Understanding Psychology (10th Ed)

erogenous zones
Areas of the body 
that are particularly sensitive because 
of the presence of an unusually rich 
array of nerve receptors.
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 Module 
33 
Understanding Human Sexual Response: The Facts of Life 
359
In the
 excitement phase , 
which can last from just a few minutes to more than 
an hour, an arousing stimulus begins a sequence that prepares the genitals for sexual 
intercourse. In the male, the penis becomes erect when blood fl ows into it. In the 
female, the clitoris swells because of an increase in the blood supply to that area, and 
the vagina becomes lubricated. Women may also experience a “sex fl ush,” a red rash 
that typically spreads over the chest and throat.
Next comes the
 plateau phase, 
the body’s preparation for orgasm. During this 
stage, the maximum level of sexual arousal is attained as the penis and clitoris swell 
with blood. Women’s breasts and vaginas expand, heartbeat and blood pressure rise, 
and breathing rate increases. Muscle tension becomes greater as the body prepares 
itself for the next stage, orgasm. Although it is diffi cult to explain the sensation of 
 orgasm 
beyond saying that it is an intense, highly pleasurable experience, the bio-
logical events that accompany the feeling are fairly straightforward. When the orgasm 
stage is reached, rhythmic muscular contractions occur in the genitals every eight-
tenths of a second. In the male, the contractions expel semen, a fl uid containing 
sperm, from the penis—a process known as ejaculation . For women and men, breath-
ing and heart rates reach their maximum.
After orgasm, people move into the last stage of sexual arousal, the