1. Hormones and Sexuality – Part 1
APSY 214: Unit 3

2. Admin
No office hours this Friday

3. Today’s goals At the end of the today, you should be able to…
Distinguish between the major structures and hormones involved in the regulation of gonadal hormones
Explain the process involved in the regulation of gonadal hormones, starting with the hypothalamus and its hormones
Explain how sexual differentiation occurs for:
Gonads
Internal reproductive ducts
External reproductive organs

4. Today’s goals At the end of the today, you should be able to…
Describe the hormonal changes that occur during puberty and the effect they have on the body
Explain the aromatization hypothesis
Summarize what we understand about sexual differentiation in the mammalian brain, including
Aromatization hypothesis and humans
Key findings in the area

5. Sample test question Sry protein triggers the development of:
the testes.
a Müllerian system.
the penis.
ovaries.

6. Sample test question The aromatization hypothesis states that:
Testosterone is directly responsible for masculinizing the brain
Male and female brains are not differentiated (i.e. there are no sex difference in brain development)
estradiol created in the brains of developing males from circulating testosterone masculinizes their brains.
estradiol created in the brains of developing females from circulating testosterone feminizes their brains.

7. The Neuroendocrine System

8. Regulation of gonadal hormones
Hypothalamus
Gonadotropin releasing hormone (via veins)
Anterior pituitary
Gonadotropins
Gonads
Estrogens, androgens, progestins
Body tissue

9. Goal review You should now be able to…
Distinguish between the major structures and hormones involved in the regulation of gonadal hormones
Explain the process involved in the regulation of gonadal hormones, starting with the hypothalamus and its hormones

10. Sexual differentiation

11. Male or female?
How do we become male or female? What role do sex hormones play? ?

12. Think about it A normal genetic female receives injections of
testosterone throughout fetal development. She will be
born with:
ovaries.
male internal reproductive ducts.
undeveloped female reproductive ducts.
male external reproductive organs.
all of the above

13. 1:00 Think about it A normal genetic female receives injections of
testosterone throughout fetal development. She will be
born with:
ovaries.
male internal reproductive ducts.
undeveloped female reproductive ducts.
male external reproductive organs.
all of the above
1:00

14. :30 Think about it A normal genetic female receives injections of
testosterone throughout fetal development. She will be
born with:
ovaries.
male internal reproductive ducts.
undeveloped female reproductive ducts.
male external reproductive organs.
all of the above
:30

15. 4:00 Activity 2 A normal genetic female receives injections of
testosterone throughout fetal development. She will be
born with:
ovaries.
male internal reproductive ducts.
undeveloped female reproductive ducts.
male external reproductive organs.
all of the above

16. 3:00 Activity 2 A normal genetic female receives injections of
testosterone throughout fetal development. She will be
born with:
ovaries.
male internal reproductive ducts.
undeveloped female reproductive ducts.
male external reproductive organs.
all of the above

17. 2:00 Activity 2 A normal genetic female receives injections of
testosterone throughout fetal development. She will be
born with:
ovaries.
male internal reproductive ducts.
undeveloped female reproductive ducts.
male external reproductive organs.
all of the above

18. 1:00 Activity 2 A normal genetic female receives injections of
testosterone throughout fetal development. She will be
born with:
ovaries.
male internal reproductive ducts.
undeveloped female reproductive ducts.
male external reproductive organs.
all of the above

19. :30 Activity 2 A normal genetic female receives injections of
testosterone throughout fetal development. She will be
born with:
ovaries.
male internal reproductive ducts.
undeveloped female reproductive ducts.
male external reproductive organs.
all of the above

20. Time’s up! Activity 2 A normal genetic female receives injections of
testosterone throughout fetal development. She will be
born with:
ovaries.
male internal reproductive ducts.
undeveloped female reproductive ducts.
male external reproductive organs.
all of the above

21. Activity 2 - Answer A normal genetic female receives injections of
testosterone throughout fetal development. She will be
born with:
ovaries.
male internal reproductive ducts.
undeveloped female reproductive ducts.
male external reproductive organs.
all of the above

22. Activity 2 - Recap Let’s walk through typical sexual development
There are three components. Differentiation of the:
Gonads
Testes and ovaries
Internal reproductive ducts
Male – includes vas deferens
Female – inclues uterus, fallopian tubes
External reproductive organs
Male – penis, scrotum
Female – clitoris, labia

23. Activity 2 - Recap Gonads 6 weeks after fertilization Both sexes Males
Primordial glands
Males
Sry gene (Y chromosome) -> Sry protein -> primordial gonads -> testes
Females
No Sry gene (no Y chromosome) -> no Sry protein -> primoridal gonads -> ovaries
Add testosterone?

24. Activity 2 - Recap Internal Reproductive Ducts
6 weeks after fertilization
Both sexes – Wolffian and Müllerian systems
Male
Testes -> androgens -> development of Wolffian
Testes -> Müllerian-inhibiting substance -> degeneration of Müllerian system
Female
No testes -> no androgen -> no development of Wolffian
Add testosterone?

25. Activity 2 - Recap External reproductive organs 2nd month of pregnancy
Both sexes – biopotential precursor
Males
Testosterone -> male external genitalia
Females
No testosterone -> female external genitalia
Add testosterone?

