Chapter 11 – Reproductive Behaviors

Question 1

Male and female mammals start with the same anatomy during an early stage of prenatal development. Both have a set of (2) as well as:

Answer 1

Mullerian ducts, precursors to female internal structures; and a set of wolffian ducts, precursors to male internal structures.
Both also have undifferentiated gonads that are on their way to be coming either testes or ovaries.

Question 2

Precursors to female internal structures

Answer 2

Müllerian ducts

Question 3

Precursors to male internal structures

Answer 3

Wolffian ducts

Question 4

Sex-determining region on the Y chromosome. Gene that causes the primitive gonads to develop into testes

Answer 4

SRY gene

Question 5

Sperm-producing organs

Answer 5

Testes

Question 6

Testes-produced hormones that are more abundant in males

Answer 6

Androgens

Increase the growth of the testes, causing them to produce more androgens and so forth. That positive feedback cannot go on forever, but it lasts for a period of early development.

Androgens also cause the primitive wolffian ducts to develop into seminal vesicles and the vas deferens

Question 7

Saclike structures that store semen

Answer 7

Seminal vesicles

Question 8

A duct from the testes into the penis

Answer 8

Vas deferens

Question 9

The testes also produce this hormone, which causes the Müllerian ducts to degenerate. The final result is the development of a penis and scrotum.

Answer 9

Müllerian inhibiting hormone MIH

Question 10

Because females do not have the SRY gene, their gonads develop into ______ instead of testes, and their wolffian ducts degenerate. Because their ovaries do not produce Müllerian inhibiting hormone, MIH, female’s Müllerian ducts develop and mature into overtaxed, uterus, and the upper vagina

Answer 10

Ovaries

Question 11

Family of hormones that are more abundant in females

Answer 11

Estrogens

Question 12

Hormones that contain four carbon rings

Answer 12

Steroid hormones

Androgens and estrogens are steroid hormones, derived from cholesterol

Question 13

An androgen chemical

Answer 13

Testosterone

Question 14

A hormone in the estrogen family

Answer 14

Estradiol

Question 15

Steroid hormone that prepares the uterus for the implantation of a fertilized ovum and promotes the maintenance of pregnancy

Answer 15

Progesterone

Question 16

Steroids exert their effects in three ways:

Answer 16

First, they bind to membrane receptors, like neurotransmitters, exerting rapid effects

Second, they enter cells and activate certain kinds of proteins in the cytoplasm
Third, they bind to receptors that bind to chromosomes, where they activate or inactivate certain genes

Question 17

Describe the function of androgens and estrogens

Answer 17

Androgens promote the development of typically masculine features, such as facial hair. Estrogens promote typically female features, such as breast development. Androgens and estrogens also influence activity in many brain areas and alter the pattern of which neurons survive during early development.
Certain brain areas are relatively larger in men, on average, and others are relatively larger in women. These differences relate to gender and not to brain size.

Genes on the X and Y chromosomes produce sex differences in addition to those that we can trace to androgens and estrogens

Question 18

What does the SRY gene do?

Answer 18

The SRY gene, sex-determining region on the Y chromosome, causes the undifferentiated gonads of a mammal to develop into testes, which then produces testosterone and MIH (Müllerian inhibiting hormone) to direct development toward the male pattern

Question 19

How do sex hormones affect neurons?

Answer 19

Sex hormones, which are steroids, bind to receptors on the membrane, activate certain proteins in the cell’s cytoplasm, and activate or inactivate particular genes

Question 20

Long-lasting affects of a hormone that are present during a sensitive period early in development

Answer 20

Organizing effects

The most prominent organizing effects occur during a sensitive stage of early development – shortly before and after birth in rats and well before birth in humans – determining whether the body develops female or male anatomy. The surge of hormones at puberty also produces long lasting effects, such as breast development in women, facial hair in men, and male-female differences in the anatomy of certain parts of the hypothalamus

Question 21

Temporary effect of a hormone, which occurs at any time in life while the hormone is present

Answer 21

Activating effect

Question 22

Time early in development when experiences have a particularly strong and enduring influence

Answer 22

Sensitive period

Question 23

Describe the organizing effects during an early sensitive period, when hormones determine whether an embryo develops a male or female anatomy. In particular, describe the action of testosterone

Answer 23

Differentiation of the external genitals and several aspects of brain development depends mainly on the level of testosterone. A high level of testosterone causes the external genitals to develop the male pattern, and a low-level leads to the female pattern. Estradiol produces important effects on the internal organs, but it has little effect on the external genitals. The human sensitive period for genital formation is about the third and fourth months of pregnancy.

