Chapter 4: Hormones and Chromosomes Flashcards
Endocrine Glands
Secrete hormones and are important to development of the sexes
-releasing hormones are produced by the hypothalamus to stimulate the pituitary gland which produces tropic hormones to stimulate the gonads
(endocrine glands release hormones, hypothalamus stimulates the pituitary gland which produces tropic hormones)
Gonads secrete steroidal hormones which are related to reproductive functioning
- Androgens, most common is testosterone
-Estrogens, most common is estradiol - Progestins, most common is progesterone
both males and females produce all three but in different proportions
What are the stages of Sexual Dimorphism
- beginning at conception
- Genetic stage: inheritance of sex chromosomes
X and Y - Gonadal Stage: the development of reproductive organs
-Hormonal Stage: androgens and estrogens, prenatally and pubertal
Internal Reproductive System
about six weeks after conception
-the difference in timing (internal vs external) allows for the possibility of errors in developing either the male or female patterns
When Does External Genitalia Develop
about 3 months into prenatal development
- the difference in timing allows for the possibility of errors in developing either the male or female patterns
Internal Structures Related to reproduction
- women: ovaries, fallopian tubes, uterus, upper vagina
- Men: testes, prostate glands, seminal vesicles, vas deferens
External Structures Related to Reproduction
Women: clitoris , labia, vaginal opening
Men: penis, scrotum
Sexual Differentiation
Chromosomes
- 23 pairs normally
- ovum 23 and sperm cell 23
- pair 23 is critical because it is our sex chromosomes
Development of Male and Female Physiology
within the first 6 weeks of development there are no differences between male and female embryos
- both sexes start with the same internal reproductive system, initially identical, both capable of developing into male or female
- gene on the y chromosome prompts development of the testes which produce androgens during prenatal development
Wolffian System
- the capacity to develop according to the male pattern if exposed to androgrens
Mullerian System
- the capacity to develop according to the female pattern if not exposed to androgens
The Male Process of Developing Reproductive Organs
- Must have the presence of androgens
- androgens prompt the development of the wolffian system
- secretion of mullerian-inhibiting substance causes the mullerian system to degenerate
- gonads develop into testes
The Female Process of Developing Reproductive Organs
- The absence of androgens allows the mullerian system to develop
- the wolffian system degenerates
- the gonads develop into ovaries
Development of External Genitalia
- this process begins in the third month of prenatal development
- ANDROGENS ARE CRITICAL, the presence of androgens creates the male pattern
- no androgens= female pattern
Brain size and gender differences
- proportion is similar to differences In body size
Cerebral Hemisphere Differences in the sexes
-lateralization of function occurs
(left- language, speech)
(right- spatial abilities)
men have more lateralization than women for language and spatial abilities but not significant.
Sexually Dimorphic Nucleus (SDN)
- potential sex difference in brain structure
- located in the hypothalamus
- the most prominent brain difference
- 2.5 times larger in men than in women
- functions in humans is not yet understood but may be relate to sexual behaviour and gender identity
Primary Sexual Characteristics
- maturity of sexual organs
- reproductive maturity
Secondary Sexual Characteristics
- physical features that reflect sexual maturation but are involved directly in reproduction
Luteinizing Hormone (LH) and Follicle-Stimulating Hormone (FSH)
- released by the pituitary gland and stimulates the gonads to increase production of estrogens and androgens
- this results in the maturation of genitals and produces the menstrual cycle
LH and FSH differ in what way
LH- causes follicle to rupture and release ovum, involved in the maturation of sperm
FSH- stimulates follicles to mature an ovum, involved in sperm production
Errors in meiosis can alter the sex chromosomes
XO = Turner Syndrome XXY= klinefelter syndrome
Tuner Syndrome XO
- from error during meiosis
- missing chromosome
- appear female at birth (but their mullerian system has degenerated) meaning no functional ovaries
- no estrogen or puberty
- hormone supplements
Klinefelter Syndrome XXY
- error during meiosis
- male internal and external genitalia
- small testes, usually sterile
- may develop breasts and a feminized body during puberty
- developmental disorders
Sexual development problems related to prenatal hormone exposure
- congenital adrenal hyperplasia
- Androgen Insensitivity Syndrome
Congenital Adrenal Hyperplasia (Adrenogenital Syndrome)
- related to prenatal hormone exposure
- caused by an increase in androgen production
- for XY males, typically few problems occur (during early puberty)
- for XX females, causes masculinization of external genitalia
- can be fixed with surgery (controversial)
- “Tomboy” but majority identify as female
Androgen Insensitivity Syndrome
- related to prenatal hormone exposure
- affects chromosomal XY males
- androgen receptors do not work so there is no production of mullerian- inhibiting substance.
- external genitalia appear female but have undescended testes , no internal female genitalia
- not typically identified until puberty when they fail to reach menarche and do not grow pubic hair
- identify as female
Intersexuality (Hermaphroditism)
- Disorder of Sexual Development
- restricted to individuals who have both ovarian and testicular tissue
- RARE only 60 cases In north america and europe in the last century
5-Alpha-Reductase Deficiency
- Extremely rare
- affects XY males
- appear female at birth but ambiguous
- develop according to the male pattern during puberty, respond to androgens
- 60% developed male gender and 40% retained female gender
Premenstrual Syndrome (PMS)
- negative emotional, cognitive and physical symptoms
- result of hormonal changes prior to menstruation
- difference between menstrual symptoms and emotional and cognitive symptoms
- no relationship between hormone levels and pms
Pre-Menstrual Dysmorphic Disorder
-treated with antidepressants
The relationship between testosterone and aggression in humans
- complex
- testosterone increases aggression (little support)
- aggression increases testosterone
- aggression and testosterone are mediated. either biological or social
- high testosterone linked to impulsivity (e.g. drugs and alcohol) and antisocial (lack of consideration for others)
- complex interaction of high testosterone, low cortisol and low serotonin
Berdaches
Two-spirit
- not intersex and not homosexual
- native american
Hijras
Third Sex in india
may be intersex
