Chapter 2: Physical Development Flashcards
Define PUBERTY.
the chances in physiology, anatomy, and physical functioning that develop a person into a mature adult biologically and prepare the body for sexual reproduction
What is the ENDOCRINE SYSTEM?
a network of glands in the body; through hormones, these glands coordinate their functioning and affect the development and functioning of the body
What are HORMONES?
chemicals released by the glands of the endocrine system that affect the development and functioning of the body, including development during puberty
What is the HYPOTHALAMUS?
located in the lower part of the brain beneath the cortex, a gland that affects a wide range of physiological and psychological functioning; also stimulates and regulates the production of hormones by other glands, including those involved in the initiation of puberty
Which hormone is released in increased amounts by the hypothalamus to initiate puberty?
Gonadotropin-Releasing Hormone (GnRH)
How does GnRH function to initiate puberty?
causes gonadotropins to be released by the pituitary gland
When does the increase in GnRH initially begin?
middle childhood, at least a year or 2 before even the earliest bodily changes of puberty
once a threshold level of body fat is reached
What is LEPTIN?
a protein produced by fat cells that signals the hypothalamus to initiate the hormonal changes of puberty
Given the role of fat cells in the onset is puberty, what can we assume about overweight and underweight children, respectively?
Overweight adolescents tend to experience puberty earlier than average weight, and underweight adolescents tend to experience puberty later
What is the PITUITARY GLAND?
a gland about half an inch long located at the base of the brain that releases gonadotropins as part of the body’s preparation for reproduction
What are GONADOTROPINS?
hormones (follicle-stimulating hormone [FSH] and luteinizing hormone [LH]) that stimulate the development of gametes
What are GAMETES?
cells involved in reproduction: eggs in females, sperm in males
Review the SEX HORMONES:
Estrogens > higher in females (8x) > most important in respect to puberty is estradiol
Androgens > higher in males (20x) > most important in respect to puberty is testosterone
What is ADRENOCORTICOTROPIC HORMONE (ACTH)?
at puberty, hormone that is increased in the pituitary gland to increase androgen production > these have the same effects as the androgens released by the testes
What kind of a system is formed by the elements involved in puberty?
a feedback loop
How does the feedback loop of the endocrine system function during puberty?
- The hypothalamus monitors the levels of androgens and estrogens in the bloodstream
- when sex hormones reach their set point (optimal level), the hypothalamus reduces its production of GnRH
- The pituitary gland responds to this reduction by reducing its production of FSH, LH, and ACTH
- The glands and adrenal glands respond to the lower level of FSH and LH by reducing the amount of sex hormones they produce
Describe how the feedback loop resembles a thermostat.
Like a thermostat that is working to maintain a constant temperature despite drops and rises, your body adjusts the production of sex hormones to maintain the set points
What happens to sex hormone set points during puberty?
when puberty begins, the set points for androgens and estrogens rise in the hypothalamus, causing the gonads to increase production until they are told by the hypothalamus to decrease
What is the ADOLESCENT GROWTH SPURT?
rapid increase in height that takes place at the beginning of puberty
What is PEAK HEIGHT VELOCITY?
adolescent growth spurt is at its maximum
girls grow ~ 3.5 inches per year, boys grow ~ 4.1 inches
What sex differences exist in the growth spurt and height velocity measures?
- Girls typically reach the beginning of their growth spurt and peak height velocity about 2 years earlier; this pattern is also present in other aspect of physical development
- Girls become taller on average for about 2 years (ages 11-13), which is likely due to the earlier growth spurt
What is ASYNCHRONICITY of growth?
uneven growth of different parts of the body during puberty
extremities (hands, feet, head) are the first to grow, followed by arms and legs
Which body parts are typically the last to reach the growth spurt and the last to reach the end of growth?
torso, chest, and shoulders
Which body parts widen more in boys and girls, respectively?
shoulders for boys
hips for girls
How does muscle mass and body fat growth differ between the sexes?
boys experience greater testosterone levels and so also experience a greater increase in muscle growth > at the end of puberty, boys have a muscle-to-fat ratio of ~ 3:1
girls experience a greater increase in body fat due to increase in estradiol > at the end of puberty, girls have a muscle-to-fat ratio of 5:4
Define PRIMARY SEX CHARACTERISTICS.
the production of eggs and sperm and the development of sex organs
Describe the nature of egg production in females.
females are born with about 2 million immature eggs; by puberty, this number has declined to ~ 200,000
once menarche is reached, one egg develops into a mature egg (OVUM) every 28 days or so
females release ~ 400 ovum over the course of their reproductive lives
What is SPERMARCHE?
