Todays 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
3
Slide 5
Todays 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 4
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Sample test question Sry protein triggers the development of:
a) the testes. b) a Mllerian system. c) the penis. d) ovaries.
5
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Sample test question The aromatization hypothesis states that:
a) Testosterone is directly responsible for masculinizing the brain
b) Male and female brains are not differentiated (i.e. there are no
sex difference in brain development) c) estradiol created in the
brains of developing males from circulating testosterone
masculinizes their brains. d) estradiol created in the brains of
developing females from circulating testosterone feminizes their
brains. 6
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Regulation of gonadal hormones Hypothalamus Gonadotropin
releasing hormone (via veins) Anterior pituitary Gonadotropins
Gonads Estrogens, androgens, progestins Body tissue 8
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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 9
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10
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Male or female? How do we become male or female? What role do
sex hormones play? ? 11
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Think about it A normal genetic female receives injections of
testosterone throughout fetal development. She will be born with:
a) ovaries. b) male internal reproductive ducts. c) undeveloped
female reproductive ducts. d) male external reproductive organs. e)
all of the above 12
Slide 14
Think about it A normal genetic female receives injections of
testosterone throughout fetal development. She will be born with:
a) ovaries. b) male internal reproductive ducts. c) undeveloped
female reproductive ducts. d) male external reproductive organs. e)
all of the above 1:00 13
Slide 15
Think about it A normal genetic female receives injections of
testosterone throughout fetal development. She will be born with:
a) ovaries. b) male internal reproductive ducts. c) undeveloped
female reproductive ducts. d) male external reproductive organs. e)
all of the above :30 14
Slide 16
Activity 2 A normal genetic female receives injections of
testosterone throughout fetal development. She will be born with:
a) ovaries. b) male internal reproductive ducts. c) undeveloped
female reproductive ducts. d) male external reproductive organs. e)
all of the above 4:00 15
Slide 17
Activity 2 A normal genetic female receives injections of
testosterone throughout fetal development. She will be born with:
a) ovaries. b) male internal reproductive ducts. c) undeveloped
female reproductive ducts. d) male external reproductive organs. e)
all of the above 3:00 16
Slide 18
Activity 2 A normal genetic female receives injections of
testosterone throughout fetal development. She will be born with:
a) ovaries. b) male internal reproductive ducts. c) undeveloped
female reproductive ducts. d) male external reproductive organs. e)
all of the above 2:00 17
Slide 19
Activity 2 A normal genetic female receives injections of
testosterone throughout fetal development. She will be born with:
a) ovaries. b) male internal reproductive ducts. c) undeveloped
female reproductive ducts. d) male external reproductive organs. e)
all of the above 1:00 18
Slide 20
Activity 2 A normal genetic female receives injections of
testosterone throughout fetal development. She will be born with:
a) ovaries. b) male internal reproductive ducts. c) undeveloped
female reproductive ducts. d) male external reproductive organs. e)
all of the above :30 19
Slide 21
Activity 2 A normal genetic female receives injections of
testosterone throughout fetal development. She will be born with:
a) ovaries. b) male internal reproductive ducts. c) undeveloped
female reproductive ducts. d) male external reproductive organs. e)
all of the above Times up! 20
Slide 22
Activity 2 - Answer A normal genetic female receives injections
of testosterone throughout fetal development. She will be born
with: a) ovaries. b) male internal reproductive ducts. c)
undeveloped female reproductive ducts. d) male external
reproductive organs. e) all of the above 21
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Activity 2 - Recap Lets walk through typical sexual development
There are three components. Differentiation of the: 1. Gonads
Testes and ovaries 2. Internal reproductive ducts Male includes vas
deferens Female inclues uterus, fallopian tubes 3. External
reproductive organs Male penis, scrotum Female clitoris, labia
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Activity 2 - Recap Gonads 6 weeks after fertilization Both
sexes 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? 23
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Activity 2 - Recap Internal Reproductive Ducts 6 weeks after
fertilization Both sexes Wolffian and Mllerian systems Male Testes
-> androgens -> development of Wolffian Testes ->
Mllerian-inhibiting substance -> degeneration of Mllerian system
Female No testes -> no androgen -> no development of Wolffian
Add testosterone? 24
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Activity 2 - Recap External reproductive organs 2 nd month of
pregnancy Both sexes biopotential precursor Males Testosterone
-> male external genitalia Females No testosterone -> female
external genitalia Add testosterone? 25
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Put it all together. A normal genetic female receives
injections of testosterone throughout fetal development. She is
born with will be born with: a) ovaries. b) male internal
reproductive ducts. c) undeveloped female reproductive ducts. d)
male external reproductive organs. e) all of the above 26
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Puberty Secondary sexual characteristics 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 27
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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 28
Slide 30
Sample test question Sry protein triggers the development of:
a) the testes. b) a Mllerian system. c) the penis. d) ovaries.
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Male vs. female brains 31
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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 32
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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 33
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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) 3:00 34
Slide 36
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) 2:00 35
Slide 37
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) 1:00 36
Slide 38
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) :30 37
Slide 39
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. a) Defend b) Refute Prepare at
least two arguments in support of your decision (i.e. two reasons
why you chose to defend/refute this statement) Times up! 38
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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. a) Defend b) Refute
Presence/absence of testosterone plays a role, but it is far from
the whole story 39
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Activity 3 - Recap Males have higher levels of androgens,
including testosterone (T) Does T act directly on brain to cause
changes? No 40
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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 41
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Activity 3 - Recap BUT.. Most of this research was focused on
the hypothalamus.. of rats! Why? 42
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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
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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
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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 45
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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
46
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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 47
Slide 49
Sample test question The aromatization hypothesis states that:
a) Testosterone is directly responsible for masculinizing the brain
b) Male and female brains are not differentiated (i.e. thereare no
sex difference in brain development) c) estradiol created in the
brains of developing males from circulating testosterone
masculinizes their brains. d) estradiol created in the brains of
developing females from circulating testosterone feminizes their
brains. 48
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Male vs. female? INDIVIDUAL ICA Each person should turn in
their own answer (make sure to put your name on it!) Consider what
youve 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.
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