26. Put it all together…. A normal genetic female receives injections of
testosterone throughout fetal development. She is born
with will be born with:
ovaries.
male internal reproductive ducts.
undeveloped female reproductive ducts.
male external reproductive organs.
all of the above

27. Puberty Secondary sexual characteristics Hormonal changes
Develop during puberty
Distinguish males and females
Not directly involved in reproduction
For example
Facial hair, deep voice, breasts
Hormonal changes
Anterior pituitary -> growth hormone
Anterior pituitary -> gonadotropic and adrenocorticotropic hormones -> maturation of genitals

28. Goal review You should now be able to…
Explain how sexual differentiation occurs
Gonads
Internal reproductive ducts
External reproductive organs
Describe the hormonal changes that occur during puberty and the effect they have on the body

29. Sample test question Sry protein triggers the development of:
the testes.
a Müllerian system.
the penis.
ovaries.

30. Sexual differentiation of the brain

31. Male vs. female brains

32. Think about it
Defend/refute: The differences between the male and
female brains in humans are explained by the presence
or absence of testosterone during development.
1:00

33. :30 Think about it Defend/refute: The differences between the male and
female brains in humans are explained by the presence
or absence of testosterone during development.
:30

34. 3:00 Activity 3 Defend/refute: The differences between the male and
female brains in humans are explained by the presence
or absence of testosterone during development.
Prepare at least two arguments in support of your decision (i.e. two reasons why you chose to defend/refute this statement)

35. 2:00 Activity 3 Defend/refute: The differences between the male and
female brains in humans are explained by the presence
or absence of testosterone during development.
Prepare at least two arguments in support of your decision (i.e. two reasons why you chose to defend/refute this statement)

36. 1:00 Activity 3 Defend/refute: The differences between the male and
female brains in humans are explained by the presence
or absence of testosterone during development.
Prepare at least two arguments in support of your decision (i.e. two reasons why you chose to defend/refute this statement)

37. :30 Activity 3 Defend/refute: The differences between the male and
female brains in humans are explained by the presence
or absence of testosterone during development.
Prepare at least two arguments in support of your decision (i.e. two reasons why you chose to defend/refute this statement)

38. Time’s up!
Activity 3
Defend/refute: The differences between the male and
female brains in humans are explained by the presence
or absence of testosterone during development.
Defend
Refute
Prepare at least two arguments in support of your decision (i.e. two reasons why you chose to defend/refute this statement)

39. Activity 3 - Recap Defend/refute: The differences between the male and
female brains in humans are explained by the presence
or absence of testosterone during development.
Defend
Refute
Presence/absence of testosterone plays a role, but it is far from the whole story

40. Activity 3 - Recap
Males have higher levels of androgens, including testosterone (T)
Does T act directly on brain to cause changes? No

41. Activity 3 - Recap Aromatization hypothesis proposes that:
T is converted into estradiol (aromatization)
Causes masculinization
Evidence for aromatization theory
Early estradiol injections -> masculinize brain
If T present, but aromatization blocked -> no masculinization of brain

42. Activity 3 - Recap BUT….. Why?
Most of this research was focused on the hypothalamus..
…of rats!
Why?

43. Activity 3 - Recap Aromatization hypothesis is not sufficient
Much more complicated
Aromatization only critical in certain brain areas
Substantial variation between species
Variation in different developmental periods within species
Sex chromosomes exhibit unique, independent effects
Estradiol also plays an active role

44. Activity 3 - Recap Take home message
Aromatization hypothesis is not sufficient
Much more complicated
Cause of differentiation varies based on part of brain, species and stage of development
Presence/absence of androgens is not the only important factor

45. Hormones and behavior How do hormones affect behavior?
Most of this research is on rodents
Study reproductive behavior
T in females - masculinizes and defeminizes sexual behavior
No T in males – demasculinizes and feminizes sexual behavior
Much more complicated in humans

46. Masculinization and feminization
Two separate dimensions
NOT opposites
Masculine behavior
Male typical behaviors
Feminine behavior
Female typical behaviors
Can have both at once or neither

47. Goal review You should now be able to…
Explain the aromatization hypothesis
Summarize what we understand about sexual differentiation in the mammalian brain, including
Aromatization hypothesis and humans
Key findings in the area

48. Sample test question The aromatization hypothesis states that:
Testosterone is directly responsible for masculinizing the brain
Male and female brains are not differentiated (i.e. thereare no sex difference in brain development)
estradiol created in the brains of developing males from circulating testosterone masculinizes their brains.
estradiol created in the brains of developing females from circulating testosterone feminizes their brains.

49. In class assignment 4

50. Male vs. female?
INDIVIDUAL ICA – Each person should turn in their own answer (make sure to put your name on it!)
Consider what you’ve learned in your reading (including the three case studies at the end of your reading for today – pp. 340 – 342) and in lecture today
How has this influenced your opinion of what makes us male or female? Do you think “male” and “female” are two distinct separate categories? Why or why not?
There is no correct answer, but make sure to support your opinion with a well-reasoned argument based on class material
Put in team folder or bring to front of class.