brain and behavior ch 10 reproductive behavior

sex

genetic or physiological characteristics of males and females

gender

socially-influenced identity, role, and/or behavior of an individual

intersex

broad term used to describe a variety of combinations of biologically male and female characteristics, such as an individual born with external female genitalia and internal male sex organs

all cells of the human body

(other than sperms or ova) contain 23 pairs of chromosomes

-the genetic info that programs the development of a human is contained in the DNA that constitutes these chromosomes

gametes

a mature reproductive cell: (ova and sperms)

-entails a special form of cell division called meiosis

-Meiosis: produces cells that contain one set of each of the pairs of chromosomes. The development of a human begins at the time of fertilization, when a single sperm and ovum join, sharing their 23 single chromosomes to reconstitute the 23 pairs

genetic sex

-determined by presence of XX (female) or XY (male) chromosomes

-determined at the time of fertilization of the ovum by the father's sperm

-twenty-two of the 23 pairs of chromosomes determine the organism's physical development independent of its sex

sex chromosomes

--the last pair of the 23 chromosomes that determines whether the offspring will be genetically male or female

-the last pair consists of two chromosomes

-the X and Y chromosomes, which determine an organism's genetic sex. typically, XX individuals are female, and XY individuals are male

gonads

1 of the 3 general categories of sex organs

-testes or ovaries

-are the first to develop

-they have two(dual) functions: they produce ova or sperms, and they secrete hormones

SRY

-(sex-determining region Y)

-the gene on the Y chromosome whose product instructs the undifferentiated fetal gonads to develop into testes

sixth week of prenatal development

male and female fetuses are identical

-both sexes have a pair of identical undifferentiated gonads, which have the potential of developing into either testes or ovaries

-the SRY gene is the factor that controls their development into testes and determines the male sex

-this gene produces a protein that binds to the DNA of cells in the undifferentiated gonads and causes them to become testes

-if the SRY gene is not present, the undifferentiated gonads become ovaries

XX males example

this can occur when the SRY gene becomes translocated from the Y chromosome to the X chromosome during production of the father's sperms.

-although the SRY gene begins the process of gonadal differentiation, at least two other genes are also necessary for completion of this process

organizational effect (of hormone)

the effect of a hormone on tissue differentiation and development

-second step after the gonads have developed

-determines the individual's sexual development

-during prenatal development these hormones have organizational effects, which influence the development of a person's sex organs and brain

-these effects are permanent and persist throughout the person's life

activational effect

the effect of a hormone that occurs in the fully developed organism; may depend on the organism's prior exposure to the organizational effects of hormones

-the second role of sex hormones

-these effects occur later in life, after the sex organs have developed

-ex: hormones activate the production of sperms, make erection and ejaculation possible, and also induce ovulation

internal sex organs

early in embryonic development the internal sex organs are bisexual; all embryos contain the precursors for both female and male sex organs

-during the third month of gestation, only one of these precursors develops

Mullerian system

the embryonic precursors of the female internal sex organs

-develops the fimbriae and Fallopian tubes, the uterus, and the inner two-thirds of the vagina

-it doesn't need any additional hormonal stimulus from the gonads to develop

Wolffian system

the embryonic precursors of the male internal sex organs

-develops the epididymis, vas deferent, and seminal vesicles

-the cells of the Wolffian system do not develop unless they are stimulated to do so by a hormone

-testes secrete two types of hormones

anti-mullerian hormone

a peptide secreted by the fetal testes that inhibits the development of the Mullerian system, which would otherwise become the female internal sex organs

-prevents the Mullerian (female) system from developing (it has a defeminizing effect)

defeminizing effect

an effect of a hormone present early in development that reduces or prevents the later development of anatomical or behavioral characteristics typical of females

androgens

-a set of steroid hormones

-a male sex steroid hormone. testosterone is the principal mammalian androgen

-srimulates the development of the Wollifan system.

