1. Wood1.1 Credits lightning ©istockphoto.com/Soubrette
background texture
©istockphoto.com/Hedda Gjerpen
person rock climbing
©istockphoto.com/Greg Epperson
Wood1.1

2. Topics 13.1 Neuroendocrine System 13.2
Hormones and Sexual Development of the Body
13.3
Hormones and Sexual Development of Brain and Behavior
13.4
Three Cases of Exceptional Human Sexual Development
13.5
Effects of Gonadal Hormones on Adults
13.6
Neural Mechanisms of Sexual Behavior
13.7
Sexual Orientation and Sexual Identity
Credits
lightning
©istockphoto.com/Soubrette
background texture
©istockphoto.com/Hedda Gjerpen
Wood1.

3. Developmental and Activational Effects of Sex Hormones
Developmental (or “organizational”) – influencing the development of anatomical, physiological, and behavioral characteristics that differentiate the sexes
Activational – triggering reproduction-related behavior in mature individuals
Adolescent surges have both developmental and activational effects
L11.12

4. Neuroendocrine System: Glands
Exocrine – release chemicals into ducts which carry them to their targets
Sweat glands, for example
Endocrine – ductless; release hormones directly into the circulatory system
Only organs whose primary function is hormone release are referred to as endocrine glands
L12.30

5. Neuroendocrine System: Glands
FIGURE 13.1:
The endocrine glands

6. Neuroendocrine System: Glands
Male testes produce sperm cells
Female ovaries produce ova
Sperm and ova each have 23 chromosomes
Fertilization
Sperm cell + ovum = zygote
23 pairs of chromosomes
X and Y – sex chromosomes
XX = female, XY = male
Wade3.34

7. Classes of Hormones Amino acid derivatives
Epinephrine, for example (adrenal medulla)
Peptides and proteins
Short and long chains of amino acids
Steroids
Synthesized from cholesterol (fat)
Fat-soluble – able to enter cells and bind to receptors in cytoplasm or nucleus
Credit
person thinking
©istockphoto.com/akurtz

8. Sex Steroids Released by gonads Androgens - e.g., testosterone
Estrogens - e.g., estradiol
Adult testes release more androgens and ovaries more estrogens
Progestins – also present in both sexes
Progesterone prepares uterus and breasts for pregnancy
Adrenal cortex – also releases sex steroids
L11.16

9. Hormones of the Pituitary
“Master gland”
Tropic hormones influence the release of hormones by other glands
Posterior pituitary – hormones synthesized in the hypothalamus
Anterior pituitary – tropic hormones
Wood1.
Credit
brain
©istockphoto.com/Stephen Kirklys

10. Hormones of the Pituitary
FIGURE 13.2:
A midline view of the posterior and anterior pituitary and surrounding structures

11. Cyclic vs. Steady Gonadal Hormone Levels
Female hormones go through a 28-day cycle, the menstrual cycle
Male hormone levels are constant
Anterior pituitary activity is controlled by the hypothalamus
The hypothalamus determines whether hormone levels cycle
L7.1

12. Neural Control of the Pituitary
Bird research was first to implicate the control over pituitary function by the nervous system
Light/dark cycling and breeding changed hormone release
Lesion and stimulation experiments established the hypothalamus as the regulator of the anterior pituitary
Did not explain how the signal was mediated as the anterior pituitary is not “connected” to the hypothalamus by neurons
The human brain
Credits
brain
©istockphoto.com/Stephen Kirklys
neuron
©istockphoto.com/ktsimage
Wood1. 12

13. Control of the Pituitary by the Hypothalamus
Posterior pituitary – neural input from hypothalamus
Vasopressin – antidiuretic hormone
Oxytocin – labor and lactation
Synthesized in hypothalamic paraventricular and supraoptic nuclei
These nuclei have terminals in the posterior pituitary
Anterior pituitary – hypothalamopituitary portal system carries hormones from the hypothalamus to the anterior pituitary

14. Control of the Pituitary by the Hypothalamus
FIGURE 13.4:
Control of the anterior and posterior pituitary by the hypothalamus

15. Discovery of Hypothalamic Releasing Hormones
Thyrotropin-releasing hormone first isolated from the hypothalamus of sheep and then pigs
Triggers the release of thyrotropin from the anterior pituitary
Thyrotropin then stimulates release of hormones from the thyroid gland
Credit
book
©istockphoto.com/Carmen Martínez Banús 15

16. Regulation of Hormone Levels
Neural
All endocrine glands (except the anterior pituitary) receive neural signals
From cerebral or autonomic neurons
Hormonal
Tropic hormones, negative feedback
Nonhormonal chemicals
Glucose, Ca2+, Na+
Pulsatile Hormone Release:
Hormones tend to be released in pulses
Leads to often large minute-to-minute fluctuations in levels of hormones
L12.23

17. Summary Model of Gonadal Endocrine Regulation
FIGURE 13.5:
A summary model of the regulation of gonadal hormones

18. Hormones and Sexual Development of the Body
Humans are dimorphic – exist in two forms
Genetic information on the sex chromosomes normally determines male or female development
Wood1.

