Reproductive behaviours Flashcards
Mullerian ducts and Wolffian ducts
In early prenatal development, males and females start with the same anatomy.
- Both have Müllerian ducts (precursors to female internal structures) and Wolffian ducts (precursors to male internal structures).
SRY (sex-determining region on the Y chromosome) gene:
A gene on the Y chromosome responsible for causing the primitive gonads in males to become testes.
Testes:
Sperm-producing organs which produce androgens (male hormone).
Wolffian ducts:
Precursors of the male reproductive organs that develop into seminal vesicles (sac-like structures that store semen) and the vas deferens (a duct from the testes into the penis) after testosterone exposure during prenatal development.
- Testosterone also results in the development of the penis and scrotum.
In genetic females (XX)
more estrogen than androgens are produced and primitive gonads become ovaries (egg-producing organs), her Wolffian ducts degenerate, and her Müllerian ducts develop and mature as long as she is not exposed to large amounts of testosterone.
Steroid hormones,
like estrogen, contain four carbon rings and are derived from cholesterol. Steroid hormones exert their effects in three ways:
a. They can bind to membrane receptors like protein or peptide hormones.
b. They can enter cells and activate certain kinds of proteins in the cytoplasm.
c. They can bind to chromosomes where they activate or inactivate specific genes.
Androgens and Estrogens:
categories of chemicals. Neither is a specific chemical itself. Androgens promote the development of typically masculine features (like facial hair) and estrogens promote typically female features (like breast development).
Testosterone:
the most widely known androgen.
Estradiol:
the most prominent type of estrogen. Levels are higher in women than men.
Progesterone:
Another predominantly female hormone. Progesterone prepares the uterus implantation of a fertilized ovum and promotes the maintenance of pregnancy.
Organizing effects of sex hormones
occur mostly during a sensitive stage of development and determine whether the brain and body develop as male or female.
Activating effects of sex hormones
are more temporary and happen only while the hormone is present. Activating effects can occur at any time in life.
Sensitive period:
Time early in prenatal development during which a particular event has a long-lasting effect. For example, testosterone controls the development of external genitalia in humans during the third and fourth months of pregnancy.
The sexually dimorphic nucleus:
Part of the medial preoptic hypothalamus that is larger in the male than in the female. This area is linked to male sexual behavior.
b. The female hypothalamus differs from the male hypothalamus in that the former can generate a cyclic pattern of hormone release, whereas the latter cannot.
Alpha-fetoprotein:
A protein that binds with estrogen and keeps it from entering cells during the early sensitive period (this process prevents females from becoming masculinized by their own estrogen).
Impotence:
Inability to have an erection (this is usually not caused by low testosterone levels in the body). Impotence can be treated by increasing blood circulation in the penis and hypothalamus.
follicle-stimulating hormone (FSH):
At the end of the menstrual period, the anterior pituitary releases follicle-stimulating hormone (FSH) that promotes the growth of a follicle in the ovary.
Toward the middle of the menstrual cycle,
the follicle produces increasing amounts of estradiol (a type of estrogen); this leads to an increased release of FSH and luteinizing hormone (LH) from the anterior pituitary. FSH and LH cause the follicle to release an ovum. Progesterone is released from the remnant of the follicle and prepares the uterus for implantation of a fertilized ovum.
Periovulatory period:
Midway point of the menstrual cycle when sexual interest increases, possibly due to high estrogen levels.
Oxytocin
i. Oxytocin is important for reproductive behavior because it stimulates contractions of the uterus during delivery of a baby and stimulates the mammary gland to release milk.
ii. Sexual pleasure also releases oxytocin, especially at orgasm, which is typically experienced as a state of relaxation and decreased anxiety.
iii. Oxytocin is also responsible for the formation of pair bond, like the bond between two mating partners or the bond between mother and infant.
Gender identity:
How we identify sexually and what we call ourselves (male or female). Sex differences are the biological differences between males and females. Gender differences are the differences that result from people’s thinking about themselves as male or female.
Hermaphrodites:
Individuals whose genitals do not match the normal development for their genetic sex. A true hermaphrodite has some normal testicular tissue plus ovarian tissue.
Congenital adrenal hyperplasia (CAH):
Condition where there is overdevelopment of the adrenal gland from birth. This overdevelopment leads to an excess release of testosterone. In genetic males, the extra testosterone has little effect but in genetic females it causes masculinization of the external anatomy. For example, the structural appearance of the clitoris may resemble a penis.
Intersexes:
Individuals whose development is intermediate between male and female.
Androgen insensitivity or testicular feminization:
Genetic males with the genital appearance of a female. This abnormality is caused by the inability of androgens to bind to genes in a cell’s nucleus; consequently, cells are insensitive to androgens and the external genitals develop similar to those of a female.
b. Ranges from a smaller-than-average penis to genitals that look like a normal female’s. In some cases, they are considered a normal female until puberty, when they do not menstruate.
