Chapter One: Fundamental Changes of Adolescence: Biological Transitions Flashcards
What is Puberty
It is the period during which an individual becomes capable of sexual reproduction. Hormones regulated by the endocrine system lead to physical
changes. No new hormones are produced and no new bodily systems develop
at puberty.
What does the endocrine system do?
Produces, circulates and regulates hormone levels in the body.
Hormones
Specialized substances secreted by endocrine glands.
Glands
Organs that stimulate particular parts of the body to respond in specific ways.
Gonadotropin-releasing hormone neurons (GnRH)
Neurons in the brain that play important roles in puberty.
What does the feedback loop do?
Levels of sex hormones are regulates (to a set point) by the hormonal feedback system composed of the hypothalamus, pituitary gland, and gonads.
Process of the hormonal feedback loop
The hypothalamus monitors sex hormones and then controls the pituitary gland, which signals the gonads, which release sex hormones.
Adrenarche
Maturation of the adrenal gland that takes place during adolescence. Changes in the brain system regulates the Arenal gland, which is also the system that controls how we respond to stress.
Cortisol
A hormone that is produced when a person is exposed to stress.
What triggers puberty?
Something in middle childhood reawakens the HPG axis and signals that the body is ready for puberty:
• Presence of mature sexual partners
• Sufficient nutritional resources
• Physically healthy enough to begin reproducing
Other factors:
- genes predispose onset at a certain age
- more fat cells, more exposure to light, triggers puberty earlier
What are the brain chemicals that stimulate the onset of puberty?
Kisspeptin : A brain chemical believed to trigger the onset of
Leptin : A brain chemical produced by the fat cells that may play a role
in the onset of puberty through stimulating kisspeptin.
Melatonin : A hormone secreted by the brain that contributes to
sleepiness and that triggers the onset of puberty through its impact on
kisspeptin.
How do hormones influence adolescent development?
Organizing Role:
•Prenatal hormones “ program” the brain to be masculine or feminine
(like setting an alarm clock)
•Patterns of behavior as a result of this organization may not appear until adolescence (e.g., sex differences in aggression).
Activating Role:
•Increase in certain hormones at puberty activates physical changes
(e.g., secondary sex characteristics)
What are the affects of hormonal changes of puberty?
. Enters puberty looking like a child; within 4 years or so, has
the physical appearance of a young adult.
. Average individual grows about 10 inches taller, matures sexually,
and develops an adult proportioned body.
. Brain changes in size, structure, and function at puberty.
Adolescent Growth Spurt
The dramatic increase in height and weight that occurs during puberty.
Peak Height Velocity
The point at when the adolescent is growing
most rapidly.
. Girls - 3.5 in per year
. Boys - 4.1 in per year
Epiphysis
The closing if the ends of the bones which terminates growth after the adolescents growth spurt has been completed.
What is the body dissatisfaction among adolescents?
. Increase in height is accompanied by increase in weight, which results
from an increase in both muscle and fat.
. End of puberty: boys’ muscle to fat ratio is 3 to 1; girls’ ratio is 5 to 4
. Rapid gain in fat frequently prompts girls to become overly concerned
about their weight.
. Girls most susceptible to feelings of body dissatisfaction with their bodies are those who mature early and begin dating early.
. Boys’ feeling about their looks revolve around how muscular they are.
Secondary Sexual Characteristics
The manifestations of sexual maturity at puberty, including the development of breasts, the growth of facial and boy hair, and changes in the voice.
Tanner Stages
Widely used system that describes the five stages of pubertal development.
Tanner Stages for a male
Stage 1: infantile stage, birth-puberty, genitalia increase slightly, no pubic hair.
Stage 2: scrotum begins to enlarge, some reddening & change in scrotal skin texture, sparse growth of light hair.
Stage 3: penis has increased in length & small increase in breadth, further growth of scrotum, public hair spreads and is more coarse & dark.
Stage 4: length & breadth of penis increased, scrotum further enlarger & scrotal skin is darker, hair is adult in character but smaller area.
Stage 5: genitalia adult in size, hair fully grown to a triangle.