19. Fetal Hormones and Development of Reproductive Organs: Gonads
Initially there is a primordial gonad
Cortex – Potential to be an ovary
Medulla – potential to be a testis
If XY, the Sry gene on the Y chromosome triggers the synthesis of Sry protein
If no Sry protein present, cortex develops into ovary
L10.11

20. Fetal Hormones and Development of Reproductive Organs: Gonads
FIGURE 13.6:
The development of an ovary and a testis from the cortex and the medulla, respectively, of the primordial
gonadal structure that is present 6 weeks after conception.

21. Fetal Hormones and Development of Reproductive Organs: Internal Reproductive Ducts
Both sexes begin with two sets of reproductive ducts
Wolffian system – male – seminal vessicles, vas deferens
Mullerian system – female – uterus, vagina, fallopian tubes
Third prenatal month: differentiation of ducts
Testes produce testosterone and Mullerian-inhibiting substance
Wolffian system develops, Mullerian degenerates, testes descend
No testes – no testicular hormones
Mullerian system develops, Wolffian degenerates
L10.11

22. Internal Reproductive Ducts
FIGURE 13.7:
The development of the internal ducts of the male and female reproductive systems from the Wolffian and Müllerian systems, respectively

23. External Reproductive Organs
External reproductive structures – genitalia – develop from one bipotential precursor
Differentiation occurs in second month
Testosterone produces male structures
Without testosterone, female structures develop
Wade3.24

24. Personal space Body language Explicit acts
Puberty
Fertility achieved
Secondary sex characteristics develop
Features unrelated to reproduction that distinguish sexually mature men and women
Increase in release of anterior pituitary hormones
Growth hormone – acts on bone and muscle
Gonadotropic hormone
Adrenocorticotropic hormone
Relative levels of androgens and estrogens determine whether male or female features develop
Androstenedione – androgen necessary for the growth of axillary (underarm) and pubic hair in females (more evidence against mamawawa)
Personal space
Body language
Explicit acts
L11.13

25. Sex Differences in the Brain
Pfeiffer first discovered a sex difference in mammalian brain function
Pfeiffer (1936) gonadectomized and implanted gonads in neonatal rats:
Transplant of testes to males or females causes steady (male) gonadotropin release pattern
Perinatal androgens lead to male pattern
Gonadectomy causes cyclic (female) gonadotropin release pattern
L10.17

26. Aromatization Hypothesis
Sex steroids are all derived from cholesterol and are readily converted from one to the other
Aromatized testosterone becomes estradiol
Evidence suggests that estradiol masculinizes the brain, at least in rodents
Credit
book
©istockphoto.com/Carmen Martínez Banús 26

27. Evidence that Estradiol Masculinizes the Neonatal Brain
Neonatal injections of estradiol masculinize
Dihydrotestosterone can’t be converted to estradiol – doesn’t masculinize
Alpha fetoprotein deactivates circulating estradiol but does not cross the blood-brain-barrier
Blocking aromatization or estradiol receptors interferes with masculinizing effects of testosterone
L7.1

28. Mother’s Estradiol Doesn’t Masculinize Female Brains
In female rodents, Alpha fetoprotein in blood during perinatal period …
Protects the female brain from estradiol
Binds to circulating estradiol, so none gets to the brain
In male rodents, testosterone enters the brain and then is converted to estradiol
In humans, aromatization is apparently not necessary for testosterone to masculinize brain
Credit
hand holding rat
©iStockphoto.com/sidsnapper

29. Modern Perspectives on Sexual Differentiation of the Mammalian Brain
No single mechanism can account for the development of sexual dimorphisms of mammalian brains:
Aromatase is only required for testosterone effects on masculinization in some areas of the brain
Female brain development may not automatically occur in absence of estrogens
Various dimorphisms emerge at different stages under different influences
Sex chromosomes influence brain development independent of their effect on hormones
Studies with gene knockout mice indicate that estradiol plays an active role in the female program of brain development
Wade3.38

30. Perinatal Hormones and Behavioral Development
Masculinize – promoting male behavior (i.e., mounting)
Defeminize – preventing female behavior (i.e., lordosis)
Perinatal testosterone masculinizes and defeminizes
Neonatal castration of male rats – feminizes and demasculinizes
L1.20

