Lecture 6: Reproductive Behaviours Flashcards
What is Sex?
Biological/physiological characteristics
of males and females (e.g., reproductive
organs, chromosomes, hormones)
What is Gender?
Socially constructed
characteristics of women and men (e.g.,
norms, roles and relationships).
What Does The Gender Continuum Involve?
It involves scales for sexual orientation, gender identity, sex, and gender expression.
What is Natural Selection?
Individuals whose genes
help them survive will
produce more children,
and the next generation
will have more of these
genes.
What is Sexual Selection?
Genes that make an
individual more appealing
to the opposite sex will
increase the probability of
reproduction.
What is Intrasexual Selection?
Competition between
members of same sex
(usually males) for
access to mates
What is Intersexual Selection?
Members of one sex
(usually females)
choose members of
opposite sex
From the evolutionary standpoint of spreading one’s genes, men can succeed by either of two strategies..?
- Be loyal to one woman and devote your energies to helping her and her babies,
- Mate with many women and hope that some of them can raise your babies without your help
Which gender is more likely to seek multiple sex partners?
Men
What is the Sequence of Development of Sex Organs?
Sequence:
- Genetic Sex (XX, XY)
- Gonads (Testis/Ovaries)
- Sex Organs (Organizing Effects)
- Maturation (Organizing and Activating Effects)
How many genes are on the Y chromosome that are active in the specific brain areas?
At least 3 genes on the Y chromosome
are active in specific brain areas.
How many genes are on the X chromosome but only active in the female brain?
At least 1 gene on the X chromosome is active only in the female brain.
What determines
the genetic sex of the child?
1 Sex Chromosome
What is Meiosis?
It is a type of cell division that reduces the # of chromosomes in parent cell by half and produces four gamete cells.
What is Gamete?
A cell that fuses
with another cell during
fertilization.
What is Considered a Healthy Female?
- Fetal development: ~ 6 million eggs.
- At birth: 1 million eggs left.
- Puberty: 300,000 remain
What is a Healthy Male?
Produces million of sperm per day.
What are Organizing Effects?
- Sex hormones during prenatal development determines structure of
sex organs and brain - Long-term effects
- All in all it is the determination of internal and external sex
organs
Example: The first trimester of pregnancy for humans, sex hormones determine whether the body develops female or male genitals, and they alter certain aspects of brain development.
What are Activating Effects?
- Sex hormones activated
during postnatal stage
– E.g., Sperm production,
Erection, Ejaculation,
Ovulation, Sex drive - Short-term effects
– Cyclical (especially for
females) - Example: Current hormone levels influence the degree of sex drive.
When are sex organs are undifferentiated?
0-6 weeks
What Are The Development of Gonads?
Gonads (testes/ovaries) are the first to be determined
*Important for determining production of sperm/ova and sex hormones
*SRY gene on the Y chromosome causes gonads to become testes
*
What are the Undifferentiated precursor tissue for females called?
Mullerian ducts (female)
What are the Undifferentiated precursor tissue for males called?
Wolffian ducts (male)
Explain Becoming Female..
Müllerian system: The embryonic precursors of the female internal sex organs (fimbriae, fallopian tubes, uterus, inner 2/3 of vagina.
Explain Becoming Male..
Wolffian system: The embryonic precursors of the male internal sex organs (seminal vesicles, epididymis, vas deferens)
What are Androgens and Estrogens?
Together, they are are steroid hormones (also known as sex
hormones),
What is androgens?
The testes produce androgens (hormones that are more abundant in males) that increase the growth of the testes, causing them to produce more androgens
and so forth.
What is estrogen?
Hormones that are more abundant in females, the females’ ovaries produce more estrogens than androgens.
What is Progesterone?
This is another predominantly female hormone, prepares the uterus for the implantation of a fertilized ovum and promotes the maintenance of pregnancy.
What is Estradiol?
Most prominent type of estrogen, produced in ovaries.
What is Testosterone?
A steroid hormone that stimulates development of male secondary sexual characteristics, produced mainly in the testes
What is Dihydrotestosterone?
Male sex hormone found in the form of Testosterone.
How do steroid hormones work?
