copyright © 2008 pearson allyn & bacon inc.1 chapter 9 reproductive behavior this multimedia...

Copyright © 2008 Pearson Allyn & Bacon Inc.1

Chapter 9

Reproductive Behavior

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• Chapter 9 Outline

• Sexual Development

• Hormonal Control of Sexual Behavior

• Neural Control of Sexual Behavior

• Parental Behavior



• Sexually _________________behavior• A behavior that has different forms or that occurs with

different probabilities or under different circumstances in _____________________.

Courting behavior

Mating behavior

Parental behavior

Aggression



• Sexual development

• ______________:• A mature reproductive cell; a sperm or ovum.• __________: contains one member of a pair of ___

chromosomes

• Sex chromosome:• The X and Y chromosomes, which determine an

organism’s gender. Normally, females are XX and males are XY.


Gender is determined by the ___ chromosome in the sperm.



• Development of the sex organs

• __________• An ovary or testis.

• ____• The gene of the Y chromosome whose produce

instructs the undifferentiated fetal gonads to develop into testes.

• Natures impulse is to build a female body unless instructed to do otherwise.

• Exposure to sex hormones _________________ is responsible for sexual dimorphism.

• The immature gonad is capable of becoming female (ovary) or male (testes).




• Development of the sex organs: hormomes have both organizational and activational effects

• _____________effect (of hormone)• The effect of a hormone on tissue differentiation and

development. These effects are ___________.

• ______________effect (of hormone)• 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.



• Internal sex organs: • The immature gonad has both a Müllerian and

Wolffian system

• _______________system• The embryonic precursors of the female internal sex

organs.

• ________________system• The embryonic precursors of the male internal sex

organs.



• Internal sex organs

• Anti-Müllerian hormone• A peptide secreted by the fetal testes that inhibits the

development of the Müllerian system, which would otherwise become the ________________________.

• 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.



• Internal sex organs

• _____________• A male sex steroid hormone. Testosterone is the

principal mammalian androgen.

• _______________effect• An effect of a hormone present early in development

that promotes the later development of anatomical or behavioral characteristics typical of males.

• _______________• The principal androgen found in males.



• Internal Sex Organs

• Dihydrotestosterone• An androgen, produced from testosterone through the

action of the enzyme 5 reductase.

• ____________________________• A condition caused by a congenital lack of functioning

androgen receptors; in a person with XY sex chromosomes, causes development of a female with testes but no internal sex organs. The external genitalia are _______________________________________.


• Sexual Development• Internal sex organs

• Persistent Müllerian duct syndrome• A condition caused by a congenital lack of

anti-Müllerian hormone or receptors for this hormone;

in a male, causes development of ________________________________________. The presence of the female anatomy disrupts the functioning of the male anatomy.

• ___________________• The presence of only one sex chromosome (X0);

characterized by lack of ovaries but otherwise normal female sex organs and genitalia. (Usually the result of a defective sperm.)



• _______________: The onset of puberty is governed by the hypothalamus by the initiation of the secretion of gonadotropin-releasing hormone.

• _______________________________

A hypothalamic hormone that stimulates the anterior pituitary gland to secrete gonadotropic hormone.

• ______________________hormone• A hormone of the anterior pituitary gland that has a

stimulating effect on cells of the gonads.



• Sexual maturation (2 gonadotropic hormones are secreted by the pituitary)

• _______________________• The hormone of the anterior pituitary gland that causes

development of an ovarian follicle and the maturation of it as an ovum.

• __________________• A hormone of the anterior pituitary gland that causes

ovulation and development of the ovarian follicle into a corpus luteum.

• In males these same hormones cause the ____________________________________________



• Sexual maturation (Female)

• _______________• The principal estrogen of many mammals, including

humans.

• ________________• A class of sex hormones that causes maturation of the

female genitalia, growth of breast tissue, and development of other physical features characteristic of females.



• Sexual maturation (Male)

• ____________________• The principal androgen of many mammals, including

humans.

• ______________• A class of sex hormones that causes maturation of the

male genitalia, growth of facial and body hair, lowering of the voice, muscle development, and development of other physical features characteristic of males.



• Hormonal control of female reproductive cycles

• __________________• The female reproductive cycle of most primates,

including humans, characterized by growth of the

lining of the uterus, ovulation, development of a

corpus luteum, and (if pregnancy does not occur) menstruation.



• Hormonal control of female reproductive cycles

• _________________• The female reproductive cycle of mammals other than

primates.

• ___________________• A cluster of epithelial cells surrounding an oocyte

which develops into an ovum.



• Hormonal control of female reproductive cycles• Menstrual or estrus cycles

• ____________________• A cluster of cells that develops from the ovarian follicle

after ovulation; secretes estradiol and 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.

• FSH stimulates the growth of an ovarian follicle (a sphere of cells surrounding each ovum).

• The follicle secretes estradoil which in turn causes the pituitary to secrete LH.

• The surge in LH causes _____________.

• Following ovulation the ruptured follicle becomes the corpus luteum which secretes progesterone and estradiol which promote pregnancy.



• Hormonal Control of Sexual Behavior of Laboratory Animals• Males

• Intromission, pelvic thrusting, ejaculation

• ________________• A period of time after a particular action (for example,

an ejaculation by a male) during which that action cannot occur again.

• ___________________• The restorative effect of introducing a new female sex

partner to a male that has apparently become “exhausted” by sexual activity.


• Hormonal Control of Sexual Behavior of Laboratory Animals

• Females

• ______________• A sexual spinal reflex seen in many four-legged

animals. Female mammals; arching of the back in response to approach of a male or to the touch of

the flanks, which elevates the hindquarters.

In the absence of this reflex intromission is no possible.

No recreational (non-reproductive) mating behavior.