Question 24

Describe what happens when you inject female and male rats with testosterone or estrogen

Answer 24

In rats, testosterone begins masculinizing the external genitals during the last several days of pregnancy and first few days after birth and then continues masculinizing them at a declining rate for the next month.

A female rat that is injected with testosterone shortly before or after birth is partly masculinized, just as if her own body had produced the testosterone. Her clitoris grows larger than normal, and her behaviour is partly masculinized – she approaches sexually receptive females etc.

Injecting a genetic male with estrogens produces little effect on his external anatomy. However, he develops the female-typical pattern of anatomy and behaviour if he genetically lacks androgen receptor’s, if he is castrated, or if he is exposed to substances that block testosterone effects.

Question 25

Describe things that tend to feminize or demasculinized early development

Answer 25

Alcohol, marijuana, haloperidol, phthalates (chemicals common in many manufactured products), and cocaine. Aspirin to a slight extent, and estradiol-like compounds that are prevalent in the linings of plastic bottles and cans can produce abnormalities of the prostate gland in men

Question 26

What would be the genital appearance of a mammal exposed to high levels of both androgens and estrogens during early development? What if it were exposed to low levels of both?

Answer 26

A mammal exposed to high levels of both male and female hormones will appear male. One exposed to low levels of both will appear female. Genital development depends mostly on the presence or absence of androgens and is nearly independent of estradiol levels.

Question 27

From the standpoint of protecting a male foetuses sexual development, what are some drugs that a pregnant woman should avoid?

Answer 27

Pregnant women should avoid alcohol, marijuana, haloperidol, phthalates, and cocaine because these drugs interfere with male sexual development. Even aspirin and the chemicals lining bottles and cans produce mild abnormalities. Obviously, the results depend on both quantities and timing of exposure to these chemicals

Question 28

Area in the anterior hypothalamus that is larger in males than in females and contributes to control of male sexual behaviour

Answer 28

Sexually dimorphic nucleus

Question 29

Protein that binds with estradiol in the bloodstream of immature mammals

Answer 29

Alpha-fetoprotein

Question 30

In rodents, testosterone exerts much of its organizing effect through a surprising route:

Answer 30

After testosterone enters a neuron in early development, it is converted to estradiol. An enzyme found in the brain can aromatize testosterone into estradiol. Other androgens that cannot be aromatized into estrogens are less effective in masculinizing the hypothalamus.

Question 31

Why does a female rodents own estradiol fail to masculinize her hypothalamus given the fact that testosterone is converted to estradiol in male rodents?

Answer 31

During the early sensitive., Immature mammals have a protein called alpha-fetoprotein, which is not present in adults. This protein in rodents binds with estradiol and prevents it from entering cells, where it could produce masculinizing effects. Because testosterone does not bind to alpha-fetoprotein, it can enter neurons, where enzymes convert it into estradiol. That is, testosterone is a way of getting estradiol to its receptors when estradiol circulating in the blood is inactivated

Question 32

How would the external genitals appear on a genetic female rat that lacked alpha-fetoprotein?

Answer 32

A female that lacked alpha-fetoprotein would be masculinized by her own estradiol, as researchers have in fact demonstrated

Question 33

What evidence most directly links children’s toy play to prenatal hormones?

Answer 33

Girls whose mothers had higher testosterone levels during pregnancy tend to play with boys toys more than the average for other girls. Boys whose mothers had higher phthalate exposure (which inhibit testosterone production) tend to play with boys’ toys less than the average for other boys

Question 34

Describe the activation effects of sex hormones in rodents

Answer 34

For rodents, sex hormones facilitate sexual activity. Testosterone is essential for male sexual arousal, and a combination of estradiol and progesterone is the most effective combination for females. Arousal also depends on previous experience.