- Bind to membrane receptors to exert quick effects
- Activate proteins in the cell
- Alter expression of chromosomes to turn genes off/on.
What role does Testosterone play in organizing and activating effects?
Androgen
- Organizing: facial and body hair, lowers voice, muscular
development, genital growth - Activating: sex drive, reproduction
What role does Estradiol play in organizing and activating effects?
Estrogen
- Organizing: breast development, lining of uterus, body fat
deposition, maturation of female genitalia - Activating: sex drive, reproduction
What is Aneuploidy?
The condition of having an abnormal number of
chromosomes in a haploid set
Atypical Development: What is Turner’s Syndrome?
Characteristics of Turner’s Syndrome include..
Either entire X, or partial X chromosome is missing
*Result of defective sperm
*Gonads do not develop (non-working ovaries)
*Internal and external organs are female
*No estrogen, puberty must be induced
*Under-developed breasts, short stature, broad chested, webbed neck
*Other: learning disability, increased risk for CVD, immune disorders
How many people get Turner’s Syndrome?
1/2500 newborn females
Atypical Development: What is XXY, Klinefelter
Syndrome?
*Additional X from mother’s egg or father’s sperm
*Diagnosis in adulthood
*75% never diagnosed
Characteristics - Taller than average, greater abdominal fat, low muscle tone, less
facial/body hair, smaller sex organs, hypogonadal, infertile
How many people get XXY?
1/500 newborn males
Atypical Development: What is XX Male Syndrome?
*XX sex-reversal
*1/25,000 newborn males
*Genetic sex is “female” (XX)
*SRY is translocated to X chromosome
Characteristics - Male gonads (i.e., testes) are formed. Identify with and physically look male. Shorter than average, less hair, gynecomastia,
hypogonadal, smaller sex organs, infertile.
Atypical Development: What is Androgen
Insensitivity Syndrome (AIS)?
*Genetic sex is male (XY)
*Receptors do not respond to androgens
Range from:
■Complete AIS (external genitalia feminized)
■Partial AIS (partial genitalia masculinized)
■Mild (masculinized) AIS
*Present with internal testes, not ovaries or uterus
*Presentation from hypogonadal → Shallow vagina
*Infertile
Atypical Development: What is Persistent
Mullerian Duct Syndrome?
*Genetic sex is male (XY)
*Extremely rare (prevalence unknown; 250 reported cases in medical literature)
*Failure to produce AMH or no receptors for the hormone
*Present with female and male internal sex organs
*Undescended testes + Underdeveloped uterus
*Infertile
Atypical Development: What is Congenital Adrenal
Hyperplasia (CAH)?
Genetic sex is “female” (XX)
–1/15,000 newborn females
A genetic condition where the adrenal glands produce excess androgens (male hormones) in utero.
What did Ehrhardt (1975) study about CAH?
Ehrhardt studied girls with CAH to see whether prenatal androgen exposure influenced gendered behavior, especially those typically labeled as “masculine.”
Girls with CAH were more likely to:
- Prefer “boy-typical” toys (like trucks over dolls)
- Engage in rough-and-tumble play
- Show less interest in traditionally feminine activities
What happens to female rats exposed to testosterone during sensitive periods?
Female rats exposed to testosterone during sensitive periods become partly masculinized in anatomy and behaviour.
– Clitoris grows larger than normal.
– Sexual behaviour becomes masculinized.
What happens if a male rat lacks androgen receptors or is castrated?
It develops female-like anatomy and behaviour
What does the absence of sex hormones lead to?
The absence of sex hormones generally leads to
female-looking external genitalia
What happens to females who lack estradiol?
They do not have normal sexual behaviour.
Sex differences in the brain..
▪ Red: larger in women relative to the total mass of the brain.
▪ Blue: larger in men relative to the total mass.
What does the female hypothalamus generate?
Female hypothalamus generates a cyclic pattern of hormone release (menstrual cycle)
What does the male hypothalamus generate?
Male hypothalamus releases hormones steadily
What is the female-male difference in the Medial preoptic area, and what is it caused by?
In this area, there are more dendritic spines and
synapses in males. It is caused by Testosterone and estradiol increase production of prostaglandin E2
What is the female-male difference in the Ventromedial nucleus, and what is it caused by?