Castrated at birth


• Organizational Effects of Androgens on Behavior:Masculinization and Defeminization

• Effects of pheromones

• __________________• A chemical released by one animal that affects the

behavior or physiology of another animal; usually smelled or tasted.

• ____________________• The slowing and eventual cessation of estrous cycles

in groups of female animals that are housed together; caused by a pheromone in the animal’s urine.




• ____________________• The synchronization of the menstrual or estrous cycle

of a group of females, which occurs only in the presence of a pheromone in a male’s urine.

• ________________________• The earlier onset of puberty seen in female animals

that are housed with males; caused by a pheromone in the male’s urine.



• Effects of Pheromones

• ___________________• Termination of pregnancy caused by the odor of a

pheromone in the urine of a male other than the one that impregnated the female.

• _________________________• A sensory organ that detects the presence of certain

chemicals, especially when a liquid is actively sniffed; mediates the effects of some pheromones.




• ____________________• A neural structure located in the main olfactory bulb

that receives information from the vomeronasal organ.

• Pheromones in humans

• Menstrual synchronization• Essence of Genieve• May function to ____________________• Androstadienone (AND) in male sweat induces

alertness and _________________in women, but not in men. Could play a role in bonding, mate attraction and mate recognition.



Female initiation promotes conception



• Prenatal androgenization of genetic females

• _______________________________ (CAH)• A condition characterized by hypersecretion of

androgens by the adrenal gland; in females, causes masculinization of the external genitalia.

• Increase in bisexual and homosexual orientation.• Increase play with male-typical toys.

Revision 2006 PSB

Sexual Orientation

Sexual orientation refers to a person’s preference for emotional and sexual relationships with individuals of the

same sex, other sex and/or either sex; an enduring sexual attraction toward members of either one’s own gender (homosexual orientation) or the other gender

(heterosexual orientation)

HomosexualHeterosexual

Bisexual

Revision 2006 PSB

Sexual Preference

• About 4% of the adult population is homosexual – sexual behavior is directed towards members of one’s own gender.

• Neuronal factors: LeVay (1991) found that one region of the hypothalamus was two times larger in hetersexual males compared to that for homosexual males. In male monkeys the surgical destruction of these cells reduced the monkeys interest in females, but did not reduce _____________.

Revision 2006 PSB

Sexual MotivationOrigins of Homosexuality

• Identical twins have highest concordance (similarity) rates for sexual orientation compared to fraternal twins and adoptive siblings. • Same pattern exists for males and females.

• This suggests that sexual orientation is influenced by genes.

Revision 2006 PSB

Bailey & Pillard (1991; 1992)

• Male homosexuality concordance rates:

52% identical twin

22% fraternal twin

11% adopted brother

Female homosexuality concordance rates:

48% identical twin

16% fraternal twin

6% adopted sister

Revision 2006 PSB

Origins of Sexual Orientation

Homosexuality is more likely to be based on biological factors like differing brain centers, genetics, parental hormone exposure, than

_________________________________.

Homosexual parents

Cynthia Johnson/ T

ime m

agazine

Revision 2006 PSB

The Homosexual Man’s Brain

The size of the anterior hypothalamus is smaller (LeVay, 1991) and anterior

commissure is larger (Allen & Gorski, 1992) in homosexual men.

AnteriorHypothalamus

AnteriorCommissure

http

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ww

.msu

.edu

Revision 2006 PSB

Hormones & Sexual Orientation

Prenatal hormones affect sexual orientation during _______________ of fetal development.

1. Animals: Testosterone exposure to fetus results in females (sheep) showing homosexual behavior.

2. Humans: Female hormone exposure to male or female fetus (human) results in attraction to males.

Heterosexualmale

Homosexual Heterosexualfemale

Revision 2006 PSB

Sexual Orientation

• Recent data suggests that male homosexuality is more common among the male relatives of the men’s _________ side of the family. The gene for sexual orientation is located on the x chromosome – the only chromosome inherited exclusively from one’s __________.

• Area Xq28 is believe to most strongly influence sexual orientation.

Revision 2006 PSB

Changing Attitudes



• Males

• ___________________ (MPA)• An area of cell bodies just rostral to the hypothalamus;

plays an essential role in male sexual behavior.



• Males

• 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 appears to depend on ________________________________________.



• Males

• Nucleus paragigantocellularis (PGi)• A nucleus of the medulla that receives input from the

medial preoptic area and contains neurons whose axons form synapses with motor neurons in the spinal cord that participate in sexual reflexes in males.

• The PGi inhibits sexual reflexes by releasing serotonin on spinal nuclei. The MPA pathway must act to suppress PGi inhibition for sexual reflexes to occur.

• SSRI drugs emulate PGi inhibition and depress ________________.



• Females

• ____________________________________(VMH)• A large nucleus of the hypothalamus located near the

walls of the third ventricle; plays an essential role in female sexual behavior.

• Pair bonding

• Increase levels of vasopressin and oxytocin are observed in_____________, relative to polygynous ones, and injections of vasopressin can transform polygynous rodents into _____________pair bonding.

• Biologically fitness is determined by procreation, and parental behavior is critical for reproductive success.

• Maternal behavior is established by a hormonal sequence associated with reproduction.


• Virgin females injected with hormones that duplicates this sequence will rapidly begin to display maternal care for pups.

• Pair bonding between mother and offspring appear to involve ___________________.

• fMRI studies show that when mothers are shown photos of their infants that brain centers that contain receptor sites for vasopressin and oxytocin are activated, as well as brain regions involved in ________________.


• Summary

• Male and female behaviors are not simply the result of socialization.

• The case of Brenda described by Carlson suggests that the infant’s brain was masculinized by early exposure to androgens and Brenda was unable to adjust to the female body and role expectations that had been surgically and chemically constructed for her.


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