Sex hormones activate sexual behaviour partly by enhancing sensations. Estrogens increase the sensitivity of pudendal nerve, which transmits tactile stimulation from the vagina and cervix to the brain. Testosterone increases sensitivity in the penis.

Erection depends partly on the fact that testosterone increases the release of nitric oxide, which increases blood flow to the penis.

Testosterone and oestradiol prime the MPOA and several other brain areas to release dopamine, and the MPOA neurons release dopamine strongly during sexual activity.

In moderate concentrations, dopamine stimulates mostly type D1 and D5 receptors, which facilitate erection of the penis in the male and sexually receptive postures in the female. In higher concentrations, dopamine stimulates type D2 receptors, which leads to orgasm.

Where is dopamine stimulate sexual activity, the neurotransmitter serotonin inhibits it, in part by blocking dopamine release

Question 35

By what mechanism do testosterone and estradiol affect the hypothalamus areas responsible for sexual behavior?

Answer 35

Testosterone and estradiol prime hypothalamic cells to be ready to release dopamine. They also increase sensitivity in the genital area

Question 36

The inability to have an erection

Answer 36

Impotence

Question 37

Describe the activating effects of the sex hormone testosterone in humans

Answer 37

Among men, levels of testosterone correlate positively with sexual arousal and the drive to seek sexual partners.
On average, married men and men living with a woman in a committed relationship have lower testosterone levels than single, unpaired men of the same age- One study found that men’s testosterone levels do not change after marriage. Instead, men with lower testosterone levels were more likely to marry than were men with high testosterone levels.

Other studies found that single women had higher testosterone levels than women with a long-term partner. Both men and women with high testosterone levels are more likely than average to seek additional sex partners, even after they marry or establish a long-term relationship. Important to note that data is correlational

Question 38

Decreases in testosterone levels generally decrease male sexual activity. However, low testosterone is not the usual basis for ______, The inability to have an erection. The most common cause is impaired blood circulation, especially in older men. Other common causes include neurological problems, reactions to drugs, and psychological tension

Answer 38

Impotence

Question 39

What is the explanation for why married men tend to have lower testosterone levels than single men of the same age?

Answer 39

Men with lower testosterone levels are more likely to get married than are men with higher testosterone levels

Question 40

A periodic variation in hormones and fertility over the course of about 28 days

Answer 40

Menstrual cycle

Question 41

Chemical released from the anterior pituitary; promotes the growth of a follicle in the ovary

Answer 41

Follicle-stimulating hormone FSH

Question 42

Hormone released from the anterior pituitary that causes the follicle to release an ovum

Answer 42

Luteinizing hormone LH

Question 43

Describe the hormonal processes that control women’s menstrual cycles

Answer 43

After the end of a menstrual period, the anterior pituitary releases follicle-stimulating hormone FSH, which promotes the growth of a follicle in the ovary. The follicle nurtures the ovum (egg cell), and produces several types of estrogen, including estradiol.

Toward the middle of the menstrual cycle, the follicle builds up more and more receptors to FSH, so even though the actual concentration of FSH in the blood is decreasing, it’s effects on the follicle increase. As a result, the follicle produces increasing amounts of estradiol. Increased release of estradiol causes an increased release of FSH as well as a sudden surge in the release of luteinizing hormone LH from the anterior pituitary.
FSH and LH combine to cause a follicle to release an ovum.

The remnant of the follicle, now called
the corpus luteum, releases the hormone progesterone, which prepares the uterus for the implantation of a fertilized ovum. Progesterone also inhibits the further release of LH.

Toward the end of the menstrual cycle, the levels of LH, FSH, estradiol, and progesterone all decline. If the ovum is not fertilized, the lining of the uterus is cast off through menstruation, and the cycle begins again.
If the ovum is fertilized, the levels of estradiol and progesterone increase gradually during pregnancy.

Question 44

One consequence of high estradiol and progesterone levels during pregnancy is fluctuating activity at the serotonin 3 receptor, which is responsible for:

Answer 44

Nausea

Question 45

Describe the effects of birth-control pills

Answer 45

Birth control pills prevent pregnancy by interfering with usual feedback cycle between the ovaries and the pituitary.

