasure, well-being, and muscular relaxation. During this period, men are physiologically refractory to subsequent erection and orgasm for a variable amount of time. (For further information on normal male sex physiology, see Chapter 3.)
Disorders of the sexual response may involve one or more of the cycle’s phases; these may be generalized or limited to certain situations or partners or may be lifelong (i.e., there has been no evidence of any effective sexual performance, generally due to persistent intrapsychic conflicts) or acquired (dysfunction arises after a period of normal function). Although there are no universally acknowledged defining criteria, a period of persistence over three months has been suggested as a
reasonable guideline for clinical concern. Isolated dysfunction of the erectile mechanism is the most common problem, but generally, disturbances may occur in some or all of the subjective components of desire, arousal, and pleasure and the objective components of performance, vasocongestion, and orgasm, although any of these may be affected independently.
