Behavioral Neuroscience: Hormones and Sexual Behavior

Androgen Insensitivity Syndrome

46, XY. Genetic males, but phenotypic females with female gender identities (but not internal reproductive organs, infertile). Abnormal androgen receptors disrupt normal development of the Wolffian system, though testosterone and anti-Mullerian hormone (preventing the development of the female Mullerian system) are released in a normal manner.

Differentiation of Male Gonads

6 weeks after conception, gonads are undifferentiated. Sex-determining region of the Y chromosome (SRY gene) → testis-determining factor protein → primordial gonads develop into testes. Without the SRY gene, gonads become ovaries.

Testosterone

A type of androgen that is secreted by the testes via SRY gene during the 3rd month. Has a masculinizing effect and promotes the development of the Wolffian system.

Congenital Adrenal Hyperplasia (CAH)

Adrenal glands release elevated levels of androgens. Males: few observable effects. Females: exposed to excessive androgen; born with ambiguous external genitalia.

cholesterol

All sex hormones come from __________________.

Transexuality

An individual's gender identity is inconsistent with his/her biological sex.

Finger Digit Ratios

Androgen and estrogen receptors are present on both digits 2 and 4, but more on digit 4. With higher testosterone and lower estrogen, the hand develops in the masculine pattern (shorter 2nd digit, longer 4th digit). With higher estrogen and lower testosterone, the hand develops in the female pattern (equal 2nd and 4th digits).

5-Alpha-Reductase Deficiency

At puberty, unconverted testosterone produces male secondary sex characteristics.

Sex

Biological characteristic of being male or female.

Sex Hormone Synthesis

Cholesterol → progesterone → testosterone. Aromatization necessary to form estradiol. Estradiol → estrogens. Males and females produce both androgens and estrogens, but in different amounts.

Symmetry

Degree of similarity of one side of the face or body to the other. Important factor in attraction.

Wolffian System

Develops into the seminal vesicles, vas deferens, and prostate.

Mullerian System

Develops into the uterus, upper vagina, and fallopian tubes.

Brain on Love

Dopamine: Up. More pleasure and motivation, less sadness. Oxytocin: Up. More trust and attachment, less fear. Vasopressin: Up. More arousal and attraction, less anxiety. Serotonin: Down. More obsession and aggression.

Activational Effects

Effect of a hormone that occurs in the fully developed organism, beginning at the time of puberty. Short-term and reversible.

Female Secondary Sex Characteristics

Estradiol stimulates: -Breast growth -Maturation of external genitalia and uterus -Changes in deposition of body fat -Menstrual cycle

XX

Female

External Genitalia

Females: labia, clitoris, and outer vagina. No hormonal activity required for the development of female genitalia. Males: scrotum and testes. 5-alpha-dihydrotestosterone needed for development of male genitalia; loss results in ambiguous external genitalia. Converted from testosterone by the enzyme 5-alpha-reductase.

Menarche

First menstrual cycle. Mean age of onset has decreased over the years. Possible causes: increasing rates of obesity or increased exposure to estrogen-like compounds.

Organizational Effects

Hormonal effects on the differentiation and development of the sex organs, brain, and behavior in early development. Long-term and irreversible. Associated with critical or sensitive period.

Anti-Mullerian Hormone

Hormone secreted by the testes via SRY gene during the 3rd month. Has a defeminizing effect and prevents the Mullerian system from developing.

46

How many chromosomes do humans have?

male; female

In males, testosterone promotes _________-typical behavior, while estradiol suppresses _______________-typical behavior.

female

In the presence of estradiol and progesterone, and in the absence of androgens, the brain develops in the _____________ pattern.

Gonads

Internal sex organs. Females: ovaries. Males: testes. Functions: to produce eggs or sperm and to secrete hormones.

Gender

Learned/sociocultural characteristic of being masculine or feminine.

XY

Male

Sex Differences

Mediated by: -Continued expression of genes on both X and Y chromosomes, especially in the brain. -Hormone effects -Epigenetics -Societal and cultural influences

Vasopressin

Neurohormone important for social behavior, sexual motivation, and pair-bonding. Expressed more by males.

Oxytocin

Neurohormone secreted during childbirth and lactation. Promotes pair-bonding. Expressed more by females. Released during orgasm by both sexes.

Postpartum Depression

New mothers experience feelings of depression due to rapidly changing hormonal environment.

