Exam 3 : Neuroscience of Sex Flashcards
Primary sexual characteristics include…
gonads, internal sex organs, external genitalia, influenced by organizational effects of steroid hormones
Secondary sexual characteristics include…
female: enlarged breasts, widened hips
male: beard, deep voice
influenced by activational effects of steroid hormones (puberty)
What are both primary and secondary sexual characteristics caused by?
hormones
process by which individuals develop male-like or female-like bodies and behavior
sex determination
egg carries ___ chromosome from mother
X
___ or ___ chromosome provided by dad
X or Y
on SRY gene
process by which individuals develop either male or female bodies and behaviors
sexual differentiation
Female sexual system
Mullerian system
Male Sexual System
Wolffian system
embryos have early tissues for…
both male and female structures up until the 6th week of prenatal development
embryos have early tissues for…
both male and female structures up until the 6th week of prenatal development
organizational hypothesis of sexual differentiation
one steroid signal - androgens- masculinizes the body, brain, and behavior
Natures impulse is to create…
females
If _____ is not present, the nervous system will organize itself in a feminine fashion
androgens
What does full masculine behavior require?
androgen during development and adulthood
What does sex organ development depend on?
2 hormones released from the testes
what gene stimulates testes formation?
SRY
Testes produce _____ to block Mullerian system
anti-mullerian hormone
- induces withering of female sex organs
Testes produce ______ to stimulate the Wolffian system
androgens
testosterone is converted to ________ which induces development of external male genitalia
dihydrotestosterone (DHT)
Testosterone is converted to ____ via aromatization process
estradiol
- may induce development of masculine brain
- A-fetoprotein in blood binds to estrogen and prevents estrogen from crossing BBB
A-fetoprotein
binds to estrogen and prevents estrogen from crossing BBB
Which system is the default that will develop unless it is inhibited
mullerian system
mullerian system
- no SRY gene
- no anti-mullerian hormone (mullerian develops normal, uterus)
- no testosterone (wolffian ducts do not develop, so no male genitalia)
undeveloped system withers away
secondary sex characteristics appear at
puberty
Puberty is associated with secretion of gonadotropin-releasing hormones (GnRH) from…
the hypothalamus
GnRH induces secretion fom the ____ of ____ and _____
anterior pituitary of FSH (follicle stimulating hormone) and LH (luteinizing hormone)
FSH and LH are secreted in ____ and ____
females: develop ovum
males: stimulate development of sperm, secrete testosterone
secreted by the gonads induces breast development
estradiol
stimulate facial hair, lowered voice, muscle development
androgens
males and females have marked sex differences in appearance
sexual dimorphism
Examples of sexual dimorphism in human brain
PAG: shuts down pain, bigger in females than males (males are wusses)
Sex centers - hypothalamus - males have bigger sex drive
amygdala- emotion, females are more emotional - larger in females
Sex differences: disease prevalence differences
males more likely to have autism, adhd, alcoholism, dyslexia
females: more likely to have anxiety, depression, eating disorders
Male brains are physically larger, but is there a difference in brain region size?
NO
- no size difference in structures in the brain
Is there sexual dimorphism in the human brain?
NO
- social constructs, cultural upbringing
What alters the view of which structures are bigger vs smaller?
idea of sex vs gender
In rats, sexually dimorphic nucleus of the pre-optic area (SDN-POA) of the hypothalamus is larger in ____ than ____
males than females
SDN-POA lesions disrupt…
ovulatory and copulatory behaviors in females and males
SDN-POA in humans
has same cell # and size of cells, but slightly different shape - elongated in women
alters the development of the SDN-POA, resulting in a nucleus permanently larger in males than in females
testicular androgens
androgen insensitivity syndrome
genetic mutation that prevents the formation of androgen receptors
- gonads become testes (normal process)
- defeminization
- lack of masculinzation (the issue!!!)
