Behavioral Endocrinology- Exam 2
Terms in this set (49)
What, specifically, determines gonad sex in mammals?
sry gene on Y chromosomes
what 2 hormones are required for the normal development of male accessory sex organs in mammals?
mullerian inhibitory hormone =regression of mullerian duct system.
testosterone stimulates development of wolffian duct system.
both are released from embryonic testes.
what effect would 5 alpha- reductase deficiency have on the morphological sex of genetically females?
(males= ambiguous genetalia at birth
male secondary sexual characteristics develop)
you wake up one morning to find that your pet female copperhead head has produced a brood of snakelets.
How is this apparent miracle possible?
(Facultative) parthogenetics- females can produce offspring from unfertilized eggs
Facultative because it can reproduce sexually
obligate- all female species
identify 2 potential costs of asexual reproduction
1)minimal genetic variation: cant "escape" specialized pathogens; as environment changes, cant adapt to live in it
2)no recombination: cant "resuffle" genome to arrive at adaptivr combinations of alleles
Female is the default sex in mammals:
1) explain this statement in the contexts of genetic and hormonal effects on sex determination
2) sterility in XO humans (Turner Syndrome) suggests that normal female development is not entirely defaults. explain.
In the absence of sry, ovaries develop
in the absences of testes the wolffian duct system regresses and the mullerian duct system persists
in the absence of androgens from testes the external genitalia are female
X0 ovaries are non-functional and under-developed which suggest that x chromosome dosages affects gonad sex
What are the 2 main premises of the organizational/ activational hypothesis regarding the role sex steroid hormones in sexually dimorphic behaviors?
the actions of sex steroid hormones on the developing brain permanently alters neural substrates of sexually dimorphic behaviors
At the onset of sexual maturity, the same hormones activate modulate or inhibit this pre-existing neural circuitry, producing predictable patterns of sexually dimorphic behavior
name a sexually dimorphic brain nucleus in either rodents or song birds and identify the sexually dimorphic behavior(s) associated with this nucleus
sexually dimorphic nucleus of the preoptic area: involved in male copulatory behavior
medial preoptic area: involved in male copulatory behavior
high vocal nucleus (HVC), robust nucleus of the archistriatum(RA), area X and others: essential to male song acquisition and production
Hormonal effects on sex differences in human cognition are hard to study.
What is one observation that would support an activating role for sex steroid hormones in male/female differences in a cognitive task?
Sex difference appears at puberty
In oscine birds like zebra finches, only males normally sing. Some results of hormonal manipulations fit well with the expectations of the organizational/activational hypothesis whereas others do not.
Provide an example of each
Consists with O/A effects:
T doesn't stimulate singing in adult female Zfs but estradiol post‐hatching + T as adults does.
Inconsistent with O/A effects:
Eliminating the action of estradiol in male hatchlings doesn't alter adult song
T reinstates singing in adult male Zfs castrated as hatchlings
Name two ways in which prenatal environment can affect sexual differentiation in behavior (without strong effects on morphological sex)
XX female exposure to androgens can masculinize play/ aggression (CAH, rat pups in utero), visuospatial ability (CAH)
Maternal stress during pregnancy demasculinizes play and adult aggression, and feminizes parental behavior in male rats
Sexual preference/orientation: correlation between fraternal birth order and homosexuality in men, possible contribution of androgen exposure to homosexuality in women
What manipulations would you need to carry out to induce female‐specific reproductive behavior (e.g. lordosis) in male rats?
castrate before day 10
inject with estrogen and pregesterone as adult
pair with intact male
What is the function of ovarian follicles and what hormone do they secrete?
Nourish developing oocyte, secrete estrogen
What is the evidence for sex differences in connectivity in the human brain?
Sex differences in degree of lateralization for cognitive functions like map reading and BNE text book reading
Sex differences in morphology of corpus callosum (fiber tract connecting cerebral hemispheres)
Using the time‐honored technique of vaginal lavage, you determine that your female Siberian hamster is in vaginal estrus. You pair her up with a male. She beats the crap out of him.
What was your mistake??
Behavioral estrus = vaginal proestrus,
So actually it's Dr. Pap's fault.
Where is the corpus luteum? When is it there? What does it do?
Ovary: develops from ruptured follicle after ovulation
Prepares uterine lining for blastocyst
implantation if fertilization occurs
Pacing behavior in female rats (approaching males, allowing intromission, withdrawing, etc.) promotes successful pregnancy? How?
Enhances corpus luteum function (essential for preparation of the uterus for implantation) by stimulating pulsed
prolactin secretion from anterior pituitary
Positive regulation and ovulation: Rising levels of _________________ stimulate the surge center in the ____________ to release a surge of ____, which stimulates the ______________ to release a surge of __________, which stimulates the _______ to release more ________________, and ultimately stimulates ovulation.