Tanner Stages for a female
Stage 1: no breast development, no public hair.
Stage 2: breast budding, small amount of public hair along vaginal lips.
Stage 3: breast more distinct, no separation between the two, hair is darker/coarser.
Stage 4: breast further enlarged, greater contour, nipple/areola forms second mound, hair now adult in type but covers a smaller area.
Stage 5: breast fully developed (size varies), contours distinct & areola receded into contour of breast, hair now adult in type & distributed in an inverse triangle.
What is the variation in time & tempo of puberty?
There is no specific average age at onset or duration of puberty.
There is no relation between the age at which puberty begins and the rate of pubertal development. Ethnic differences exist in the timing and rate of pubertal maturation:
•Black mature females (1st); Mexican American females (2nd); White
females (3rd).
•Difference is probably not due to ethnic differences in income, weight,
or area of residence.
•Non White girls may be exposed more often to chemicals that stimulate earlier puberty.
Genetic Disposition of Puberty Timing
Genetic disposition is best thought of as an upper and lower age limit, not a fixed absolute.
Environmental influences on puberty timing
Two key environmental influences exist: nutrition and health.
•Puberty occurs earlier among those who are better nourished..
•Delayed puberty is more likely among individuals with a history of protein and/or caloric deficiency.
•Chronic illness and excessive exercise also linked with delayed puberty.
Familial Influences on Puberty Timing
Early pubertal maturation in girls is related to several factors:
•Father absent families, conflict ridden households, having a stepfather,
and sexual abuse
•Tension in the family and stress, which affects hormonal secretion
•The presence of a stepfather, which may expose the adolescent girl to
pheromones that stimulate pubertal maturation
•Pheromones : A class of chemicals secreted by animals that stimulate certain behaviors in other members of the species.
Differences in timing of puberty in different groups
-Across countries, age at menarche occurs later when malnourished or
suffering from chronic disease
-Median age range of menarche in Africa is 14 to 17; in United States it
is 12 to 13 ½.
The Secular Trend
The tendency, over the past two centuries, for
individuals to be larger in stature and to reach puberty earlier, primarily
because of improvements in health and nutrition.
Immediate impacts of puberty
Physical changes of puberty affect self image, mood, and relationships.
. Puberty and self esteem:
- Impacts of puberty on self esteem varies bu gender and ethnicity.
- White girls are particularly likely to develop poor body images.
. Puberty and adolescent Moodiness:
- More fluctuations throughout the day than adults.
- Not solely due to hormones.
- Greatly influenced by environmental factors, such as shifts in activites.
Changes in sleep patterns during puberty
- Delayed phase preference: A pattern of sleep characterized by later sleep and wake times, which usually emerges during puberty.
- Caused by interaction of biology and environment
- One of most important factors: timing of secretion of melatonin shifts later.
- Environmental factors: Internet, television, electronic media.
- Provide reason to stay up.
- Early school schedule contributes to sleep deprivation.
What does insufficient sleep lead to during adolescence?
- Depression
- Alcohol, tobacco, drug use
- Obesity
- Cognitive impairment
- Delinquency
How does puberty affect family relationships?
Puberty increases conflict and distance between parents and children, regardless of whether adolescent is early or late maturer.
Distancing effect is not consistently observed in ethnic minority families.
Research is inconclusive but increased conflict/distance could be due to changes in various changes in adolescents’ lives:
•Hormones
•Physical appearance
•Psychological functioning
American majority culture: Relations become cooler, Conflict increases, Physical closeness less likely
Traditional cultures: Girls often grow closer to mothers.
How does puberty affect peer relationships?
Physically mature male and female adolescents are more likely than their less mature peers to be involved in cross sex romantic activities.
•Depends on social norms of peer group.
•Also depends on prevailing expectations about dating age
•Not associated with having platonic relationships with other sex peers.
What is the impact of puberty events on females?
Reactions to menarche are less negative than in the past.
- May be attributable more information provided about menstruation.
- Link between negative attitudes and menstrual discomfort.
Modern Day America: Feel more “grown up” increases in social maturity, prestige with peers.
