Biological Transitions
Learning Objectives
1. Understand the physical structures that are involved in biological
maturation during puberty.
2. Understand the processes through which the body changes during puberty.
3. Understand what occurs as females and males become sexually mature.
4. Understand the differences in when puberty occurs and how long it
takes to complete.
5. Understand how pubertal changes affect the individual and those
around him or her, especially in psychological ways.
6. Understand the connections between pubertal changes and eating disorders
such as anorexia nervosa and bulimia.
7. Understand physical health and health care during adolescence
Chapter Outline
I. Puberty: an overview.
· Puberty is primarily a stage of physical development, through
which an individual becomes capable of sexual reproduction
· There are five chief physical changes that take place during
puberty:
o Rapid acceleration in growth (height and weight)
o Development of primary sex characteristics (organs that allow reproduction)
o Development of secondary sex characteristics (external characteristics
that signal maturation)
o Changes in body composition (fat and muscle)
o Changes in circulatory and respiratory systems (strength and stamina)
A. The onset of puberty.
o The hormones that are central to puberty have been produced in smaller
quantities since before birth.
o Hormones serve two roles:
o Organizational: shape the brain and how it functions
§ Causes male and female brains to be different throughout life.
The structural difference leads to behavioral differences between males
and females. Higher levels of testosterone in males during prenatal development
may contribute to higher levels of aggression in males across the lifespan.
o Activational: certain hormonal changes occur during puberty that
activate physical changes; this activation causes the changes in primary
and secondary changes.
B. The endocrine system.
§ Endocrine glands produce and regulate levels of hormones in
the blood
§ Body tissues selectively “perceive” the instructions of hormones.
For example, adrenaline affects the heart in ways it does not affect other
tissue.
§ The brain, and specifically the hypothalamus, monitors the levels
of hormones in the blood, and maintains a set point or specific level of
hormones. The hypothalamus is the “thermostat” of the hormonal system.
§ The hypothalamus, pituitary gland, and the gonads (ovaries,
testicles) operate in a “feedback loop,” producing and maintaining the
levels of sex hormones (androgens and estrogens) that are mainly responsible
for the primary and secondary changes of puberty.
§ The hypothalamus “reads” the levels of hormones, instructs the
pituitary gland to release more or less hormones, which instructs the gonads
to produce more or less androgens or estrogens. When the hypothalamus perceives
there is a high enough level of sex hormones in the blood, it tells the
pituitary gland to stop increasing the levels of hormones.
§ The hypothalamus communicates with the pituitary gland by releasing
leutein hormone releasing factor and follicle-stimulating hormone releasing
factor
§ The pituitary gland communicates with the gonads by releasing
leutein hormone and follicle-stimulating hormone
C. Endocrine changes at puberty.
· For each individual, at the end of childhood, something causes
the hypothalamus to become less sensitive to the existing levels of sex
hormones in the blood. Therefore, the hypothalamus instructs the pituitary
gland to produce more hormones that activate the gonads to produce higher
levels of androgens and estrogens.
· The onset of puberty seems to be affected by the individual’s
psychological and physical health
· Besides releasing hormones that stimulate the gonads, the
pituitary gland releases hormones that stimulate the thyroid and the adrenal
cortex to produce hormones that stimulate physical growth.
II. Somatic Development
· The average teen grows 12 inches taller during puberty.
A. Changes in stature and the dimensions of the body
o Adolescent growth spurt – increase in height and weight
o The speed of the spurt is dramatic
o Peak height velocity for males is approximately 4.1 inches per year;
for females it is approximately 3.5 inches per year
o Growth spurt occurs, on average, two years earlier in females than
males
o Bones become much harder after the growth spurt. Those of African-Americans
are harder than those of Caucasians, contributing to the fact that Caucasians
are more likely to experience osteoporosis and bone fractures later in
life.