31. Subject: Anne S. The Case of the Woman Who Wasn’t
Anne is chromosomally male, XY
Internalized testes, but no ovaries
Hormone levels are those of a man
Androgenic insensitivity syndrome
Normal male androgen levels, but no response to them
She does respond to estrogens, so she effectively has more estrogens than androgens – leading to the development of female secondary sex characteristics
Subject: Anne S. The Case of the Woman Who Wasn’t
Knowing how normal development occurs, you should be able to understand what could cause abnormal sexual development
Why might a woman not cycle and not have pubic or axillary hair?
What determines whether male or female hormone patterns develop?
What causes the growth of pubic and axillary hair?
Credits
paper clip
©istockphoto.com/Jon Patton
folder
©istockphoto.com/kyoshino
tabletop
©istockphoto.com/Andrew Cribb

32. Subject: Elaine The Case of the Little Girl Who Grew into a Boy
Born with somewhat ambiguous genitals but raised as a girl
Developed male secondary sex characteristics in puberty
Eventually diagnosed with adrenogenital syndrome
Subject: Elaine The Case of the Little Girl Who Grew into a Boy
Andrenogenital syndrome
Andrenogenital syndrome is caused by congenital adrenal hyperplasia
Too little cortisol leads to compensatory excessive release of adrenal androgens in XX females
May masculinize female genitalia and behavior – surgical and hormonal treatments needed at birth.
Often tomboyish; late onset of menstruation
Prior to modern treatments of 1950s, changes in sexual identity at puberty was unpredictable and likely to be traumatic
Credits
paper clip
©istockphoto.com/Jon Patton
folder
©istockphoto.com/kyoshino
tabletop
©istockphoto.com/Andrew Cribb

33. Subject: John/Joan The Case of the Twin Who Lost His Penis
A surgeon’s error led one of a pair of male twins to be raised as a girl
Artificial vagina created
Estrogen administered at puberty
John/Joan never felt or acted like a girl – indicates that the key to one’s gender is in the brain
John/Joan chose to become John later in life, but never recovered from the ordeal
David Reimer (“John”) took his life in May, 2004
Subject: John/Joan The Case of the Twin Who Lost His Penis
Credits
paper clip
©istockphoto.com/Jon Patton
folder
©istockphoto.com/kyoshino
tabletop
©istockphoto.com/Andrew Cribb

34. Male Reproduction-Related Behavior and Testosterone
Effects of orichidectomy (Bremer, 1959)
Reduced sexual interest and behavior
Rate and degree of loss varies
Still have adrenal testosterone
Level of male sexuality is NOT correlated with testosterone levels in healthy men
Increasing male testosterone levels does NOT increase sex drive
L10.17

35. Female Reproduction-Related Behavior and Gonadal Hormones
Rats and guineas pigs – surges of estrogen and progesterone initiate estrus, a period of fertility and receptivity
Women – sexual motivation and behavior not tied to cycle
Sex drive may be under androgenic control
L10.17

36. Human Female Sexuality and Androgens
Testosterone increases the proceptivity of ovariectomized and adrenalectomized female rhesus monkeys
Correlations seen between sexual motivation and testosterone
Testosterone found to rekindle sexual motivation in ovariectomized and adrenalectomized women
L12.21

37. Anabolic Steroid Abuse
Anabolic – growth-promoting
No firm scientific evidence that muscularity and strength are increased
Sex-related side effects
High circulating hormones cause a reduction of natural release (negative feedback loop)
Men – testicular atrophy, sterility, gynecomastia (breast enlargement)
Women – amenorrhea (cessation of menstruation), sterility, hirsutism (excessive growth of body hair)
The smaller an object’s image on the retina, the farther away the object appears.
Wade6.37

38. Neuroprotective Effects of Estradiol
Reduces brain damage if given just before or after inducing cerebral hypoxia
Reduces inflammation, encourages axonal regeneration, promotes synaptogenesis
Increases adult neurogenesis
May account for sex difference in longevity and some diseases
Possible salutary cognitive effects
L7.1

39. Neural Mechanisms of Sexual Behavior
Sexually dimorphic nucleus (SDN)
Medial preoptic area of rat hypothalamus
Larger in males, due to estradiol shortly after birth
Size of male SDN correlated with testosterone levels and aspects of sexual activity
Nuclei in preoptic, suprachiasmatic, and anterior regions of the hypothalamus are larger in men than in women
The human brain
Credits
brain
©istockphoto.com/Stephen Kirklys
neuron
©istockphoto.com/ktsimage
Wood1. 39

40. Medial Preoptic Area of the Hypothalamus
Contains the SDN
Destruction abolishes male sexual behavior of mammalian males and females studied, but does not affect female sexual behaviors in females
Stimulation elicits copulatory behaviors
Evidence favors a motivational role for male sexual behavior
Wood1.
Credit
brain
©istockphoto.com/Stephen Kirklys

41. Ventromedial Nucleus (VMN) of the Hypothalamus
Contains circuits critical for female rat sexual behavior
Lesion eliminates lordosis
Microinjections of estrogen and progesterone induce estrus
Lesions of periaqueductal gray (PAG) or the tracts to it eliminate lordosis
Wood1.
Credit
brain
©istockphoto.com/Stephen Kirklys

