Biological Transitions - Puberty Flashcards
What is puberty?
The period during which an individual becomes capable of sexual reproduction
- Females start menstruating and males start being able to ejaculate sperm
What are 3 pre-through-post-pubertal changes that adolescence go through?
- Biological
- Cognitive
- Social
What 2 systems of the brain are the changes being driven by?
The Endocrine system
The Central Nervous System
What does the onset of puberty depend on?
Hormones
What are organizational effects?
The prenatal effects of hormones causing differentiation and organization of physiological systems
- Your brain is being altered by hormones before you’re even born - exposed to in utero
What are the activational effects?
The effects of hormones upon these previously organized systems
What are the critical hormones?
- Androgens - Testosterone
- Estrogen and progesterone
Do both males and females produce both types of hormones?
Yes, but the quantity is dfferent
Is there a critical period during development when hormones have an organizational effect on both physiology and on brain wiring?
Yes.
- The presence or absence of the appropriate hormones during this critical period determines the appearance and behavior of the adult
True or False: Everyone embryo starts out as Bi-Potential
True.
The embryo could be male or female
Is it the X or Y chromosome that is going to decide if the embryo is going to be a male or female?
The direction an embryo takes is determined by the presence or absence of a Y chromosome
What does the Y chromosome contain?
The Y chromosome contains a tiny little gene called the Sex Determining Region of the Y Chromosome (SRY gene) that is responsible for producing a protein called Testes Determining Factor (TDF)
What is TDF?
Testes Determining Factor
What happens when the SRY gene activates TDF?
the bipotential tissue begins to masculinize and will develop into testes, which produce Androgens (particularly Testosterone) that stimulates the development of the penis
What happens in the absence of the TDF?
the bipotential tissue develops as female sex organs: the ovaries and vagina (Historically, this led some to erroneously conclude that female was the “default” sex)
What is Androgen Insensitivity Syndrome (AIS)?
A genetic male who is resistant to androgens
What is Complete Androgen Insensitivity Syndrome (CAIS)?
the penis and other male body parts fail to develop so that at birth, the child is sexed as female
What is Partial Androgen Insensitivity Syndrome (PAIS)?
may appear with predominantly female, predominantly male, or ambiguous external genitalia
True or False: Most cases of AIS are genetic and inherited from the father
FALSE.
They are genetic but they are inherited from the mother
True or False: AIS males are almost always infertile
TRUE
Can PAIS lead to gender dysphoria?
Yes because the brain has partially masculinized
Are people with AIS typically raised as male or female?
They are typically raised as females
- In CAIS, despite the presence of a Y chromosome, this is fine, masculinization of the brain has not occurred
What is 5-alpha Reductase Deficiency?
Genetic male who develops testes and produces testosterone but is unable to effectively convert Testosterone to the substance required for the proper development of the penis (dihydrotestosterone)
- Often sexed as females at birth
What happens during puberty of individuals who have 5-alpha Reductase Deficiency?
- an increase in Testosterone production leads to the development of typical male sex characteristics
- Gender dysphoria is VERY common in this case because the brain WAS masculinized…
What are the primary sexual characteristics present at birth?
Internal genitalia such as testes and ovaries
External genitalia such as penis and vagina
What are the 3 primary physical changes that occur during puberty due to the activational effects of hormones?
- Further development of Primary Sex Characteristics
-Development of Secondary Sex Characteristics
- Rapid acceleration in growth: The Adolescent “Growth Spurt”
What are the secondary sexual characteristics that emerge during the pubertal phases for males?
Facial hair, muscle growth, pubic hair, body odor
What are the secondary sexual characteristics that emerge during the pubertal phases for females?
Breasts, rounding of hips, pubic hair, body odor
What is the adolescent growth spurt?
The dramatic increase in height and weight that occurs during puberty
- Usually occurs in spurts and during a short amount of time
- Pituitary hormones prompt growth (Adolescent growth spurt)
What is peak height velocity?
The point at which the adolescent is growing most rapidly
What may occur due to the adolescent growth spurt?
Body dissatisfaction
- Increased in height is accompanied by increase in weight
What are boys muscle-to-fat ratio by the end of puberty?
3 to 1
- Boys feelings around their looks revolve around how muscular they are
What are girls muscle-to-fat ratio by the end of puberty?
5 to 4
- Leads girls to become overly concerned about their weight
- Early matures are most susceptible to feelings of body dissatisfaction
What is the timing of the activation effects of hormones dependent on?
The function of the Endocrine System
What does the endocrine system do?
- In general, the endocrine system produces, circulates, and regulates hormone levels in the body
- The levels of sex hormones (i.e., androgens, estrogen) circulating in the body are controlled by a feedback loop
What does the hypothalamus do?
- Monitors levels of sex hormones to maintain the correct set point
- Inhibits the pituitary gland unless sex hormones levels fall below a set point
What is adrenarche?
- The maturation of the adrenal gland that began in middle childhood (we don’t know why) is completed during adolescence
What does adrenarche result in?
Sometimes called the “puberty of the adrenal gland”
– it results in a steady increase in the production of sex hormones (i.e. androgens and estrogens) that result in the development of pubic hair, oily skin, oily hair, and body odor
What is the HPG axis?
The Hypothalamic-Pituitary-Gonadal Axis
What initiates the activations of the HPG axis?
Just before puberty, the pituitary begins to secrete hormones but we don’t know exactly why
- Presence of mature sexual partners
- Sufficient nutritional resources
- Physically healthy enough to begin reproducing
Which chemicals are involved in the activation of the HPG axis?
- Kisspeptin
- Leptin
- Melatonin
What is kisspeptin?
A chemical produced by mature kisseptin neurons, believed to trigger the onset of puberty
What is Leptin?
A brain chemical produced by the fat cells that may play a role in the onset of puberty through stimulating kisspeptin neurons (It’s typical function is to increase appetite!)
What is melatonin?
A hormone secreted by the brain that contributes to sleepiness and that triggers the onset of puberty through its impact on kisspeptin neurons
What are some somatic development because of the effects of hormonal changes during puberty?
- Individual enters puberty looking like a child; shortly thereafter has the physical appearance of a young adult
- The average individual grows about 10 inches taller, matures sexually, and develops an adult proportioned body
- The brain changes in size, structure, and function at puberty
True or False: There is a specific average age at onset and duration of puberty.
FALSE.
There is NO specific average age at onset OR duration of puberty
True or False: There is no relation between the age at which puberty begins and the rate of pubertal development
TRUE
Are there ethnic differences in the time and rate of pubertal maturation?
There ARE ethnic differences in the timing and rate of pubertal maturation:
Black females (1st); Mexican American females (2nd); White females (3rd).
- Difference is probably not due differences in income, weight, or area of residence
- Likely related to environmental (i.e. chemical) and/or genetic factors
Are the timing and tempo of puberty inherited?
Largely inherited
- Genetic disposition is best thought of as an upper and lower age limit, not a fixed absolute
What are two key environmental influences that can cause individual differences in pubertal maturation?
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
Does familial influence have an effect on pubertal timing?
Social factors in the home environment may influence the onset of maturation, especially in girls
- Tension in the family (i.e., absence of father, conflict-ridden households, sexual abuse): All are stressors
- Stressors can directly impact the production of hormones!
- The presence of a stepfather, which may expose the adolescent girl to pheromones that stimulate pubertal maturation
What are pheromones?
A class of chemicals secreted by animals that stimulate certain behaviors in other members of the species.