o Much of the height gain comes from increase in torso length
o The sequence of growth begins in the extremities (hands, feet) and
moves inward, with the torso growing in size last
o The different timing in the growth of body parts is referred to as
asynchronicity in growth
o Proportionately, males tend to gain more muscle weight, and females
more body fat, over the course of puberty
o The difference in muscle-to-body weight proportions tends to allow
males to outperform females in athletic events
o The difference in fat-to-body weight proportions tends to contribute
to females’ feelings of being overweight
o Females who mature early, begin dating early, and come from comparatively
affluent families tend to experience less satisfaction with their body
image
o Increases also occur in the size and capacity of the heart and lungs,
facilitating better athletic performance
B. Sexual maturation
o Secondary sexual characteristics, which are described by specific elements in the Tanner stages, occur as teens develop the external appearances of a man or a woman
1. Sexual maturation in boys
o The sequence of physical changes for males typically begins with changes
in the scrotum, testicles, and pubic hair, followed by the growth spurt
in height and growth of the penis, followed by growth of facial hair, followed
by changes in the vocal chords
o Changes in the skin and production of sweat and oils produces the
acne experienced by many adolescents
o Changes in the primary sexual characteristics (changes to the internal
organs and processes necessary for reproduction), influence the tendency
for the first ejaculation of seminal fluid, which tends to occur about
one year after the acceleration of penis growth
2. Sexual maturation in girls
o The sequence of physical changes for females typically begins with changes in the breasts and pubic hair, but is accompanied by the growth spurt in height. Menarche (the first menstrual cycle) is typically an event that occurs toward the end of pubertal changes. Regular ovulation tends to follow menarche by approximately two years.
III. The Timing and Tempo of Puberty
A. Variations in the timing and tempo of puberty
o Females tend to start puberty between ages 7 and 13
o Males tend to start puberty between ages 9.5 to 13.5
o There is no set time period for the length of puberty
o African-American females mature earlier than Caucasian females
B. Genetic and environmental influences
1. Individual differences in pubertal maturation
o The timing and tempo of pubertal maturation are primarily influenced
by one’s genes
o Everyone inherits a tendency for change that is written in his or
her genes, but the actual timing of pubertal changes can be influenced
by factors other than genes
o The two most important external factors are nutrition and health
o Puberty occurs earlier for individuals who have been extremely well
nourished throughout childhood, and for those who have not experienced
significant illnesses
o Excessive exercise is also associated with delayed pubertal changes
o Puberty tends to occur earlier for teens that grow up in conflict-ridden
families, and for females, in father-absent homes.
o Living in close proximity to one’s biological relatives appears to
slow the process of pubertal maturation.
o It may be that low stress in the family may speed maturation, while
high stress may impede maturation
2. Group differences in pubertal maturation
§ Average age of menarche is earlier in countries with better nutrition
§ Females in affluent homes tend to reach menarche earlier than
girls from poor homes
§ The secular trend: in industrialized countries over the last
150 years, females have reached menarche at earlier ages
§ While the secular trend has leveled off, it is likely that some
females will experience puberty at very young ages (e.g., ages 6 or 7)
IV. The Psychological and Social Impact of Puberty
· Hormones can directly affect behavior (e.g., sex drive)
· Physical changes cause changes in self-image, which affect
behavior
· Physical changes cause changes in how others treat the adolescent,
which affects how the adolescent behaves
· Cross-sectional research allows scientists to examine different
age groups at the same time, helping us understand age differences
· Longitudinal research allows scientists to examine the same
group over time (as the subjects get older), helping us understand changes
that occur as adolescents develop
A. The immediate impact of puberty
1. Puberty and self-esteem
· Going through puberty may lead to modest declines in self-esteem in girls, but only when accompanied by other life stressors (e.g., onset of dating, menarche, and changing schools in the same year)
2. Adolescent moodiness
· Adolescents are stereotypically thought to be moodier than
children or adults
· The “beeper study” determined that teens’ moods do fluctuate
more than adults’
· However, the direct connection between hormones and moods
is not very strong
· It may be the fluctuation rather than the dramatic increase
in hormones that influences moodiness
· While the moods of girls are related to levels of hormones,
life stressors seem to be more important predictors of mood
· Adolescent mood swings seem to parallel changes in activities
· Hormones may also affect the sleep needs of adolescents. There
may be a delayed phase preference for teens to stay up later and wake up
later than either children or adults
3. Puberty and family relations
· Puberty appears to increase the distance between parents and
children
· Minor conflicts increase, and positive exchanges decrease,
at least while the adolescent is going through puberty
· This change is not affected by the timing of puberty
· As they mature, adolescents tend to name peers rather than
adults (and parents) as the individuals who are most important to them
B. The impact of specific pubertal events
· Most teens interpret events such as menarche and first ejaculation
as positive events
· More “feedback” is provided to girls, however, regarding the
“seminal” event of puberty (menarche). Male development is not as “defined”
by one event (e.g., first ejaculation) nearly as strongly as is female
development
· The attitudes of girls toward menarche has become more positive
in recent years. The discussion of menstruation is more open than it has
been in the past.