Female Hormonal Contraception

Oral contraceptives: Interfere with normal ovulation. Prevents maturation of follicles and ovulation. Contain estrogen and progestin. Injections: Progestin, administered every 3 months. Implants: Release progestin over a period of 6 months. Over types: IUD, ring, patch, emergency contraception

Female Activational Effects of Sex Hormones

Ovarian hormones do not control women' sex drive, but may influence sexual interest. Testosterone activates sexual behavior. Estrogen enhances sex drive during peak fertile days (ovulation), while progesterone dulls sex drive.

Gender Identity

Person's self-concept as male or female.

Premenstrual Syndrome (PMS)

Physical and psychological symptoms immediately prior to the onset of menstruation.

Attraction

Preference for younger features on females. Preferences for masculine men (testosterone-related facial features) for casual sexual encounters. Less masculine men are preferred for long-term partners. Smell preference for an immune system different from our own; want to mate with someone with a different immune system because offspring will be healthier.

Premenstrual Dysphoric Disorder (PMDD)

Premenstrual mood changes are unusually severe, affecting daily life.

Testosterone

Regulates sex drive in both men and women. Lower in older men, those in long-term relationships, and following the birth of a baby. Increases in anticipation of competition and further increases in winners.

Turner Syndrome

Sex chromosome abnormality. 45, X0. Phenotypic female. Abnormal growth patterns, short in stature, lack prominent female secondary sex characteristics, sterile, and may have slight mental retardation.

Klinefelter Syndrome

Sex chromosome abnormality. 47, XXY. Phenotypic male. Hypogonadism (small testes), infertile. Tall stature with some female secondary sex characteristics such as wide hips and breast growth. Often requires testosterone treatment at puberty for masculine traits.

Supermale

Sex chromosome abnormality. 47, XYY. Genetic and phenotypic male. Normal sexual development, may have very slightly reduced fertility. May have increased risk of acne and learning disabilities. Minor risk factor for impulsive, antisocial, and criminal misbehavior.

Puberty

Sexual maturation and the development of secondary sex characteristics. The hypothalamus releases gonadotropin-releasing hormone to the pituitary gland → the pituitary gland releases gonadotropins (leutinizing hormone and follicle stimulating hormone) → secretion of sex hormones from the gonads

Otoacoustic Emissions

Sounds emitted by the cochlea that show sex differences. Females produce a higher number of spontaneous otoacoustic emissions than males. Females produce louder click-evoked otoacoustic emissions than males. Otoacoustic emissions presumably indicate the influence of prenatal testosterone levels.

Sexual Orientation

Stable pattern of attraction to members of a particular sex. Not synonymous with sexual behavior. Not purely dichotomous. Males: 96-98% heterosexual, 2-4% homosexual Females: 98-99% heterosexual, 1-2% homosexual

Male Secondary Sex Characteristics

Testosterone stimulates: -Muscular development -Maturation of external genitalia -Facial and body hair -Enlargement of larynx -Hairline on the head

Coolidge Effect

The propensity of an animal that appears sexually satiated to resume sexual activity when provided with a novel partner.

Ovulation

The time when females' sexual interest is at its highest.

True

True or false: All embryos have precursors to male and female internal organs.

True

True or false: Homosexual individuals perform similarly to their opposite sex. INAH-3 (hypothalamic nucleus) is smaller among women and homosexual men than among heterosexual men. Thus, homosexual men show a more female-typical pattern.

True

True or false: In terms of gonads, female is the default. To become male, must have the SRY gene to undergo gonad differentiation.

True

True or false: Males and females produce both androgens and estrogens, but in different amounts.

True

True or false: Males habituate more to sexually arousing stimuli than females.

True

True or false: Ovaries are not active during fetal development; the Mullerian system develops in the absence of male hormones.

True

True or false: Preferences for masculinity vary based on the fertility cycle and whether a woman is taking hormonal contraception. Preference for more masculine looking faces when conception risk is high. More accurate when judging male sexual orientation as a function of fertility status during ovulation.

True

True or false: There are ethical constraints to prenatal manipulation in humans.

True

True or false: We are all more similar than we are different. Sex differences are very subtle.

Androgen

Type of steroid hormone that develops and maintains typically masculine characteristics or sexual interest. Present in both males and females. Most well-known is testosterone. Precursor for estrogen.

Fertilization

When genetic sex is determined. Depends on whether the sperm carries an X or Y sex chromosome.

Men

Which gender is better at spatial tasks? Related to higher levels of androgens.

Women

Which gender is better at verbal tasks (speak first, read with a greater proficiency, better vocab)? Related to higher levels of estrogen.

23

Which pair of chromosomes are the sex chromosomes?

Aromatization; androgens

__________________ masculinizes brains of many animals while __________________ play a greater role in the masculinization of humans.