first production of sperm in boys at puberty, at ~ age 12
Describe the nature of sperm production in males.
once it begins, sperm production occurs in large quantities: there are bw 100 and 300 million sperm in the typical male ejaculate, so the average male is producing millions of sperm per day
Why is it necessary for males to produce sperm in such large quanities?
the environment of the female body is not hospitable to sperm, and the sperm have a long way to travel to reach the ovum > having lots of them make their way at once increases the likelihood that some of them will be able to fertilize
Describe changes to female sex organs during puberty.
external sex organs all grow in size
ovaries increase greatly in size and weight, reflecting the growth of maturing ova
the uterus doubles in length to about 3 inches
vagina increases in length and deepens in colour
menarche arrives
Describe the changes to the male sex organs during puberty.
the penis doubles in length and diameter
the testes increase 2.5x in length and 8.5x in weight, reflecting the production of many millions of sperm
What is the nature of ovulation once menarche arrives?
the majority of girls’ menstrual cycles in the first 2 years do not include ovulation; the 3rd and 4th years only about 1/3-1/2 of cycles include ovulation
consistent ovulation will occur after about 4 years
What are SECONDARY SEX CHARACTERISTICS?
bodily changes of puberty not directly related to reproduction
What secondary sex characteristics typically occur for both sexes?
hair growth in pubic area and underarms
facial hair growth (more pronounced in males)
hair on the arms and legs (more pronounced males, who may also grow hair on the shoulders, chest, and back)
sweat glands increase production, resulting in stronger body odor and oilier skin more prone to acne (86% prevalence)
deepening of voice as vocal cords lengthen (more so in males)
Describe the nature of breast development during puberty.
Both males and females will experience some growth in this area; about 1/4 of boys will see growth that recedes after about 1 year
girls will experience the development of BREAST BUDS and enlargement of the AREOLA, which will eventually recede and leave the nipple protruding
What is the typical age of onset for puberty?
among young people in developed countries, first pubertal events may occur as early as age 7 in girls, age 9-10 in boys, and as late as age 13
What is the typical duration of puberty?
the duration bw the initiation of the first event and full maturation can be as short as 1.5 years and as long as 6 years
age alone is a poor predictor of an adolescent’s puberty development
What is the typically consistent pattern of pubertal events in females?
Downy pubic hair > development of breast buds > growth spurt, growth of sexual and reproductive organs > menarche, underarm hair, secretion of increased skin oil and sweat
What is the typically consistent pattern of pubertal events in males?
growth of the testes > beginning of pubic hair > growth spurt, increased growth of penis, deepening of voice > growth of underarm hair and secretion of oil and sweat > facial hair growth (usually ~ 2 years after first outward events)
What are some cultural variations we are aware of in puberty?
- In Kikuyu culture in Kenya, boys show first physical changes in puberty before girls, a reversal of Western patterns
- Most Chinese girls demonstrate public hair growth 2 years after the development of breast buds, and very shortly before menarche
- Many American Black girls were found to develop breast buds and pubic hair earlier than White girls
What do we know about the relationship bw genetics and the order/timing of pubertal events?
Identical twins, being the most similar genetically, tend to be the most similar in the timing of pubertal events, so we can assume these qualities are at least somewhat due to genetics, but environment very clearly has an impact as well
What happens to the heart in both boys and girls during puberty?
weight almost doubles, on average, and heart rate falls
by 17, the average girl’s heart rate is about 5 BPM faster than the average boy’s
What is VITAL CAPACITY?
the amount of air that can be exhaled after a deep breath
increases rapidly during puberty, especially for boys
How do sex differences in physical growth and functioning affect strength and athletic ability?
before puberty, boys and girls are about equal in strength and athletic performance
during puberty, boys overtake girls and the difference remains through adulthood
What are some of the reasons that overweight and obesity are impacting the adolescent population?
adolescents are consuming more calories, portions have increased, fast food frequency has increased
physical activity is declining, showing a steep decline in physical activity from middle childhood to adolescence
media consumption and time
genetics, and possible interaction bw genes and environment
What is the nature of the suspected gene-environment interaction regarding BMI for contemporary adolescents?
people with a common variant of the gene FTO tend to have a higher BMI, but only in those born after 1950
the more recently those with the variant were born, the more likely they are to be overweight/obese
we don’t know yet which environmental factor could be related
What elements are a part of a successful program to address and reverse overweight/obese in adolescence?