The most widely used birth control pill, the combination pill, containing oestrogen and progesterone, prevents the surge of FSH and LH that would otherwise release and ovum. The estrogen-progesterone combination also thickens the mucus of the cervix, making it harder for a sperm to reach the egg, and prevents an ovum, if released, from implanting in the uterus

Question 46

Time around the middle of the menstrual cycle of maximum fertility and high estrogen levels

Answer 46

Periovulatory period

According to studies, women initiate more sexual activity during this period than at other times of the month, rate erotic videos as more pleasant and arousing, and choose more masculine looking men for short term relationships

Question 47

At what time in a woman’s menstrual cycle do her estradiol levels increase? When are they lowest?

Answer 47

Estrogen levels increase during the days leading up to the middle of the menstrual cycle. They are lowest during and just after menstruation

Question 48

Hormone released by posterior pituitary; important for sexual and parental behavior’s.

Stimulate contractions of the uterus during delivery of a baby, and it stimulates the memory gland to release milk. Also released during and after sexual pleasure

Answer 48

Oxytocin

Induces relaxation shortly after orgasm.
Strong release of oxytocin facilitates formation of pair bonds between mating partners, and is also related to the formation of a pair bond between mother and infant.
Facilitates other social behaviours – recognizing familiar faces more accurately, trust the trustworthy more and not those who seem competitive and aggressive.

Question 49

What behavioural change occurs after orgasm, and which hormone is responsible?

Answer 49

Anxiety decreases after orgasm because of release of the pituitary hormone oxytocin

Question 50

Describe the endocrine influences on parental behaviours

Answer 50

The role of hormones is less central for humans, and is critical for maternal behaviour in other species.

After a mother rat delivers her babies, she increases her secretion of oestradiol and prolactin, while decreasing production of progesterone. Prolactin is necessary for milk production and certain aspects of maternal behavior, such as retrieving the young when they wander away from the nest. It also inhibits sensitivity to leptin, enabling the mother to eat far more than usual.
Late in pregnancy, the female rodent brain increases its sensitivity to oestradiol in the areas responsible for maternal behavior, which increases the mothers attention to their young after delivery. Hormones increase activity in the medial preoptic area and anterior hypothalamus, which are also necessary for rats maternal behaviour.

Vasopressin: A key hormone in parental behavior, is synthesized by the hypothalamus and secreted by the posterior pituitary gland. Important for social behaviour in many species, partly by facilitating olfactory recognition of other individuals. Establishes long-term pair bonds between males and females and helps males to rear their young.
Although rodent maternal behaviour depends on hormones for the first few days, it becomes less dependent later. A female that has never been pregnant left with some baby rats ignores them at first but gradually becomes more attentive.

Because pheromones of the infant stimulate aggressive behaviours that interfere with maternal behavior, hormones compensate for the mothers lack of familiarly with the young in the early phase of motherhood by overriding competing impulses. In the later phase, experience maintains the maternal behaviour even though the hormones start

Question 51

What factors are responsible for maternal behaviour shortly after rats give birth? What factors become more important in later days?

Answer 51

The early stage of rats’ maternal behaviour depends on a surge in the release of the hormones prolactin and estradiol. A few days later, her experience with the young decreases the vomeronasal responses that would tend to make her reject them. Experience with the young maintains maternal behaviour after the hormone levels begin to drop

Question 52

Tendency for a gene to spread in the population if it makes individuals more appealing to the opposite sex

Answer 52

Sexual selection

Question 53

Describe an evolutionary interpretation of why more men than women seek opportunities for casual sexual relationships with many partners

Answer 53

From the evolutionary standpoint of spreading ones genes, men can succeed by either of two strategies: be loyal to one woman and devote your energies to helping her and her babies, or meet with many women and hope that some of them can raise your babies without your help. In contrast, a woman can have no more than one pregnancy per nine months, regardless of her number of sex partners.

Objections: a woman does sometimes gain from having multiple sex partners. Researchers have no direct evidence that genes influence people’s preferences for one mate or many

Question 54

Describe evolutionary interpretations of what men and women seek in a mate

Answer 54

Almost all people seeking a romantic partner prefer someone who is healthy, intelligent, honest, and physically attractive.