-androgens have a masculinizing effect

masculinizing effect

an effect of a hormone present early in development that promotes the later development of anatomical or behavioral characteristics typical of males

testosterone

the principal androgen found in males

-one of 2 androgens that are responsible for masculinization

-is secreted by the testes and gets its name from these glands

dihydrotestosterone

an androgen, produced from testosterone through the action of the enzyme 5beta reductase

androgen insensitivity syndrome

a condition caused by a congenital lack of functioning androgen receptors; in a person with XY chromosomes, causes the development of a female with testes but no internal sex organs

-a genetic mutation that prevents the formation of functioning androgen receptors

-the gene for the androgen receptor is located on the X chromosome

-the primitive gonads of a genetic male fetus with androgen insensitivity syndrome becomes testes and secrete both anti-Mullerian hormone and androgens

-the lack of androgen receptors prevents the androgens from having a masculinizing effect thus the epididymis, vas deferens, seminal vesicles, and prostate do not develop

-however the anti-Mullerian hormone still has its defeminizing effect, preventing the female internal sex organs from developing thus the uterus, fimbriae, and Fallopian tubes don't develop either, and the vagina is shallow

-the external genitalia are female, and at puberty the person develops a woman's body. Without a uterus and ovaries, the person can't have children

persistent Mullerian duct syndrome

-second genetic disorder

-a condition caused by a congenital lack of anti-Mullerian hormone or receptors for this hormone; in a male, causes development of both male and female internal sex organs

-has two causes: either a failure to produce anti-Mullerian hormone or the absence of receptors for this hormone

-when this syndrome occurs in genetic males, androgens have their masculizing effect, but defeminizing doesn't occur.

-the person is born with both sets of internal sex organs, male and female. the presence of the additional female sex organs usually interferes with functioning of the male sex organs

Turner syndrome

-the presence of only one sex chromosome (an X chromosome); characterized by lack of ovaries but otherwise normal female sex organs and genitalia

-they have X0 cells -(zero) missing chromosome. X come from the mother

-ovaries aren't produced since two X chromosomes are needed

-even though they have no gonads at all, their biological development is female, with typical female internal sex organs and external genitalia

-proves that fetuses don't require ovaries or the hormones they produce to develop as females

-people with this syndrome take supplemental estrogen to induce puberty and sexual maturation, but without ovaries they can't produce ova

external genitalia

-the external genitalia don't need to be stimulated by female sex hormones to become female

-in the presence of dihydrotestosterone, the external genitalia will become male

-the development of a person's external genitalia is determined by the presence or absence of an androgen

-explains why people with Turner syndrome have female external genitalia even though they lack ovaries

-people with androgen insensitivity syndrome have female external genitalia too, because without androgen receptors, their cells can't respond to the androgens produced by their testes

primary sex characteristics

are influenced by organizational effects of hormones and include the gonads, internal sex organs, and external genitalia

-these structures are present at birth

secondary sex characteristics

-enlarged breasts and widened hips or a beard and deep voice are influenced by the activational effects of hormones and do not appear until puberty

-at puberty the gonads are stimulated to produce their hormones, and these hormones cause the person to mature sexually. the onset of puberty occurs when cells in the hypothalamus secrete GnRH

GnRH (gonadotropin-releasing hormone)

-a hypothalamic hormone that stimulates the anterior pituitary gland to secrete gonadotropic hormone

stimulate the production and release of two gonadotropin hormones by anterior pituitary gland

gonadotropic hormones (FSH and LH)

a hormone of the anterior pituitary gland that has a stimulating effect on cells of the gonads

stimulate the gonads to produce their hormones, which are ultimately responsible for sexual maturation

-both FSH and LH are named for the effects they produce in a female

-however the same hormones are produced in males, where they stimulate the testes to produce sperms and to secrete testosterone

-both types of glands also produce a small amount of the primary hormones of the other sex

-both estradiol and androgens initiate closure of the growing portions of the bones and thus halts skeletal growth

Follicle stimulating hormone (FSH)

-one of the two gonadotropic hormones

The hormone of the anterior pituitary gland that causes development of an ovarian follicle and the maturation of an ovum.

luteinizing hormone (LH)

-one of the two gonadotropic hormones

a hormone of the anterior pituitary gland that causes ovulation and development of the ovarian follicle into a corpus luteum

kisspeptin

a peptide produced by neurons in the arcuate nucleus of the hypothalamus under the control of leptin receptors; essential for initiation of puberty and maintenance of reproductive ability