Other Cultures: Girls provided little to no information. fear and dismay, some cultures have negative beliefs about menstruating.
Premenstrual Syndrome (PMS).
What is the impact of puberty events on males?
Less is known about boys’ reactions to first ejaculations.
•Usually not discussed by boys.
•Link between cultural. differences in response to first ejaculation and
views of masturbation.
•Enjoy the pleasurable sensations of it.
•Feel more grown up.
•Guilt, surprise, fear.
•Rarely get info from parents prior to experience.
What is the impact of early or late maturation?
Adolescent are aware of whether they are early or late relative to
classmates.
•Their feelings about themselves are influenced by comparisons
•Early maturers are likely to be “pseudomature.”
Perception of being an early or late maturer is more important in
affecting one’ s feelings than the reality.
Behavior is more closely related to how old the adolescent feels, not
necessarily how physically mature he or she is.
What are the effects of early & late maturation in males?
Early Maturation: •Popularity, achieve greater success.
•Better self esteem.
•More favorable body image
•More drug and alcohol use, delinquency, precocious sexual activity.
•Greater impact of victimization/being bullied.
•Possibly elevated rates of depression and anxiety.
•More intense temper tantrums and depression during puberty.
Late Maturation:
•lower school grades
•substance use, deviant behaviour into early adulthood.
How does puberty influence obesity & eating disorders?
Weight gain sometimes results directly from physical changes of puberty.
•Basal metabolism rate : the minimal amount of energy used by the body when resting.
•It drops about 15% in adolescence.
•Normal weight gain and changes in body composition lead many adolescents to become concerned about weight.
What is BMI
Body mass index (BMI) BMI): A measure of an individual’s body fat, the ratio of weight to height, used to gauge overweight and obesity.
What are the correlates and consequences of obesity?
Correlates and Consequences of Obesity
•Interplay of genetic and environmental factors
•Neurological factors: greater activation of reward centers, heightened
responses to food, poorer impulse control
•Too much high calorie, low fiber food
•Low activity levels
Obesity is especially prevalent among poor youth and among Black,Latino, and Native American adolescents.
Psychological consequences vary across ethnic groups and gender.
Disordered Eating
Mild, moderate, or severe disturbance in eating
habits and attitudes.
Anorexia Nervosa
Anorexia nervosa : An eating disorder found chiefly among young women, characterized by dramatic and severe self induced weight loss.
- 1% of women, 3 times as common in females as in males.
Bulimia
Bulimia An eating disorder found primarily among young women, characterized by a pattern of binge eating and extreme weight loss measures, including self induced vomiting.
- 1.5% of women, 3 times as common in females as in males.
Binge Eating Disorder
Binge eating disorder : An eating disorder characterized by a pattern of binge eating that is not accompanied by drastic attempts to lose weight.
- 3% of women.
How can obesity be prevented and treated?
- Much attention focuses on availability of unhealthy foods and beverages in homes and school.
•Obesity is less likely to develop among adolescents who have good relationships with their parents.
•Availability of parks and recreational facilities is linked to lower rates of obesity.
•Although some weight loss programs have been shown to work, there is wide variability in success rates.
What is the prevalence of eating disorders?
Anorexia
•Observed all over the world
•Increased in prevalence over time.
•Consistent level of heritability across cultures.
Bulimia •Observed mainly in Western cultures. •Increased between 1970 and 1990 but has declined since (parallels levels of body dissatisfaction). •More culturally determined.
Eating disorders are best understood as manifestations of a more general psychological problem called “internalized distress.”
How do the hormones in the feedback loop of the endocrine system function and initiate puberty?
- Hormonal changes begin in hypothalamus.
- Gonadotropin releasing hormone (GnRH) begins at puberty.
- Increased GnRH occurs once a threshold level of body fat is
reached. - Fat cells produce the protein leptin that provides the signal to release GnRH.
- Gonadotropins release once GnRH reaches the pituitary gland.
What are the male and female gonads/sex glands?
Ovaries (female)
Testes (male)
Sex Hormones
Estrogens - most important is estradiol.
Androgens - most important is testosterone.