nutrition education
dietary assessment
modifications of meals provided in schools
efforts to increase physical activity
What is MAXIMAL OXYGEN UPTAKE?
a measure of the ability of the body to take in oxygen and transport it to various organs; peaks in the early 20s (emerging adulthood)
What is CARDIAC OUTPUT?
quantity of blood flow from the heart; peaks at age 25
What is generally the nature of people’s health in the emerging adulthood stage?
for most people, the peak of health and strength, period of the lifespan with the least susceptibility to physical illness > no longer vulnerable to diseases of childhood and not yet typically vulnerable to diseases of old age
What elements of behaviour can undermine health of emerging adults?
Poor nutrition
Lack of sleep
High stress of school/work
Decline of physical activity, sports participation and exercise
Car accidents, homicide, STIs, substance use/abuse
What are some features of sleep in adolescence and emerging adulthood?
sudden changes can occur in adolescence, including timing of sleep, sleepiness, and composition of sleep and wake brain waves
we typically see a shift toward “eveningness” where teens and young adults are up later and sleep later > the tendency for “morningness” increases after the age of 20
What are some of the negative consequence of poor sleep in adolescence?
high school students with lower sleep time have higher levels of perceived stress, report mood disturbances, suicidal ideation, unhappiness, school absence due to illness, and fatigue
poor sleepers are 2x more likely to fail a year of school; GPAs are better among college students with regular sleep habits and who sleep longer
What is HEALTH PROMOTION?
efforts to reduce health problems in young people through encouraging changes in the behaviours that put young people at risk
How do cultural elements influence the timing of puberty?
age at which puberty begins is strongly influenced by the extent to which food production provides for nutrition and medical care provides for good childhood health
generally, puberty begins earlier in cultures where good nutrition and medical care are widely available
What is a SECULAR TREND?
a change in the characteristics of a population over time
Describe the secular trend we are seeing regarding menarche in Western countries.
Over the last 150 years, there has been a steady decrease in the average age of menarche.
Scholars believe this is due to improvements in nutrition and medical care; medical advances have reduced illnesses; food production advances have enhanced nutrition.
Why is menarche considered a good overall marker for the onset of puberty, for research purposes?
though it is not perfect, is generally reflects when other pubertal events have begun
it is the only aspect of pubertal development for which we have such long historical records
easy to identify when menarche itself begins
What is REACTION RANGE?
the genes that establish a range of possible development and environment determines where development takes place within that range
Why is reaction range relevant to the secular trend of menarche age decreasing?
despite the overall decreasing trend, the decline has slowed, suggesting that the reaction range of menarche has boundaries: even under relatively unhealthy conditions, most girls will eventually reach menarche, and in the healthiest conditions, there is a lower boundary that menarche is unlikely to fall below
What other pubertal growth area is seeing a decrease in age of onset, and why is it occuring?
breast development among girls now begins by age 7 for up to 1/4 of girls
cause could be related to increase in obesity rates, as puberty is related to increase in body fat
possible role of endocrine disruptors in plastics or additives to milk
What are some common cultural beliefs around menarche and menstrual blood?
Negative beliefs: danger to growth and life of crops, health of livestock, success of hunters, well-being of other people, especially husbands
Positive beliefs: promoting fertility, used in rituals, treatment of medical conditions, to make potions
Describe the experience of menstruating Asante women in Ghana.
women are subject to numerous regulations concerning where they can go and what they can do, and the penalty for violation can be death
however menarche is celebrated with an elaborate ritual ceremony where the girl sits publicly and is celebrated
What is MIKVEH?
a ritual bath that Orthodox Jewish women are given 1 week after their period as a way of cleansing themselves
many Orthodox Jewish women report that this ritual makes them feel more connected to other Jewish women
What is the nature of rituals associated with boys’ puberty and maturation?
not typically associated with a particular biological event
young men must display courage, strength, endurance > rituals let them know what will be required of them as adult men, test their ability to meet life’s challenges
How do parent and child relations change upon onset of adolescents in the West?
relations tend to become cooler, conflict increases and closeness decreases, especially physical closeness
if the child reaches puberty early, these changes will happen earlier, and vice versa
How do many 10-15 year olds feel towards their mothers and fathers, respectively?
regardless of age, those who had reached puberty felt less close to their mothers, and less accepted by their fathers
What is the INCEST TABOO?
the prohibition on sexual relations between family members; believed to be biologically based bc children born to closely related parents are at higher risk for genetic disorders
Why is the incest taboo not necessarily a satisfactory answer for why parent/child relations cool in adolescence?