-controls the secretion of GnRH

-produced by neurons in the arcuate nucleus of the hypothalamus, is essential for the initiation of puberty and the maintenance of male and female reproductive ability

leptin

a peptide hormone secreted by well nourished fat cells, provides an important signal to the Brain concerning the amount of fat tissue in the body

-if body fat increases, the level of leptin in the blood increases and signals the brain to suppress appetite

-the hormone also plays a role in determining the onset of puberty in females: it acts on leptin receptors found on kisspeptin-secreting neurons in the arcuate nucleus

estradiol

the principal estrogen of many mammals, including humans

-is produced by the ovaries

-steroid sex hormone

estrogen

a class of sex hormones that cause maturation of the female genitalia, growth of breast tissue, and development of other physical features characteristic of females

menstrual cycle

the female reproductive cycle of most primates, including humans; characterized by growth of the lining of the uterus, ovulation, development of a corpus lute, and (if pregnancy does not occur), menstruation

estrous cycle

the female reproductive cycle of mammals other than primates

-is typically shorter than the menstrual cycle

ovarian follicle

a cluster of epithelial cells surrounding an oocyte, which develops into an ovum

the cycles

-sequence of events

-are controlled by hormonal secretions of the pituitary gland and ovaries

-these glands interact, the secretions of one affecting those of the other

-a cycle begins with the secretion of gonadotropins by the anterior pituitary gland

-these hormones stimulate the growth of ovarian follicles

-women normally produce one ovarian follicle each month; if two are produced and fertilized, dizygotic (fraternal) twins will develop

-monozygotic (identical) twins develop from the same ovum and follicle

-as ovarian follicles mature, they secrete estradiol, which causes growth of the lining of the uterus in preparation for implantation of the ovum, should it be fertilized by a sperm

-feedback from the increasing level of estradiol eventually triggers the release of a surge of LH by the anterior pituitary gland

-the LH surge causes ovulation

-the ovarian follicle ruptures, releasing the ovum

-under the continued influence of LH, the ruptured ovarian follicle becomes a corpus luteum

-corpus lute produces estradiol and progesterone

-the ovum enters one of the Fallopian tubes and begins its progress toward the uterus

-if it meets sperm cells during its travel down the Fallopian tube and becomes fertilized, it begins to divide, and several days later it will implant itself into the uterine wall

-if the ovum is not fertilized or if it is fertilized too late to develop sufficiently by the time it gets to the uterus, the corpus luteum will stop producing estradiol and progesterone, and then the lining of the walls of the uterus will slough off. at this point, menstruation will commence

corpus luteum

a cluster of cells that develops from the ovarian follicle after ovulation; secretes estradiol and progesterone

progesterone

a steroid hormone produced by the ovary that maintains the endometrial lining of the uterus during the later part of the menstrual cycle and during pregnancy; along with estradiol it promotes receptivity in female mammals with estrous cycles

-promotes pregnancy(gestation)

-maintains the lining of the uterus, and it inhibits the ovaries from producing another follicle

refractory period

a period of time after a particular action during which that action can't occur again

Coolidge effect

the restorative effect of introducing a new female sex partner to a male that is in a refractory period

oxytocin

a hormone secreted by the posterior pituitary gland; causes contraction of the smooth muscle of the milk ducts, the uterus, and the male ejaculatory system; also serves as a neurotransmitter in the brain

-released at the time of orgasm in both males and females and appears to contribute to the contractions of the smooth muscle in the male ejaculatory system and of the vagina and uterus

-plays an important role in establishment of pair bonding

estrus

a period of sexual receptivity in many female mammals (excluding humans)

-during a receptive period in the estrous cycle

lordosis

a spinal sexual reflex seen in many four-legged female mammals; arching of the back in response to the approach of a male or to touching the flanks, which elevates the hindquarters

receptivity

a female's ability and willingness to copulate by displaying lordosis when a male attempts to mount her.

perceptivity

a female's interest in copulation, as shown by seeking out a male and engaging in behaviors that tend to increase his sexual interest

attractiveness

physiological and behavioral changes in the female that affect the male

-most responsive to females who are in the estrus phase of the estrous cycle

behavioral defeminization

the organizational effect of androgens that prevents the animal from displaying female sexual behavior in adulthood