More widely branched dendrites in males, it is caused by estradiol activates PI3 kinase, which
increases glutamate release.
What is the female-male difference in the Arcuate nucleus and anteroventral periventricular nucleus, and what is it caused by?
More dendritic spines and
synapses in females. It is caused by estradiol increases GABA production, which acts on astrocytes to decrease dendritic branching.
What are the female-male sex differences in the brain during utero?
review this picture
What do Longitudinal studies on childhood play tell us?
Key Findings
*Exposure to high testosterone in utero associated with greater preference for boy toys among 3.5 yo girls.
*Exposure to phthalates in utero associated with
preference for girl toys among 3 and 6 y/o boys
What is an intelligence quotient (IQ)?
Total score derived from a
set of standardized tests or subtests designed to assess
human intelligence.
- No significant sex differences in general intelligence
Where do we see gender differences in particular types of intelligence?
- Spatial Abilities
- Verbal Abilities
What is the Male Advantage in spatial and verbal?
Men have the capacity to understand, reason and remember the spatial relations among objects or space
What is the Female Advantage in spatial and verbal?
The capability of a person to
express ideas using words in a clearly understandable manner
What is Levy’s Hypothesis?
Males have more lateralized (asymmetric) brain function, while Females have more bilateral (symmetric) brain organization.
You were just given $50000 to test the explanatory power of the biopsychosocial model to
better understand sex and/or gender differences. What is the first research question you test?
I think the first question should be does perceived (IV) influence the relationship between stress exposure and mental health outcomes (DV) differently for men and women?
What is the Mesolimbic system?
The mesolimbic pathway is part of the dopaminergic system (it uses dopamine as its main neurotransmitter) and connects several important brain regions involved in emotional and motivational processing…dopaminergic inputs from the ventral tegmental area (VTA) innervate brain regions
in the limbic system
What does Testosterone and estradiol activate?
Testosterone and estradiol leads to activation of DA in the hypothalamus and other brain regions mesolimbic pathway
What is the difference between DA 1 and 2?
DA circuitry is associated with reinforcement of sexual behavior and
anticipation of reward same in males and females
*D1 receptors: erection, receptive behaviour, commitment/fidelity
*D2 receptor: orgasm, attachment, mating bond
How is the menstrual cycle produced?
A woman’s hypothalamus and pituitary interact with the ovaries to produce the menstrual cycle, a periodic variation in hormones and fertility over the course of about 28 days.
After the end of a menstrual period, the anterior pituitary releases..
The follicle-stimulating hormone (FSH), which promotes the growth of a follicle in the ovary.
How does Testosterone affect sexual behaviour?
– Increases touch sensitivity in the penis and sexual arousal.
– Triggers the release of dopamine by the medial preoptic area (MPOA), and anterior hypothalamus
– Correlates with sexual interest
– Studies that inhibit GnRH – decrease sexual desire, fantasy and initiation of intercourse
What is an orgasm?
It is the release of oxytocin.
*From posterior pituitary
*Reproductive behavior: contraction of uterus; stimulates mammary gland
*Important for pair bonding/ attachment
*Decreases stress response and anxiety/fear
*Facilitates trust and other social behaviors
Bisexuality and sexual fluidity are more common…
In women
How do Genetics play a role in sexual orientation?
Genetics plays a role in sexual orientation, as shown by higher concordance rates in monozygotic (MZ) twins compared to dizygotic (DZ) twins.
Prenatal Influence in sexual orientation?
The fraternal birth order effect: having older brothers increases the probability of a subsequent son being gay
*Linked to a mother’s immune system reacting to a protein in male fetuses (NLGN4Y) in a way that alters the developing male
brain.
*Effect becomes more pronounced with each male gestation → each subsequent male pregnancy may increase concentration of anti-NLGN4Y antibodies (Bogart et al., 2018)
What do Imaging studies show about sexual orientation?
- Brain of gay men and straight women more symmetrical than brain of straight men and lesbians (Savic & Linstrom, 2008).
- Straight women and gay men display more amygdala
connections on left side compared to increased right activation found in straight men. - Third interstitial nucleus of the anterior hypothalamus (INAH- 3): straight men > gay men = straight women (LeVay, 1991)