Positive regulation and ovulation:
Rising levels of [estrogen/esradiol] stimulate the surge center in the [hypothalamus] to release a surge of [GnRH], which stimulates the [anterior pituitary] to release a surge of [LH (and FSH)], which stimulates the [ovaries] to release more [estrogen/estradiol], and ultimately stimulates ovulation.
How is attractivity measured?
Stimulus value of a female for a given male, relative to something else (food, another female, the remote etc.)
What, according to Frank Beach, are the other two components of female sexual behavior? Provide an example of each.
Proceptivity: urine trail in hamsters, bar‐pressing to gain access to male in monkeys, "flirting" behavior in rats
Receptivity:lordosis in rodents
Manipulating hormones in humans is unethical. If you wanted to study behaviors associated with ovulation in healthy women, what would be a logical control group?
Women taking oral contraceptives
In ring doves, receptive behavior and ovulation depend on a behavioral response to male courtship behaviors. What is the behavior and what are its effects in the ovary?
Female's vocal response ("nest coo") stimulates follicular development and estrogen secretion in her own ovary.
Unlike many other primates, human females do not advertise peak fertility or exhibit behavioral estrus.
However, there is considerable evidence that ovulation influences both attractivity and proceptivity in
Provide an example of each.
Heterosexual men rate women photographed during follicular phase as more attractive, more likely to say yes to
date etc. than same women photographed during luteal phase; same
positive effect of ovulation on male rating of women's voices
Attractivity and (maybe) proceptivity:
Lap dancers make more in tips during peak fertility
Women's choice of clothing changes in response to ovulation; follicular phase enhances heterosexual female preference for more "masculine" faces, voices bodies etc.
Which region in the forebrain is essential to lordosis?
If you wanted to eliminate lordosis by knocking out a hormone receptor, which one would you choose?
Estrogen receptor (alpha)
What is the role of hormones in the ascending lordosis circuit?
Estradiol priming required to sensitize flanks. Otherwise not hormone-dependent.
What is the role of the midbrain central gray (MCG) in the descending lordosis circuit?
• Receives signal from ventromedial nucleus of hypothalamus (VMN), transmits signal to brainstem nuclei
• Important for estradiol-‐dependent suppression of visceral negative response to male mating attempts
How could you temporarily eliminate lordosis in an estrus female without any hormonal or neural manipulation, or effect on other behaviors?
Inject local anesthetic into sensitized area on flanks
The action of oxytocin in the ventromedial nucleus (VMN) of the hypothalamus enhances the lordosis response and is estradiol-‐dependent. What, specifically, does estradiol do in this context?
• Estradiol binding to estrogen receptors in VMN
• Promotes expression of oxytocin (OT) receptors
• Promotes temporary extension of OT receptor‐expressing neurons to intercept projections from paraventricular nucleus (PVN) that transport OT to posterior pituitary
XY with non-functional Sry so developes as female
Accessory sex organ for females
Accessory sex organ for males
Testosterone stimulates development of wolffian duct system
Mullerian inhibitory hormone
(MIH) from testes causes regressio. Of mullerian duct
X0 (22.5 sets)
Gonads: incomplete ovary developmen
Need outside estrogen to induce puberty
Kidney functions bad
E.g creeping mole
XXY (23.5 sets)
Female secondary char.
XXY ( 23.5 sets)
Affected cognitive abilities
Atypical sexual differentiation
External genitalia reflect presence of sry
Lack of mullerian inhibitory hormone
In XY mullerian duct system doesn't regress
5 alpha-reductase deficiency
Ambiguous genetalia at birth
Male secondary characteristics
Lacking functional androgen receptors
Man with female parts
Mullerian duct regress
externally female or ambiguous
E.g. moles common in females XX
sterile female twin of a normal male
Organizational/ activational Hypothesis
the actions of sex steroid hormones on the developing brain permanently alter the neural substrates of sexually dimorphic behavior
at the onset of sexual maturity, the same hormones activate, modulate or inhibit this pre-existing neural circuitry, producing predictable patterns of sexually dimorphic behavior
mating posture in receptive female rodents
male-specific behavior in rodents
Hormonal effects on sexual dimorphic experiment
inject testosterone in developing rodent
perform gonadectomy on male and female progeny before day 10
inject T-exposted female with estrogen and progesterone
paired with unmanipulated male
no signs of lordosis
inject female with testosterone
pair with unmanipulated female
sexual dimorphism in the brain: how might hormones organize the neural substrates of behavior?
Effect dendritic branching/ axonal projection: Connective differences
Effects on neural survival: volumetric diff.
Effects on distribution of neurohormone receptors and neurotransmitters: molecular differences
in Preoptic area (hypothalamus): important to male copulatory behavior in rats and other rodents
singing behavior is sexually dimorphic