-accomplished by suppressing the development of neural circuits controlling female sexual behavior

behavioral masculinization

the organizational effect of androgens that enables animals to engage in male sexual behavior in adulthood

-accomplished by stimulating the development of neural circuits controlling male sexual behavior

pheromone

A chemical released by one animal that affects the behavior or physiology of another animal; usually smelled or tasted

vomeronasal organ (VNO)

a sensory organ that detects the presence of certain chemicals, especially when a liquid is actively sniffed; mediates the effects of some pheromones

-consists pf a small group of sensory receptors arranged around a pouch connected by a duct to nasal passage

-contains over 200 G-protein-linked receptor molecules that detect many of the chemicals that serve as phreomenes

accessory olfactory bulb

A neural structure located in the main olfactory bulb that receives information from the vomeronasal organ

-sends axons to the medial nucleus of the amygdala, which in turn projects to the pre optic area and anterior hypothalamus and to the ventromedial nucleus of the hypothalamus

medial nucleus of the amygdala

A nucleus that receives olfactory information from the olfactory bulb and accessory olfactory bulb; involved in the effects of odors and pheromones on reproductive behavior.

Lee-boot effect

the slowing and eventual cessation of estrous cycles in groups of female animals that are housed together; caused by a pheromone in the animals' urine; first observed in mice

whitten cycle

the synchronization of the menstrual or estrous cycles of a group of females, which occurs only in the presence of a pheromone in a male's urine

Vandenbergh effect

the earlier onset of puberty seen in female animals that are housed with males; caused by a pheromone in the male's urine; first observed in mice

bruce effect

termination of pregnancy caused by the odor of a pheromone in the urine of a male other than the one that impregnated the female; first identified in mice

Androstadienone (AND)

found in men's sweat, increases alterness and positive mood in women but decreases positive mood in men

EST (estratetraene)

activated the paraventricular nucleus and dosomedial hypothalamus in men but not in women

medial pre optic area (MPA)

an area of cell bodies just rostral to the hypothalamus ; plays an essential role in male sexual behavior

Sexually Dimorphic Nucleus (SDN)

A nucleus in the preoptic area that is much larger in males than in females; first observed in rats; plays a role in male sexual behavior

- the size of this nucleus is controlled by the amount of androgens present during fetal development

-the critical period for masculinization of the SDN appears to start on the eighteen day of gestation and end once the animals are five days old

periaqueductal gray matter (PAG)

the region of the midbrain that surrounds the cerebral aqueduct; plays an essential role in various species-typical behaviors, including female sexual behavior

nPGI (nucleus paragigantocellularis)

a nucleus of the medulla that receives input from the medial preoptic area; contains neurons whose axons form synapses with motor neurons in the spinal cord that participate in sexual reflexes in males

ventromedial nucleus of the hypothalamus (VMH)

a large nucleus of the hypothalamus located near the walls of the third ventricle; plays an essential role in female sexual behavior

Congenital Adrenal Hyperplasia (CAH)

a condition characterized by hypersecretion of androgens by the adrenal cortex; in females, causes masculinization of the external genitalia

-the secretion of androgens begins prenatally; thus, the syndrome causes prenatal masculinization

-a girl born with CAH will be born with an enlarged clitoris, and her labia may be partly fused together

-once the syndrome has been identified, the person will be given a synthetic hormone that suppresses the excessive secretion of androgens

cloacal exstrophy

results in the birth of an intersex individual who is genetically male with fully developed testes but urogenital abnormalities, often including the lack of a penis. in the past, many genetically male individuals born with this condition were raised as females, primarily because it is relatively easy to surgically construct a vagina that can function in intercourse but very difficult to construct a functioning penis. approx. 50 % of intersex individuals with cloacal exstrophy later expressed dissatisfaction with their surgical gender assignment and began living as men, often undergoing gender-change procedures. these individuals are often sexually attracted to females. (social pressure against someone who has been raised as a girl subsequently adopting a Male sex role)

parturition

act of giving birth

prolactin

a hormone of the anterior pituitary gland, necessary for production of milk; also facilitates maternal behavior