result of androgen insensitivity syndrome
an XY male with female external genitalia
- have a women’s body but no internal female sex organs
- find out when they do not get period during puberty
- appear baby girl when born even though genetically male
persistent mullerian duct syndrome
failure to produce anti-mullerian hormone and/or absence of receptors for this hormone
results of persistent mullerian duct syndrome
chromosomal makeup? XY
external genitalia: male
defeminization does not occur, but masculinization does
person born with both sets of internal organs (female ones do not wither away)
congenital adrenal hyperplasia (CAH)
adrenal gland secretes abnormal amounts of androgens
- begins prenatally
- causes prenatal masculinization
CAH XY males vs XX females
XY males: typically developmental (just higher androgen levels)
XX females: masculinized external genitalia
- genetically female with normal internal reproductive organs
Intersex appearance: no anti-mullerian hormones, high DHT and testosterone masculinizes external genitalia
Turner’s syndrome
individuals have only one sex chromosome: X
small stature and webbed neck are symptoms
result of turner’s syndrome
essentially develop into females
however, no ovaries since two X chromosomes needed for that and we only have one
In puberty: not same level of hormonal surges, not normal breast development, fat distribution off
Klinefelter syndrome
genetic males have extra X chromosome
- anti-mullerian hormone relatively normal
affects testicular growth, resulting in smaller than normal testicles and lower testosterone production
Klinefelter syndrome results
internal organs - male
more feminized secondary sex - wider hips, less body hair
low sperm counts
how many stages of reproductive behavior?
4
first stage of reproductive behavior?
sexual attraction
may be synchronized with physiological readiness to reproduce and earned associations, such as appearances
sexual attraction
In some species, mated males and females form ______ living together before and long after copulation
lasting pair bonds
when does sexual attraction happen?
after puberty
transmitters involved in sexual attraction
- mesolimbic dopamine
- norepinephrine
motivation to find a mate is governed by…
mesolimbic dopamine system
what is released during attraction?
norepinephrine
mediates sperm production and sexual interest
testosterone
- boys who fail to produce testosterone show little interest in sex until given androgen supplements
just thinking about sex can…
increase testosterone levels in males
- viewing pornography also increases testosterone in males
GnRH antagonists ….
reduce sexual interest and intercourse because no testosterone will be released decreasing sexual drive
testosterone patches
enhance sexual activity in women
what impacts sexual interests in women?
estrogen
- sexual activity initiated by women more during ovulation
women on hormonal birth control vs women with natural cycling
overall women report more interest in their current partner over someone else
- naturally cycling women show a peak in interest in both current partner and other men during ovulation when they are most likely to be fertile
second stage of reproductive behavior
appetitive behaviors
appetitive behaviors
establish, maintain, or promote sexual interaction
what is a proceptive female?
one that wants to have sex
- female rat may approach male or attract by “ear-wiggling”
- production of progesterone increases proceptive behavior and activates receptivity
male rat behaviors in appetitive stage
staying near female, sniffing, singing, nest-building
transmitters involved in appetitive stage
mesolimbic dopamine system and oxytocin release
norepinephrine in arousal (makes you sweat because you cannot believe someone is talking to you)
third stage of reproductive behavior
copulation
copulation
penetrative sexual intercourse ending in ejaculation
- involves one or more intromissions where male penis is inserted in female vagina
- male ejaculates sperm bearing semen into female
transmitters involved in copulation
norepinephrine and serotonin: erectile function (NE inc erection, serotonin dec erection)
dopamine: nigrostriatal dopamine: essential for movements during copulation. mesolimbic dopamine makes you feel good
oxytocin: inc during social bonding - makes you like the person you are having sex with
fourth stage of reproductive behavior
postcopulatory phase
postcopulatory phase
refractory phase - does not exist in women.
coolidge effect
faster resumption of mating behavior with a different partner (random people)
transmitters involved AFTER sex
prolactin: linked to sexual satisfaction in women and men. if sex is good prolactin will inc after ex. levels peak a few min after orgasm
vasopressin: inc in men after orgasm (water balance, social bonding - jealousy)
oxytocin: inc in women after orgasm
where are vasopressin and oxytocin released from
posterior pituitary