· A female’s attitudes toward menarche influence her experience
of the event. Attitudes are also influenced by the discussions she has
had with her mother and her peers, as well as what she learns from the
media.
· A female’s attitude toward menarche is also influenced by
whether or not she is “on-time” versus early or late in relation to her
peers. Early or late maturers tend to have more negative attitudes toward
the event.
· Less research has been conducted regarding the impact of first
ejaculation on males, although existing research indicates it does not
carry nearly as much importance for males as menarche does for females
C. The impact of early or late maturation
1. Early versus late maturation among boys
· Early maturing boys tend to experience the changes in positive
ways
· However, there are also advantages for late-maturing boys.
They tend to have higher levels of intellectual curiosity, exploratory
behavior, and social initiative when compared to early maturers after all
individuals have completed puberty.
· It may be that late maturers have had a longer period of time
to “prepare” themselves for the changes of puberty.
· Early maturers tend to be more likely to get involved with
antisocial activities, including drug and alcohol abuse.
· Longitudinal research shows that, in early middle age, late
maturers tend to be more responsible, cooperative, self-controlled, and
more sociable, but are also more conforming, conventional, and humorless
than late maturers.
2. Early versus late maturation in girls
· Early studies found that early maturing girls were less popular,
less poised, less expressive, and more submissive and withdrawn than other
girls
· More recent research shows that early maturing girls have
more emotional problems, including problems with self-image, depression,
anxiety, eating disorders, and panic attacks.
· These findings tend not to apply to females in cultures such
as Germany, where attitudes toward sexuality and appearance are not as
important as they are in the U.S.
· Early maturing girls may experience more difficulties because
of the pressure they feel in relation to males, especially given the fact
that early maturing girls are more likely to associate with males who are
older than the females
· Early maturing girls are also more likely to become involved
in deviant activities such as drug and alcohol abuse
· However, early maturing females who attend all-girl schools
do not seem to experience the same difficulties
· Once they reach adulthood, like their male counterparts, early
maturing females tend to be more psychologically advanced than other females
· However, they tend to have lower educational aspirations
V. Pubertal Changes and Eating Disorders
· Basal metabolic rate decreases about 15 percent during puberty
· Approximately 20% of current females are overweight, and 5%
are obese
· Obese adolescents will likely (80%) continue to be obese as
adults, and this is accompanied by a variety of health risks (e.g., hypertension,
high cholesterol, and diabetes)
· Disordered eating patterns are common among adolescents
A. Anorexia nervosa and bulimia
· Bulimia is a disorder characterized by overeating followed
by self-induced vomiting (or the use of laxatives or excessive exercise)
in order to avoid weight gain
· Anorexia nervosa is a disorder characterized by continued
self-induced food deprivation
· Adolescents with either eating disorder have a disturbed body
image
· Perhaps as many as 20% of anorexic adolescents starve themselves
to death
· Approximately 0.5% of teens are anorexic, and 3% are bulimic
· Dissatisfaction with body image is pervasive among teenage
girls, however
· Recent research shows that this problem is pervasive among
females from a variety of ethnic and socioeconomic backgrounds
· Some theories of eating disorders point to genetic or hormonal
differences, while other point to dysfunctional family dynamics (e.g.,
overcontrolling parents)
· A third possible explanation is that eating disorders is but