one would expect to find distancing between parents and adolescents in all cultures, but this is not the case > mainly occurs in 2-parent White American families
in nearly all cultures, adolescents of both sexes tend to be closer to mothers than fathers > incest taboo suggests that boys should get closer to fathers
How do girls typically report feeling about the arrival of their menstrual cycle?
typically positive > makes them feel “more grown up,” allows them to catch up to peers who have already been menstruating
over time, menarche is followed by increases in social maturity, prestige with peers, and self-esteem
What factors might cause a girl to have a negative experience of menarche?
some cultures provide girls with no information to help them anticipate it, or with a view that leads them to anticipate it negatively
girls in developing countries consistently demonstrate limited knowledge and more negative emotions once their period arrived
What is the prevalence of PMS and what is the most common symptom?
50-75% of girls experience physical discomfort approaching or during their period
30-50% of girls and women report cramps
How does availability of sanitary products affect women and girls in developing countries?
lack of availability is associated with school absenteeism, with significant numbers of girls missing school during their period in countries like Nepal and Uganda
What is SEMENARCHE?
first ejaculation for boys
What are boys’ general reactions to semenarche?
though there is very little research on this topic, the boys that have been surveys have indicated enjoyment of pleasurable sensations, feeling more grown up, but also some reports of guilt, surprise, or fear
How do cultures influence boys’ experience of semenarche?
semenarche most commonly occurs during a “wet dream” or masturbation, both of which are shamed and censored in Western society, leading many boys not to tell anyone once they experience it
How does age-grading of Western classrooms affect students going through puberty?
adolescents seem to be acutely aware of whether they have reached puberty early or late, compared to their peers; intensifies comparisons
How does age factor into puberty rites in traditional cultures?
It doesn’t - eligibility for puberty rites is based only on pubertal maturation, including for boys > the adults of the community will decide when a boy is ready based on his physical maturation and their perceptions of his mental and social readiness
What are the effects of early maturation for girls?
typically negative > at risk for depressed mood, negative body image, eating disorders, substance use, delinquency, aggressive behaviour, school problems, and conflict with parents
What is a possible reason for the negative effects of early maturation for girls?
cultural values about physical appearance: early maturation typically leads to a shorter and heavier appearance, which is a disadvantage in Western cultures that value thinness > most prevalent among White Western girls
Why might early maturing girls be at higher risk for delinquent behaviour, substance use, etc?
may draw the attention of older males, who may introduce them to an older friend group which may include these activities
What do studies find regarding the long-term effects of early maturation?
typically, negative effects diminish by the late teens; some studies have also found that early maturing girls enter marriage and parenthood earlier than late maturing girls, possibly more psychological and social problems in their 20s
What is the general experience of early maturing boys?
tend to have more favourable body image, be more popular, possibly due to early growth and muscular development
also tend to be more involved in delinquency, sex and substance use earlier, possible higher rates of emotional distress and depressive symptoms
What features are often found for late maturing boys?
higher rate of alcohol use and delinquency; lower grades in school; possibly elevated substance use and deviant behaviour into adulthood
What are the 3 types of genotype > environment effects?
Passive
Evocative
Active
What is a PASSIVE GENOTYPE > ENVIRONMENT EFFECT?
situation in biological families where parents provide both genes and environment to their children, making genes and environment hard to separate in their effects on child development
Give an example of a passive genotype > environment effect.
An artistic parent provides a home environment that nurtures their child’s artistic interest and skills, and their child demonstrates strength in this area
What is an EVOCATIVE GENOTYPE > ENVIRONMENT EFFECT?
situation in which a person’s inherited characteristics evoke responses from others in the environment
others will react differently to people depending on characteristics and related behaviour
What is an ACTIVE GENOTYPE > ENVIRONMENT EFFECT?
situation in which people seek out environments that correspond with their genotypic characteristics
people are drawn to environments that match their inherited abilities
Why are passive effects more prominent in childhood, and active effects relatively weak?
parents are in the most control of young children’s experiences, and young children don’t have as many opportunities to actively seek out environments
How does the prevalence of passive and active effects change throughout the lifespan?
passive effects will decrease and active effects will increase as adolescents and emerging adults gain more agency
evocative effects tend to remain stable
How do we see the reverse relationship (environment > genes) emerge during puberty?
when girls’ environmental conditions change, their menstrual patterns may also change
EX: weight loss can stop menstruation, weight regain can start it again