42. Sexual Orientation and Sexual Identity
Heterosexual – sexually attracted to members of the opposite sex
Homosexual – sexually attracted to members of the same sex
Bisexual – sexually attracted to members of both sexes
L10.47

43. Sexual Orientation and Genes
48% homosexual concordance rate for monozygotic twins; 16% for dizygotic twins
Limited evidence for a particular gene related to homosexuality
Source: Bouchard & McGue, 1981
Wade3.37

44. Sexual Orientation and Early Hormones
Orchidectomy reduces sexual behavior of males, but does not redirect it
Non-human studies indicate that perinatal hormones can influence sexual “orientation”
Human research is less conclusive
No differences in adult hormone levels
Prenatal exposure to artificial estrogen has weak correlation with homo- or bisexuality in women
Fraternal birth order effect: younger brothers are increasingly more likely to be homosexual
What Triggers the Development of Sexual Attraction?
May be due to adrenal cortex steroids
Adrenal maturation occurs at about the same time (age 10) as sexual interest
Is There a Difference in the Brains of Homosexuals and Heterosexuals?
No reliable difference between the brains of heterosexuals and homosexuals has been discovered
Sexual identity does not always coincide with a person’s anatomical sex
Transsexualism: Person believes that he or she is trapped in the body of the other sex
Wade3.18

45. Independence of Sexual Orientation and Sexual Identity
Sexual attraction, sexual identity, and body type are sometimes unrelated
Points to many possible differences in brain development, organization, and function between individuals
Credits
ruler
©istockphoto.com/Christopher Hudson
woman observing & taking notes
©istockphoto.com/Claudio Arnese

46. Listen: Psychology in the News: Sexuality and Gender
Watch: Adolescence: Identity and Role Development and Sexual Orientation
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47. Acknowledgments Slide Image Description Image Source template
lightning
©istockphoto.com/Soubrette
background texture
©istockphoto.com/Hedda Gjerpen
ch13 image
Affectionate older couple
©istockphoto.com/poco_bw 3
waving
©istockphoto.com/Hongqi Zhang 4
people on treadmills
©istockphoto.com/ShaneKato 5
Figure 13.1
Pinel 8e, p. 328 6
human egg
©istockphoto.com/ChristianAnthony
human sperm
©istockphoto.com/Alexander Kozachok 7
person thinking
©istockphoto.com/akurtz 8
couple hugging
©istockphoto.com/ODonnell Photograf
9, 13, 29, 40, 41
brain
©istockphoto.com/Stephen Kirklys 10
Figure 13.2
Pinel 8e, p. 330 11
calendar month
©istockphoto.com/SwedeAndSour
12, 39
neuron
©istockphoto.com/ktsimage 14
Figure 13.4
Pinel 8e, p. 332
15, 26
book
©istockphoto.com/Carmen Martínez Banús 16
blue sky & clouds, open arms
©istockphoto.com/kertlis 17
Figure 13.5
Pinel 8e, p. 333 18
DNA
©istockphoto.com/HooRoo Graphics
19, 21
pregnant woman
©istockphoto.com/Jim Jurica 19
zygote
©istockphoto.com/Dmitry Knorre
embryo
©istockphoto.com/LM

48. Acknowledgments Slide Image Description Image Source 19, 21 fetus
©istockphoto.com/chrisDownie 20
Figure 13.6
Pinel 8e, p. 334 22
Figure 13.7
Pinel 8e, p. 335 23
restroom doors - gender symbols
©istockphoto.com/k-libre 24
child hugging and kissing another
©istockphoto.com/Nicolesy, Inc. | Nicole S. Young
25, 34, 35
colored gender symbols man woman
©istockphoto.com/Andrew Johnson 27
man pointing at camera
©istockphoto.com/Cat London Photography 28
hand holding rat
©iStockphoto.com/sidsnapper 30
white rat
©iStockphoto.com/Elena Butinova
blue sky & clouds
©istockphoto.com/kertlis
31, 32, 33
paper clip
©istockphoto.com/Jon Patton
folder
©istockphoto.com/kyoshino
tabletop
©istockphoto.com/Andrew Cribb 36
laughing
©istockphoto.com/Stratesigns, Inc. 37
runners at the line
©istockphoto.com/technotr 38
messy files
©istockphoto.com/Jelena Popic 42
couple reading paper together
©istockphoto.com/tomazl 43
twin boys
©istockphoto.com/Thomas Gordon 44
two babies
©istockphoto.com/schwester 45
woman observing & taking notes
©istockphoto.com/Claudio Arnese 46
laptop
©istockphoto.com/CostinT
table and wall
©istockphoto.com/David Clark