Ch 5: Sex Hormones, Sexual Differentiation, and the Menstrual Cycle

Hormones

(Reproductive) chemicals

• produced by endocrine glands

Top three sex hormones:

1. Testosterone

2. Estrogens

3. Progesterone

Which hormone is an androgen?

testosterone

What hormone(s) are generally associated with males and produced mainly in the testes?

Testosterone

- Testes Testosterone

Role of testosterone in sex

1. sperm production

2. involved in sexual drive/arousal (but not soley responsible)

3. secondary sex characteristics

4. bone and muscle growth

T or F: Women have testosterone

True.

- It is just more dominant in males

What hormones are mainly produced in the ovaries and are associated mainly with women?

Estrogen and Progesterone

Role of Estrogen

• puberty — developmental and phenotypic sex characteristics

• maintains mucous membranes of vagina

• stops growth of bone and muscles in females

Levels of ______ and _______ fluctuate according to the phases of the menstrual cycle, pregnancy, and menopause

estrogen and progesterone

Epigenetics

the study of changes in gene expression that occur without altering the DNA sequence

Sex Chromosomes in Prenatal development

sex chromosomes are carried in a fertilized egg

XX vs XY

XX are female

XY are male

How many weeks after conception are basic reproductive structures formed in the embryo?

the 7th week

Prenatal gender differentiation of brain

The brain

• No significant differences

  • Women use both sides of brain

  • Women’s frontal lobe develops quicker

• Plasticity is emphasized

  • brain is constantly evolving, being shaped by experiences

Intersex

Individuals born with several sex characteristics that do not fit typical binary of men and women

→ consequence: both male and female reproductive organs are present

• typically it is unclear whether the individual is male or female at birth

What was the term “Intersex” referred to before it got its name?

Hermaphadite

Adolescence is a _____ construct

social construct

What is an example that illustrates puberty is biologically marked, and adolescence/adulthood is socially marked

It is a transitional phase

• time during which there is a sudden enlargement and maturation of the gonads, other genitalia, and secondary sex characteristics, so that the individual becomes capable of reproduction.

Social markers of adolescence/womanhood

Having your first period → entering adolescence

Graduating high school/joining the military → transitioning into womanhood (from adolescence)

Adolescence

A socially defined period that relates to puberty

• Does not exist in all cultures

When does puberty end?

Currently, the answer is unknown.

Phenotypic signs of puberty in women

• breast development

• pubic hair

• become curvier

What age does puberty begin for women?

average = 8/9 years old

What hormone stops growth spurt in women? And what are the consequences of this?

Estrogen

• explains why women aren’t as tall as men

  • → girls get growth spurt earlier than boys do

Who matures faster: girls or boys

girls

Who gets puberty first: girls or boys

girls

When do boys catch up to girls?

around 35

What marks the start of adolescence in girls?

Menarche

Menarche

first menstruation (period)

• typically age 12

Percent body fat hypothesis of Menarche

suggests that women must have a certain % of body fat in order for menstruation to occur and be maintained.

• ex: girls who are active in sports may have a delayed menarche

Puberty onset: girls vs boys

girls = 8 or 9

boys = 10 or 11

Phenotypic signs of puberty in men

• Growth of testes and scrotal sac.
• pubic hair.
• Penis grows.
• facial and chest hair.
• Erections increase in frequency.
• Voice changes.

What marks the start of adolescence in boys?

Spermarche

Spermarche

First ejaculation

• can occur in wet dreams

What changes in behavior come with puberty?

Increased sensation-seeking behaviors.

• ex: Sex

Pursue social relations with peers and potential romantic partners.

• ex: Adolescents are motivated to seek social experiences with their peers and with potential romantic partners

The menstrual cycle is regulated by fluctuating levels of….

sex hormones

How does the menstrual cycle make humans unique among other pecies?

1. Menstrual cycle is unique to humans

2. Humans engage in sexual behavior outside ovulation

What is the length of Menstrual Cycle?

• 21-36 days

  • Average = 28 days

Length and timing of: Menstruation, Follicular phase, ovulation, and luteal phase in the cycle

Menstruation: Day 1 → Day 4/5

Follicular phase: Day 5 → Day 13

Ovulation: Day 14

Luteal phase: Day 15 → Day 28 (end of cycle)

Ovulation

When you are capable of reproduction, eggs are fertile

What is Mittelschmerz in the Menstrual Cycle?

when women feel themselves ovulating via cramping in the lower abdomen

What is an Anovulatory cycle?

When menstruation may take place without ovulation.

What physiological processes fluctuate with the menstrual cycle?

1. Cervical mucus cycle

2. Basal body temperature cycle

What does a drop in basal body temperature cycle mean?

it indicates ovulation has occured

What is Dysmenorrhea

debilitatingly painful menstruation

What is Dysmenorrhea caused by?

prostaglandins → chemicals that cause the uterine muscles to
contract.

What is Endometriosis?

A condition in which the endometrium grows abnormally outside
the uterus.

What is Amenorrhea

The absence of menstruation

What is Primary vs Secondary Amenorrhea?

Primary: No menstruation by about age 18.

Secondary: In girls who have had at least one period

What population is Secondary Amenorrhea common among?

Anorexic girls

• If they bleed

Girls who take birth control

Psychological features/disorders (beyond fluctuations in mood) associated with the Menstrual Cycle

1. PMS (Premenstrual Syndrome) → Severe physical and psychological symptoms (e.g., depression and irritability) that occur before menstruation.

• PMDD (premenstrual dysphoric disorder) → formalized as a diagnosis, severe pain and mood swings that occur

  • is rare

How does the menstrual cycle impact performance?

Evidence from cognitive tests does not show menstrual cycle fluctuations influence performance

• Psychological fluctuations in PMS are unclear.

  • only observed in Western Society

How does the menstrual cycle impact sex drive?

• evidence is unclear

  • some say it peaks during ovulation

  • some say it peaks before or after menstruation

• Caution is merited in using intercourse frequency as measure of sex drive

Psychological + social factors → sex drive

Why do we believe in PMS?

• We are thought to believe in PMS due to traditions and values that create negative attitudes/taboos toward menstruation.

  • In some cultures:

    • women are isolates

    • restrictive expectations of women

Cycles in Men

Some studies found fluctuations in testosterone levels

• Testosterone highest in morning