What does the Adrenocorticotropic Hormone (ACTH) do?
Causes the adrenal glands to increase androgen production.
Primary Sex Characteristics for females
- Egg production.
- Menarche is first menstrual period.
- Ovum is a mature egg, released every 28 days or so, females release about 400 over their lives.
- Changes prepare body for sexual reproduction.
- Female releases an ovum with each monthly cycle.
- Female doesn’t start ovulating at first menstruation.
Primary Sex Characteristics for Males
- Sperm production.
- Spermarche is first production of sperm.
- 30-500 million sperm per ejaculation.
- Changes prepare body for sexual reproduction.
- Male penis and testes grow.
Secondary Sex Characteristics for females
Bodily changes that are not directly related to reproduction.
- Hair growth in pubic areas, under arms, face.
- Hairiness on arms and legs increases.
- Sweat glands in the skin increase production.
- Females experience breast growth.
Secondary Sex Characteristics for males
Bodily changes that are not directly related to reproduction.
- Hair growth in pubic areas, under arms, face.
- Hairiness on arms and legs increases.
- Sweat glands in the skin increase production.
- Deepening of the voice
- Males grow hair on chests, shoulder, and back.
What is the female order of pubertal events?
- Pubic hair
- Breast buds
- Growth spurt
- Growth of sexual and reproductive organs.
- Menarche
- Underarm hair
- Secretion of increased skin oil and sweat.
What is the male order of pubertal events?
- Pubic hair growth
- Growth spurt
- Growth of penis
- Deepening of the voice
- Spermarche
- Underarm hair
- Secretion of increased skin oil and sweat.
- Facial hair
What are the changes in physical functioning in relation to heart, lungs, physical performance, bone mass, oxygen uptake, and cardiac output during puberty?
17 average girls is 5 beats faster than the average boys.
. Lung vital capacity (amount of air that can be exhaled after a deep breath) increases rapidly (more boys than girls).
- Boys overtake girls in physical strength.
- For most people, the peak of their physical functioning comes during emerging adulthood.
- Reaction times fastest in 20s.
- Peak bone mass reached in the 20’s.
- Maximum oxygen uptake, peaks in early 20s.
- Cardiac output, peaks at age 25.
What are the changes in physical functioning in relation to weight during puberty?
Obesity: Exceeding a specific body mass index (BMI).
- About 20% of American adolescents are obese.
–Diet and exercise major cause: fast food diet, American lifestyle more automobile oriented, steep decline in physical activity from middle childhood to
adolescence, soft drink and junk food machines in schools.
How does culture influence the timing of puberty?
- Puberty begins earlier in cultures where good nutrition and medical care are widely
available. - Secular trend - Age of menarche decreasing.
- Within countries, adolescent girls from affluent families menstruate earlier than
girls from poorer families. - Reaction range genes establish a range of possible development and environment determines where it takes place within that range.
What are cultural responses to puberty?
- Majority of cultures have some kind of ritual initiation into adolescence.
- Menarche often initiates a monthly ritual that lasts throughout a woman’s reproductive life.
- Puberty rituals for males do not focus on a particular biological event. Typically require the young man to display courage, strength, and endurance. Often violent. Seen as necessary to face life’s challenges as a man.
3 genotypes and their environmental effects?
Passive genotype - environmental effects: Difficult to separate genetic and environmental influences
because parents provide both. Strong in early childhood, diminishes during adolescence.
Evocative Genotype - environmental effects: Person’s inherited characteristics evoke responses from others
in their environment, –
effects remain stable from childhood through adulthood.
Active Genotype - environmental effects: People seek out environments that correspond to their
genotypic characteristics. Minimal during early childhood, Increases during adolescence.
Feedback loop?
A cycle which 2 or more bodily functions respond too and regulate each other.
Set Point
A physiological level or setting that the body attempts to maintain through a self-regulating system.
Hypothalamus
Part of the brain that controls the pituitary gland.
Pituitary gland?
One of the chief glands responsible for regulating levels of hormones in the body.
Gonads
Glands that secrete sex hormones (male-testes) (female-ovaries).
