Lecture 10a: Physical and Brain Development in Adolescence

Question 1

What happens to grey and white matter during middle childhood?

Answer 1

During middle childhood, developments in the brain include changes to white and gray matter volume, growth in the complexity of neural networks, and increased coordination across regions of the brain.

Question 2

What happens to white matter?

Answer 2

White matter volume increases linearly throughout middle childhood and adolescence, reflecting the myelination of axons

Recall that myelin is the fatty white sheath that surrounds axons.

The growth in myelin helps strengthen brain connections by allowing faster transmission of neural signals.

Question 3

What happens to grey matter?

Answer 3

Grey matter increases in childhood and then decreases in adolescence, reflecting the pruning of unused synapses.

Peaks to gray matter volume occur in different regions of the brain at different times in development.

Question 4

How can we appreciate adolescent thinking?

Answer 4

To fully appreciate adolescent thinking and decision making, it’s helpful to consider the asymmetrical maturity of different brain regions across development. Notably, by adolescence, the prefrontal cortex is relatively immature in its development compared to the more complete maturation of the limbic system

Question 5

What is the limbic system?

Answer 5

The highly active adolescent limbic system which includes the hippocampus, amygdala, and cingulate gyrus, among other structures is packed with neurons that are involved in motivation and emotions.

Simplified; The limbic system is a group of interconnected brain structures that help regulate your emotions and behavior

Question 6

What is Puberty?

Answer 6

Period of lifespan in which individual becomes capable of sexual reproduction

Question 7

What are the 3 chief physical manifestations?

Answer 7

• Rapid acceleration in growth (height, weight)
• Development of primary sex characteristics (gonads)
• Development of secondary sex characteristics

Question 8

What is the Endocrine System

Answer 8

Produces, circulates, and regulates hormone levels in the body

• Hormones
• Glands
• Gonadotropin-releasing hormone (GnRH) neurons

Question 9

What is the Hypothalamic-Pituitary-Gonads “HPG Axis”

Answer 9

Reproduction and fertility are regulated via hormones of the hypothalamic-pituitary-gonadal (HPG) axis.

**Controls production of
androgens and estrogens by
gonads

REVIEW SLIDE 8 CHART

Question 10

What are Primary sex characteristics

Answer 10

Primary sex characteristics are associated with the reproductive organs, ovaries, uterus, and vagina in girls, and penis, scrotum, and testes in boys.

Primary sex changes result in the production of ova in girls and sperm in boys, which enable reproduction.

Question 11

What are secondary sex characteristics?

Answer 11

Secondary sex characteristics include observable body changes such as a growth spurt, pubic hair, breasts in girls, and facial hair and changes to voice in boys.

Question 12

What Triggers Puberty?

Answer 12

Puberty begins when several different signals – genetic, environmental – instruct the brain to change the “set
point” of the HPG axis

Question 13

What signals the HPG axis to change the set point?

Answer 13

Increase in brain chemical called “kisspeptin” – initiates increased
secretion of GnRH from hypothalamus

[Gonadotropin hormone-releasing hormone (GnRH)]

Hypothalamus becomes less sensitive to androgens/estrogens

Question 14

What products kisspeptin?

Answer 14

Leptin (protein produced by fat cells) stimulates production of kisspeptin

Question 15

What are the 3 chief physical changes during Somatic Development?

Answer 15

• Adolescent growth spurt
• Development of primary sex characteristics (gonads)
• Development of secondary sex characteristics (breasts, body hair)

Question 16

What is growth spurt?

Answer 16

One of the most noticeable outcomes of puberty is the growth spurt acceleration of growth in hands, legs, and feet followed by torso length

Question 17

How do boys and girls differ in growth spurt?

Answer 17

Boys’ shoulders broaden relative to their hips, but girls’ hips broaden relative to their shoulders.