Women have some additional interests that are less common for men: more likely to prefer a mate who is likely to be a good provider.
Evolutionary interpretation: while a woman is pregnant or taking care of a small child, she needs help getting food and other requirements.

Women are also more likely to reject a man because of his smell. One possible reason is that body odour relates to some of the same genes that control the immune system, known as the major histocompatibility complex. A woman tends to be less sexually responsive to a man whose immune genes, and therefore body odour, are similar to her own

Men tend to have a stronger preference for a young partner: evolutionary explanation – young women are likely to remain fertile longer than older women are

Question 55

Describe evolutionary interpretations of differences in jealousy

Answer 55

Traditionally, in most cultures, men have been more jealous of women’s infidelities then women have been of men’s infidelities.
Evolutionary interpretation: if a man is to pass on his genes, the key point in evolution, he needs to be sure that the children he supports are his own. An unfaithful wife threatens that certainty. A woman knows any children she bears are her own, so she does not have the same worry

Question 56

What evolutionary advantage is suggested for why women are more interested in men’s wealth and success than men are interested in women’s wealth?

Answer 56

During pregnancy and early childcare, a female is limited in her ability to get food and therefore prefers a male partner who can provide for her. A healthy male is not similarly dependent on a female

Question 57

Sex with which a person identifies

Answer 57

Gender identity

Question 58

People whose sexual development is intermediate or ambiguous

Answer 58

Intersexes

Question 59

Individual who appears to be a mixture of male and female anatomies

Answer 59

Hermaphrodite

Question 60

The overdevelopment of the adrenal glands from birth

These people develop an intermediate appearance because of an atypical hormone pattern. A genetic male with low levels of testosterone or a deficiency of testosterone receptors may develop a female or intermediate appearance. A genetic female who is exposed to more testosterone than the average female can be partly masculinized.

Answer 60

Congenital adrenal hyperplasia CAH

Ordinarily, the adrenal gland has a negative feedback relationship with the pituitary gland. The pituitary secretes adrenocorticotropic hormone ACTH, which stimulates the adrenal gland. Cortisol, one of the hormones from the adrenal gland, feeds back to decrease the release of ACTH. Some people have a genetic limitation in their ability to produce cortisol. Because the pituitary fails to receive much cortisol as a Feedback signal, it continues secreting more ACTH, causing the adrenal gland to secrete larger amounts of its other hormones, including testosterone. In a genetic male, the extra testosterone causes no apparent difficulty. However, genetic females with this condition develop various degrees of masculinization of their external genitals.

Question 61

What is a common cause for a genetic female (XX) to develop a partly masculinized anatomy?

Answer 61

If a genetic female is genetically deficient in her ability to produce cortisol, the pituitary gland does not receive negative feedback signals and therefore continues stimulating the adrenal gland. The adrenal gland then produces large amounts of other hormones, including testosterone, which masculinizes development

Question 62

If a genetic female is exposed to extra testosterone during prenatal development, what behavioural effect is likely?

Answer 62

A girl who is exposed to extra testosterone during prenatal development is more likely than most other girls to preferred boy-typical toys

Question 63

Condition in which individuals with an XY chromosome pattern have the genital appearance of a female

Answer 63

Testicular feminization or androgen insensitivity

Although such individuals produce normal amounts of androgens, including testosterone, they lack the receptor that enables androgen to activate genes in a cells nucleus. Consequently, the cells are insensitive to androgens, and development proceeds as if the level of testosterone and similar hormones was low.

Question 64

What would cause a genetic male (XY) to develop a partly feminized external anatomy?

Answer 64

A genetic male with a gene that prevents testosterone from binding to its receptors will develop an appearance that partly or completely resembles a female

Question 65

When “girls” reached puberty and drew a penis and scrotum in certain case studies such as in the Dominican republic, what happened to their gender identity?

Answer 65

Most changed their gender identity from female to male

Question 66

Describe behavioural and anatomical differences in sexual orientation

Answer 66

On average, heterosexual men are slightly taller and heavier than homosexual men.

