Puberty refers to the various changes that transform a child’s body into an adult one. Even before the teenage years, biochemical signals from the hypothalamus to the pituitary gland to the adrenal glands (the HPA axis) increase production of testosterone, estrogen, and various other hormones, which causes the body to grow rapidly and become capable of reproduction.
Some emotional reactions, such as quick mood shifts, are directly caused by hormones, as are thoughts about sex. The reactions of others to adolescents and their own reactions to the physical changes they are undergoing also trigger emotional responses, which, in turn, affect hormones.
Hormones regulate all the body rhythms of life, by day, by season, and by year. Changes in these rhythms in adolescence often result in sleep deprivation, partly because the natural circadian rhythm makes teenagers wide awake at night. Sleep deprivation causes numerous health and learning problems.
Puberty normally begins anytime from about age 8 to about age 14—
Girls generally begin and end puberty before boys do, although the time gap in sexual maturity is much shorter than the two-
Adolescents who reach puberty earlier or later than their friends experience additional stresses. Generally (depending on culture, community, and cohort), early-
The growth spurt is an acceleration of growth in every part of the body. Peak weight usually precedes peak height, which is then followed by peak muscle growth. This sequence makes adolescents particularly vulnerable to sports injuries. The lungs and the heart also increase in size and capacity.
All the changes of puberty depend on adequate nourishment, yet adolescents do not always make healthy food choices. One reason for poor nutrition is the desire to lose (or, less often, gain) weight because of anxiety about body image. This is a worldwide problem, involving cultural as well as biological factors.
Although serious eating disorders such as anorexia and bulimia are not usually diagnosed until emerging adulthood, their precursors are evident during puberty. Many adolescents eat too much of the wrong foods or too little food overall, with bingeing and obesity common.
Because of the sequence of brain development, many adolescents seek intense emotional experiences, unchecked by rational thought. For the same reason, adolescents are quick to react, explore, and learn. As a result, adolescents take risks, bravely or foolishly, with potential for harm as well as for good.
Various parts of the brain mature during puberty and in the following decade. The regions dedicated to emotional arousal (including the amygdala) mature before those that regulate and rationalize emotional expression (the prefrontal cortex).
Male–
Secondary sex characteristics are not directly involved in reproduction but signify that the child is becoming a man or a woman. Body shape, breasts, voice, body hair, and numerous other features differentiate males from females. Sexual activity is influenced more by culture than by physiology.
Among the problems that adolescents face is the tendency to become sexually active before their bodies and minds are ready. Pregnancy before age 16 takes a physical toll on a growing girl; it also puts her baby at risk of physical and psychological problems. Teen births are much less common today than earlier.
Sexual abuse, which includes any sexually provocative activity that involves a juvenile and an adult, is more likely to occur in early adolescence than at other ages. Girls are more often victims than boys are; perpetrators are often family members or close family friends. Rates are declining in the United States, but international sex trafficking is a global problem.
Untreated STIs at any age can lead to infertility and even death. Rates among sexually active teenagers are rising for many reasons.
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