Girls also add fat to their limbs and torso, whereas boys reduce fat and add more muscle mass to their bodies than do girls

Moreover, the growth spurt occurs at a later age and lasts longer in boys than in girls. Thus, during middle school and the first year or two of high school, it is common to see girls towering over boys, with this pattern reversing a couple of years later.

Question 18

What are the Sex Differences in Muscle and Fat?

Answer 18

Relative proportions of body fat/muscle change during puberty

Muscle-to-fat ratio at end of puberty is 3:1 (boys) vs. 5:4 (girls)

Question 19

What is the timing of puberty for girls

Answer 19

Secondary sex characteristics: 10 years old on average

First period: 12-13 years old on average

Question 20

What is the timing of puberty for men

Answer 20

Secondary sex characteristics: 11-11.5 years old on average

Question 21

What are Secular trends?

Answer 21

Secular trends are nongenetic changes in human development that occur over extended time frames, further illustrate diet’s effect on pubertal timing. Worldwide improvements in nutrition and health over centuries have led to earlier and earlier onsets of puberty

Question 22

What are the Individual Differences in Pubertal Timing?

Answer 22

• Genetic predispositions

Two key environmental influences:
* Nutrition
* Health

Protein/caloric deficiency, chronic illness, intensive exercise = Delayed puberty

Question 23

What is ehe role of the pituitary gland in puberty?

Answer 23

The hypothalamus increases production of gonadotropin-releasing hormone, which stimulates the pituitary gland to release gonadotropin hormones, which trigger the production of testosterone and estrogen. The release of testosterone and estrogen from the pituitary gland causes a series of chemical changes that trigger the physical transformations of puberty

Question 24

What does early maturation feel like for girls?

Answer 24

In general, early pubertal timing relative to peers may render adolescents susceptible to depression and behavior problems, although such negative effects have been most consistently documented for female adolescents

Question 25

What does late maturation feel like for girls?

Answer 25

Adolescents who show asynchronous development in the physical changes associated with puberty, such as developing breasts very late are at greater risk of depressive symptoms at age 20

Question 26

What are the Mechanisms of Influence on puberty? AKA Why does the timing of puberty relative to one’s peers matter?

Answer 26

1. Peer influence hypothesis
2. Maturational deviance hypothesis
3. Readiness hypothesis
4. Contextual amplification hypothesis

Question 27

What is peer influence hypothesis?

Answer 27

Early puberty may instigate problem behaviors because of the influence of older peers.

Early maturing adolescents are likely to hang out with older teens who look like them physically. They are thus prone to earlier-than-usual exposure to risky behaviors, such as alcohol use and sexual activity, at a time when they are insufficiently mature to handle peer influences

Simplified: Influence of older peers

Question 28

What is Maturational deviance hypothesis?

Answer 28

The adolescent’s physical deviation from his or her peer group, whether due to early or late maturation, is stressful and may increase vulnerability for mood and behavior problems.

Early maturing girls are the most physically “deviant” because they enter puberty before most other girls their age and before nearly all boys their age.

In contrast, late-maturing boys are the most physically “deviant” because they are the last to develop relative to boys and girls of their age

Simplified: Stress caused by being different from peers

Question 29

What is Readiness hypothesis?

Answer 29

That early maturation may be problematic because of the asynchrony it creates between physical, cognitive, social, and emotional maturity

Question 30

What is Contextual amplification hypothesis?

Answer 30

Adolescent adjustment to early pubertal timing, especially in girls, depends on social and cultural context.

Social messages about sexuality and body image interact with a teen’s experience of puberty to determine whether and to what degree early timing cascades to problem behaviors

Question 31

How does the Home Context affect Puberty?

Answer 31

Environmental forces, such as social interactions in the family and foods available at home, also contribute.

Adolescents who experience prolonged, unpleasant conditions at home, including conflict and stress among family members, parental divorce, poor attachment relationships, child maltreatment, and low parental involvement, are prone to early pubertal onset