People who are different sexual orientation also differ in several behaviours that are not directly related to sex: more men than women give directions in terms of distances and north, south, east, or west. Women are more likely to describe landmarks. Gay men also tend to use landmarks and are better than heterosexual men at remembering landmarks.
Peoples inhibition is ordinarily stronger in men than women – homosexual women are slightly shifted in the male direction compared to heterosexual women

Question 67

For which kind of twin pair is the concordance for sexual orientation greatest?

Answer 67

Monozygotic twins have higher concordance than dizygotic twins. Note the importance of stating this point correctly: do not say that homosexuality is more common in monozygotic then dizygotic twins. It is the concordance that is greater – that is, the probability that both twins have the same sexual orientation

Question 68

Describe four hypotheses about whether certain genes promote a homosexual orientation

Answer 68

Genes for homosexuality are maintained by kin selection

Genes that produce homosexuality in males produce advantageous effects in their sisters and other female relatives, increasing their probability of reproducing and spreading the genes

Certain genes lead to homosexuality in men homozygous for the gene that produce reproductive advantages in men heterozygous for the gene

Homosexuality relates to the activation or inactivation of jeans. It is possible for environmental events to attach a methyl group CH3 to a gene and inactivate it. A parent can pass the inactivation of a gene to the next generation. Conceivably, this mechanism might produce a significant amount of homosexuality without relying on the spread of a gene that promotes homosexuality

Question 69

It seems difficult to explain how a gene could remain at a moderately high frequency in a population if most men with the gene do not reproduce. How would the hypotheses about inactivation buy a methyl group help with the explanation?

Answer 69

According to this hypothesis, some unknown event in the environment can attach a methyl group to some unidentified gene, inactivating the gene. That gene could be passed to the next generation, producing evidence for a hereditary effect, even though there is no “gene for homosexuality.” If this event of attaching a methyl group to that gene happens often enough, the result could be a moderately high prevalence of homosexuality, even if men with the inactivated gene seldom reproduce

Question 70

Describe possible prenatal influences on sexual orientation

Answer 70

The mothers immune system – several studies report that the probability of a homosexual orientation is slightly higher among men who have older brothers. The key is how many previous times the mother gave birth to a son. The most prominent hypothesis is that a mothers immune system sometimes reacts against a protein in a son and then attacks subsequent sons enough to alter their development.

Stress on the mother during pregnancy – research has shown that prenatal stress alters sexual development in laboratory animals

Alcohol

Question 71

By what route might having an older brother increase the probability of male homosexuality?

Answer 71

Having an older brother might increase the probability of male homosexuality by altering the mothers immune system in the prenatal environment. The effect of the older brother does not depend on growing up in the same home

Question 72

How might stress to a pregnant rat alter the sexual orientation of her male offspring?

Answer 72

Evidently, stress increases the release of endorphins in the hypothalamus, and very high endorphin levels can block the effects of testosterone

Question 73

Describe the influence of brain anatomy in sexual orientation

Answer 73

Homosexual men are shifted partly in the female-typical direction for some brain structures but not others. It is similar for homosexual women’s brains, which are slightly shifted in the male direction in some ways but not others.

Homosexual males resemble heterosexual females in the following ways:
left and right hemispheres of the cerebral cortex are of nearly equal size compared to heterosexual males where the right hemisphere is a few percent larger.
The left amygdala has more widespread connections than the right amygdala, whereas in heterosexual males the right amygdala has more widespread connections.
The anterior commisure is larger than in heterosexual men.
The suprachiasmatic nucleus is larger in homosexual men than in heterosexual men

The most widely cited research concerns the third interstitial nucleus of the anterior hypothalamus INAH-3:
Generally more than twice as large in heterosexual men as in women. Research has found that the mean volume of INAH-3 is larger in heterosexual men than in heterosexual women or homosexual men, Who were about equal in this regard

Question 74

In LeVay’s study, what evidence argues against the idea that INAH-3 volume depends on AIDS rather than sexual orientation?

Answer 74

The average size of INAH-3 was about the same for heterosexual men who died of aids and those who died of other causes. One homosexual man who died of other causes had about the same size INAH-3 as heterosexual men who died of AIDS