one aspect of a generalized psychological difficulty called internalized
distress
· Finally, some scientists point to the socio-cultural pressure
that is placed on females to be thin, a stressor that males do not experience
as harshly
VI. Physical Health and Health Care in Adolescence
· Adolescence, in general, is a very healthy time of life
· However, it is also a time of great risk, because adolescents
engage in behaviors that can result in health problems (drug use, aggression,
unprotected sex, drunk driving)
· The death rate from violence and injury increased between
1950 and 1985
· Approximately 40% of teen deaths result from car accidents,
and another 35% are a result of homicide or suicide
· Many minority youth are at greater risk than Caucasians for
health problems or death, and have less access to sources of medical care
· Health promotion among adolescents has addressed the fact
that most of the health and morbidity problems result from choices teens
make regarding their own behavior (e.g., smoking, driving drunk)
· Practitioners focus now on promoting health-enhancing behaviors
and steering teens away from health-compromising behaviors
· Successful health promotion includes:
o Establishing a trusting relationship with a teen prior to adolescence
o Talking to teens about healthy and non-healthy behaviors
o Offering sound advice about healthy behaviors
o Encouraging teens to participate in health-promoting programs
o Following up with teens after participation
· School-based health centers now offer teens health services
· Studies show that teens attitudes (at least) are often changed
after the use of these health centers
Study Questions
1. What is puberty?
2. What are the five chief physical developments of puberty?
3. What are the organizational and activational role of hormones during puberty? Briefly explain.
4. How does the feedback associated with the onset of puberty operate?
5. What happens to the feedback loop that allows for the onset of puberty?
6. What is the adolescent growth spurt?
7. Are there gender differences in the growth spurt? Explain.
8. What is asynchronicity in growth?
9. How does the muscle-to-fat ratio change in males and females?
10. What are the biological and environmental influences that underly the gender differences in circulatory and respiratory capacity that are evident following puberty?
11. What is the general sequence of sexual maturation (Tanner stages) in boys?
12. What is the general sequence of sexual maturation (Tanner stages) in girls?
13. What are two environmental influences on pubertal timing and tempo?
14. How do environmental influences affect pubertal timing & tempo in individuals of:
other countries?
different socio-economic groups?
different historical eras?
15. What is the secular trend?
16. What is the immediate impact of puberty on:
self-esteem?
moodiness?
family relations?
17. How do early adolescent females respond to menarche?
18. How do early adolescent males respond to first ejaculation?
19. What are the immediate and long-term psychological and social consequences of early and late maturation in females?
20. What are the immediate and long-term psychological and social consequences of early and late maturation in males?
21. What are the social and psychological parallels between the early maturing female and the late maturing male?
22. What are the deviance hypothesis and the developmental readiness hypothesis when discussing the impact of early and late maturation?
23. How are the pubertal changes of early adolescence associated with the emergence of eating disordered behavior in young adolescent females?
24. What are three health-compromising behaviors?
25. What are three health-enhancing behaviors?
26. What are Irwin's five As of successful health promotion with adolescents? Describe.
27. What are the “old" and the "new" mortalities in adolescent health?
28. Are there racial and ethnic differences in these "old" and "new" mortalities? Explain.
Multiple Choice Questions - Please circle the correct answer.
