Sex (Lecture 12) Flashcards
sex
biological characteristics that divide organisms into male and female
gender
behavioral characteristics associated with being male or female
gender role
set of behaviors society deems appropriate for people of a given biological sex
gender identity
person’s subjective feeling of being male or female
why has sex evolved?
to reproduce
why sexually reproduce as opposed to on my own (asexually)?
in order to better ft your offspring for a changing environment, different gene provide a greater probability that at lease one gene combination will aid in survival
The Sex Act
Masters and Johnson (1966), identified the 4 stages of sexual response
4 stages of sexual response
- excitement (increased HR, respiration, muscle tone, engorgement of sexual tissue
- plateau (arousal maintained at high level for minutes, preparation for orgasm
- orgasm (rhythmic contractions of genital muscles, intense euphoria)
- resolution (arousal decreases and body regains homeostasis)
male refractory period
unable to become aroused for minutes/hours/days
neural control
may begin in the cerebral cortex (erotic thoughts) but is coordinated (and may begin through stimulation of mechanoreceptors) in spinal cord
info from genitalia or brain activate
parasympathetic NS= engorgement, erection, and lubricating secretions
parasympathetic axons release:
Ach and NO onto erectile tissue (relaxation of smooth muscle= increased blood flow)
increased activity of sensory axons and input from the brain excite:
sympathetic neurons= orgasm (muscle contractions of penis and vaginal walls)
androgens
male hormones, because males have more than females (e.g. testosterone) also produced by adrenals
estrogens and progestins:
female hormones, because females have more than males, (e.g. estradiol, progesterone)
testosterone is important for male ______
male sexual motivation
castration
removal of testes=
- loss of sexual interest and function
- may be maintained IF sexually experienced
- reinstated with T replacement
androgen antagonists
when elected by some criminals:
-80-100% effective in eliminating deviant sexual behavior
hormones important for female ______
female sexual motivation
removal of hormones results in:
(in most species)- females will not copulate unless in “heat”= heightened levels of female sex hormones
(in humans)- will copulate throughout hormonal cycle, but show more initiation of sex during ovulation when estrogen levels are highest
medial pre-optic area of the hypothalamus (mPOA)
involved in male and female sexual behavior
dopamine is important for sexual motivation in:
both sexes and sexual performance in males
DA increases in _____ during sexual stimulation
nucleus accumbens
initially, small amounts of DA during sexual stimulation activate ____ receptors –> activates _______ NS
D1 receptors
parasympathetic
as DA increases, activates ____ receptors –> shifts balance to _____ activation and _____
D2 receptors
sympathetic
orgasm
D2 activation inhibits ____ which accounts for refractory period
erection
the coolidge effect
a quicker return to sexual arousal when a new parter is introduced (this is a dopaminergic effect)
DA increases in NAcc of males when female is presented and then:
DA drops back to baseline as interest wanes following penetrations
introduction of a new female increases _____ again
DA
______ aso contributes to refractory period
serotonin
erection is accompanied by ___ release in hypothalamus –> contributes further to refractory period
5-HT (serotonin)
injection of serotonin reuptake inhibitors into hypothalamus increases:
time until net copulation in male rats and affects ability to ejaculate
SSRIs impair ____ and ____
sexual desire and ability to climax in human users
oxytocin is important for:
smooth muscle contractions (occurring during orgasm)
also important in pair bonding and maternal behaviors
oxytocin is released from the:
posterior pituitary
pheromones
airborne chemicals released by organisms that produce physiological or behavioral effects in another organism of the same species
vomeronasal organ
cluster of receptors in nasal cavity which detect pheromones (sends signals to mPOA and medial amygdala)
PET scans show activation of _________ when subjects “smelled” pheromones
anterior hypothalamus
if fetus has Y chromosome, the SRY gene _____:
SRY gene which codes for protein called TDF (testis-determening factor)
if fetus has NO Y chromosome, the SRY gene __:
is not present
if fetus has Y chromosome, the testes secrete _____:
testosterone and MIH (mullerian inhibiting hormone)
if fetus has NO Y chromosome, the _____:
- mullerian ducts develop into internal genitalia and external genitalia feminized
- wolffian system withers and is absorbed
ovaries do not produce E and P until _____, so feminization is a ____ process in the fetus
puberty
passive
sex hormones have _____ effects and ____ effects
organizational effects
activation effects
organizational effects of hormones
mostly occur prenatally, they affect structure and are lifelong in nature, they are permanent
- development of primary sex organs
- brain organization
activation effect of hormones
can occur at any time individual’s life and may be transient or long
- growth of body hair
- development of brain tissue
- muscle density
fetal testosterone in circulation affects the:
developing brain
steroid hormones can exert their effects in 2 ways:
- bind to enzymes/channels/receptors and alter membrane excitability, sensitivity to NT, or NT release (within seconds)
- enter the cell and go to nucleus to modify gene transcription
testosterone is converted to _____ by _____ and works at estrogen receptors in the brain
converted to estradiol by aromatase
fetal hormones have organizational effects on the brain which may cause structures to become:
sexually dimorphic (different in males and females) leading to differences in behavior
SDN-POA
- 5x larger in male rats
- destruction of SDN reduces male sexual activity
- perinatal aromatase inhibitors block masculinization of structure and function
VMH
- important for female sexual behavior
- active during copulation
- lesion reduce activity
- stimulation facilitates lordosis
preoptic area
four clusters of neurons called the interstital nuclei of the anterior hypothalamus (INAH1-4)
INAH-1
- may be larger in men
- may be human analogue of SDN
INAH-3
- is 2x larger in men
- we don’t know about functional differences
why is it possibly to have a genetic male with a “female brain” and a genetic female with a “male brain”
because hormones are more important than chromosomes for organizing the nervous system
treatment of females early in development with testosterone=
decrease in female sexual behaviors in adulthood
female calves exposed to androgens in utero=
freemartins
Congenital Adrenal Hyperplasia (CAH)
- XX individuals with normal internal genitalia
- enzymatic defect causes over-activity of adrenals early in development
- increased androgens masculinize external genitalia (enlarged clitoris)
- behavior is tomboyish and aggressive
- higher percentage of erotic contact with women
Spatial Task test:
compare males with low T, high T and their performance
-malers with low T during development perform poorly (may be organizational)
-males with higher T perform better (to a point)
(females with higher androgen levels perform better)
possible testosterone link to aggression?
- men kill 30times as often as women
- aggression in males is partly genetic
- testosterone is higher in males rated as more aggressive
- testosterone is increased after winning a sports competition
possible activation effect of estrogen (study if females excel at verbal fluency and writing )
transsexual men taking estrogen supplements score higher on verbal tests than transsexual men not taking estrogen
estrogens increase:
- dendritic spine density in hippocampal neurons
- long term potentiation in hippocampus
dendritic spines=
outcroppings on dendrites that allow neuron to have greater surface area for synapses
rise in estrogen correlated to rise in:
spines
increased spines=
increased excitatory synapses
new synapses shown to have more NMDA receptors
5-alpha reductase deficiency:
-it converts testosterone into DHT during development
-DHT is super potent T that masculinizes external tissue
XY individuals with deficiency may be born with feminized genitalia