1. The development of primary sex characteristics is evidenced by:
a. a rapid change in height and weight
b. growth and development of the breasts
c. growth and development of the ovaries
d. changes in the distribution of fat
2. The ___________ system is responsible for producing, regulating and
circulating levels of hormones in the body.
a. autonomic nervous
b. endocrine
c. central nervous
d. circulatory
3. The hypothalamus is part of which bodily system?
a. Autonomic nervous
b. Endocrine
c. Central nervous
d. Circulatory
4. The gland that controls hormone levels in the body is:
a. the pituitary gland
b. the adrenal gland
c. the thyroid gland
d. the ovarian gland
5. Lutenizing hormone-releasing factor and follicle-stimulating, hormone-releasing
factor is secreted by:
a. the pituitary gland
b. the adrenal gland
c. the hypothalamus
d. the ovaries
6. The adolescent growth spurt:
a. begins earlier in girls than in boys
b. begins earlier in boys than in girls
c. begins at about the same time in both genders
d. begins in both genders toward the end of puberty
7. Muscle growth during puberty occurs:
a. only in males
b. only in females
c. in both genders
d. very slowly in females
8. A very early development in the pubertal sequence of males is:
a. the emergence of facial hair
b. the voice change
c. penis growth
d. testes and scrotum growth
9. A late development in the pubertal sequence of females is:
a. breast development
b. growth of pubic hair
c. menarche
d. growth spurt
10. The average age of menarche in the United States and Western Europe
is ______ in comparison to the average age of menarche in Africa.
a. lower
b. higher
c. about the same
d. impossible to calculate
11. Researchers looking at the association between puberty and moodiness
in adolescence have concluded that the relationship is:
a. nonexistent
b. weak to moderate
c. strong
d. very strong
12. Csikszentmihalyi and Larson have found that adolescent mood swings
parallel:
a. their fights with their parents
b. their grades in school
c. their relationships with the opposite sex
d. their changes in activities
13. The analogous process in males to female menarche is:
a. penis growth
b. first ejaculation
c. development of the testes
d. the voice change
14. Brooks-Gunn and colleagues have found that female adolescents tend
to respond positively to:
a. breast development
b. the growth spurt
c. menarche
d. pubic hair growth
15. Late maturation in males has generally been found to be a _______
psychological and social experience.
a. positive
b. negative
c. neutral
d. unimportant
16. One of the long-term, socio-emotional issues associated with early
maturation in males is:
a. low self-esteem
b. irresponsibility
c. uncooperativeness
d. lack of inventiveness
17. One of the short-term, socio-emotional issues associated with early
maturation in females in the United States is:
a. low self-esteem
b. irresponsibility
c. uncooperativeness
d. lack of inventiveness
18. Approximately ____ percent of American adolescents are overweight.
a. less than 5
b. 10
c. 20
d. 33
19. Approximately___ percent of American adolescents suffer from anorexia
nervosa.
a. less than 5
b. 10
c. 20
d. 33
20. A contributor to the "new morbidity and mortality" in adolescence
is:
a. chronic illness
b. substance abuse
c. physical disabilities
d. dental difficulties
21. One of Irwin's five As of successful health promotion is:
a. anticipatory guidance
b. argument
c. AID's talk
d. availability
22. The term "peak height velocity" refers to:
a. when the adolescent reaches his or her adult height
b. when the adolescent feels his or her growth begin
c. when the adolescent is growing most rapidly
d. when the adolescent is gaining height and weight simultaneously
23. The sequence of sexual maturation for both male and female adolescents
are described in _______ stages.
a. Piagetian
b. Tanner
c. Masters and Johnson
d. Freudian
24. A cross-sectional study involves gathering information:
a. from groups of individuals of different ages
b. from groups of individuals over time
c. from groups of individuals from different regions of the country
d. from groups of individuals representing both genders
25. Which group of adolescents evidence the highest rates of drug and
alcohol use in early adolescence?
a. Late maturing males
b. Average maturing males
c. Early maturing males
d. None of the above
True/False Questions - Mark each statement either True (T) or False (F).
1. The pubertal process begins at about the same age in males and females.
2 In the feedback loop, associated with the onset of puberty, the pituitary gland releases androgen.
3. The hypothalamus is part of the endocrine system.
4. Adrenarche may be related to early feelings of sexual attraction.
5. During puberty, males are more concerned about their weight than females are.
6. On average, the growth spurt occurs earlier in males than females.
7. One of the earliest manifestations of the pubertal process in females is menarche.
8. There is no relationship between gender and self-esteem during early adolescence.
9. Researchers have found considerable evidence for the role of "raging" hormones in the moodiness of young adolescents.
10. Among males, early maturers report greater popularity and higher self-esteem.
11. Early maturing females appear to benefit from earlier maturation just like early maturing males.
12. Late maturing males evidence more deviant behavior (like drug and alcohol abuse) than early maturing males.
13. Early maturing females are more popular with the boys than late maturing females.
14. The developmental readiness states that young people who stand apart from their peers are likely to experience more psychological distress than adolescence who don't appear different.
15. Anorexia nervosa is more prevalent than obesity among young people.
16. Eating disorders are most prevalent among affluent, white females.
17. On average, adults are involved in more driving accidents than adolescents are.
18. Irwin believes that it's important not to be direct with adolescents about health- promoting behaviors because that will turn them off to more positive approaches.
19. Only males gain muscle during the pubertal process.
20. A good example of the activational role of hormones during the pubertal process is the way that hormones shape the brain prenatally.
21. The appropriate level of a hormone in the body is called the set point.
22. The average adolescent gains about six inches in height as a result of puberty.
23. The term "asynchronicity in growth" refers to the tendency for different youngsters to begin puberty at different times.
24. Gender differences in circulatory and respiratory capacity following puberty are largely due to gender differences in hormones.
25. The unfolding of the secondary sex characteristics in males is more orderly than the analogous process in females.
26. A very early sign of puberty in females is the breast bud.
27. Diet and medical care can influence the onset of the pubertal process.
28. The secular trend refers to the tendency for adolescents of different religious backgrounds to experience the onset of puberty at different ages.
29. Adolescents appear to have a biological preference to go to bed later and get up later than younger children.
30. Puberty is associated with increased distance between parents and children.
Matching Questions - Choose the term that most accurately fits the description.
___ 1. appropriate hormone level
a. puberty
___ 2. sex glands
b. seconary sex characteristics
___ 3. rapid change in height & weight
c. central nervous system
___ 4. sequence of sexual maturation
d. hormones
___ 5. regulates hormones
e. endocrine system
___ 6. set up like a thermostat
f. set point
___ 7. highly-specialized substances
g. feedback loop
___ 8. involves different groups of individuals
h. pituitary gland
i. hypothalamus
___ 9. involves starvation
j. gonads
___ 10. manifestation of breasts, pubic and facial hair
k. adrenarche
l. adolescent growth spurt
___ 11. gland that controls hormone levels
m. asynchronicity in growth
___ 12. follows the same individuals over a time period
n. Tanner stages
o. cross-sectional study
___ 13. creates gawkiness and awkwardness
p. longitudinal study
___ 14. controls the pituitary gland
q. delayed phase preference
___ 15. involves eating binges and vomiting
r. anorexia nervosa
___ 16. the process of becoming capable of reproduction
s. bulimia
t. health-enhancing behavior
___ 17. going to bed late and sleeping late
___ 18. maturation of the adrenal glands
___ 19. bodily system of which hypothalamus is a part
___ 20. activities like exercise and proper diet
Answer Key
Multiple Choice Questions
1. c 11. b 21. a
2. b 12. d 22. c
3. c 13. b 23. b
4. a 14. a 24. a
5. c 15. b 25. c
6. a 16. d
7. c 17. a
8. d 18. c
9. c 19. a
10. a 20. b
True/False Questions
1. F 11. F 21. T
2. F 12. F 22. F
3. F 13. T 23. F
4. T 14. T 24. F
5. F 15. F 25. T
6. F 16. F 26. T
7. F 17. F 27. T
8. F 18. F 28. F
9. F 19. F 29. T
10. T 20. F 30. T
Matching Questions
1. f 11. h
2. j 12. p
3. l 13. m
4. n 14. i
5. e 15. s
6. g 16. a
7. d 17. q
8. o 18. k
9. r 19. c
10. b 20. t