Chapter 12: Sex and Behavior Flashcards
sexual behavior
neural circuitry of the brain that regulates reproductive behavior
what guides reproductive behavior in many species?
pheromones
reproductive behavior stages
- sexual attraction
- appetite behavior
- copulation
- postcopulatory behavior
sexual attraction
brings males and females together
sexual attraction can be synchronized with…
- physiological readiness to reproduce, indicated by odors reflecting estrogen levels in females
- learned associations, such as appearances
appetite behavior
establish, maintain, or promote sexual interaction
appetite behavior is _____
proceptive
- behavioral cue that a female displays to initiate or maintain sexual interaction with a male
copulation
one or more intromissions in which a male penis is inserted with the female vagina
what occurs after copulation?
male ejaculates sperm bearing semen into female
what happens after first copulatory phase?
refractory phase: cannot have another orgasm
- lengthens with age
coolidge effect
faster resumption of mating behavior, with a different partner
what is estrus? and who shows it?
females who are willing to copulate are in estrus
estrus: sexually receptive
postcopulatory behavior
the activity that occurs immediately after copulation between two animals
copulatory lock
penis swells temporarily and cannot be withdrawn from female
what does postcopulatory behaviors include?
parental behaviors to nurture offspring
- varies among species
internal fertilization
fusion of gametes to produce a zygote inside the body
gametes: sperm in male and ova in females
external fertilization
occurs outside body
- fishes and frogs release gametes into water
ovulation
releasing eggs
estrus
female displays proceptive behavior and adopts a posture called lordosis
lordosis
allows intromission
pair bonds
strong social relationship formed between two animals of the same species who live together before and after copulation
sex steroids
important for mating behaviors
castrated
testosterone is no longer produced, causes losing interest in mating
activational effect
hormones briefly activate behavior
- can restore behavior
which estrogens are important for female proceptive behavior in rats?
estrogens produced in the beginning of the ovulatory cycle
progesterone
more increases in proceptive behavior and make females receptive
what do females without ovaries respond to?
combination of estrogen and progesterone treatments to make her proceptive and receptive
what brain structure is crucial for lordosis response through steroid actions?
ventromedial hypothalamus
what does the VMH do in the ovulatory cycle?
sends axons to periaqueductal gray in the midbrain»_space;> medullary reticular formation» spinal cord»_space; reticulospinal tract
what does estrogen cause?
increase in dendritic trees of neurons in VMH and production of progesterone receptors, which contributes to lordosis through protein production
what brain structure coordinates male copulatory behavior?
medial preoptic area (mPOA)
what does the mPOA do in the reproductive cycle?
sends axons to ventral midbrain»_space;> basal ganglia»_space; brainstem nuclei»_space;> spinal cord
what does the paragigantocellular nucleus do for the male reproductive behavior?
inhibits erection response, then the mPOA signals counteract the inhibition
vomeronasal organ
detects pheromones that activate male arousal
where does the VMO send axons?
medial amygdala and turn to the mPOA
4 phases of response in human sexual behavior
- excitement
- plateau
- orgasm
- resolution
excitement
phallus becomes erect and there in increased blood flow to the vagina, leading to lubrication of fluids
orgasm
activation of variety of brain structures
what brain structures activate during an orgasm?
amygdala, cingulate cortex, nucleus accumbens, hippocampus
what are the activation of hypothalamic areas responsible for?
release of oxytocin, which occurs after an orgasm
sexual response in women
more selective in choosing someone for potential romance
sexual response in males
have absolute refractory phase following an orgasm
have stronger sex drives
sexual response in paralyzed women
can still have orgasms because the vagal nerve detects stimulation which leads to same activation of brain structures
example of pheromones affecting human reproductive behavior
menstrual cycles of women living together can synchronize
Major Histocompability Complex
group of immune-related genes with many alleles
women’s preferences in MHC
prefer the smell of men with MHCs not too similar or dissimilar to their own
precocial
animals that are born in a relatively developed state and are able to survive with little maternal care
what are precocial animals born with?
well developed sensory and motor systems
example: horses
altricial
animals born in an undeveloped state and depend on maternal care
example: humans
who is involved in caring for their young in altricial animals?
males and females
rat mother behaviors
- nest building
- crouching over pups
- retrieving pups
- nursing
what prepares rat mothers for maternal behavior?
during pregnancy, exposure to hormones prepares her brain to display these behaviors immediately after giving birth
parabiotic
surgical preparation that joins two animals to share a single blood supply
example of parabiotic
nonpregnant female exposed to circulating hormones of a pregnant rat with display the same maternal behaviors
what brain structure is involved in maternal behaviors?
mPOA and periaqaeductal gray
sexual differentiation
physical process by which individuals develop male or females’ body and behavior
sexual determination
genetic development even that decides if a fetus will be male or female
when does sexual determination begin?
in utero and continues into adulthood
what is the sex determining cell that carries either X or Y?
sperm
what always contains an X chromosome?
ovum
genes for male and female
XX = female
XY = male
indifferent gonads
undifferentiated gonads of the early vertebrate fetus, which develop into testes or ovaries in the first month
SRY gene
sex determining region on the Y chromosome, responsible for tests
- leads to domino effect in development of sex
what happens with an SRY gene on the Y chromosome?
an ovary forms
which gonad produces several hormones and which produces little hormone?
testes produce several hormone
ovaries produce little hormones
what directs sexual differentiation?
hormones secreted by gonads, mainly testes
exposure of testicular hormones
when exposed to testicular hormones, many tissues of the body begin developing masculine characters
- if cells are not exposed to testicular hormones, they develop feminine characters
what does differential exposure lead to?
differential exposure to sex steroids leads to differences in gene expression throughout body
what type of tissues do embryos have?
embryos have early tissues for both male and female structures
wolffian duct
duct system in the embryo that develops into male structures and mullerian duct shrinks
male structures
epididymis, vas deferens, seminal vesicles
mullerian ducts
duct system in the embryo that develops into female structures and part of the wolffian duct remains
female structures
fallopian tubes, uterus, vagina
what hormones from testes make the system masculine?
testosterone: promotes development of wolffian system
anti-mullerian hormone (AMH): induces reversal of the mullerian system
5a-reductase
enzyme that converts testosterone into more powerful dihydrotestosterone
- found in genital skin
dihydrotestosterone
potent androgen necessary to form genitalia
what happens without local DHT production?
genitalia becomes partially masculinized
what happens without any testosterone?
genitals become labia and clitoris
turner’s syndrome
person only has one sex chromosome, a single X
what does a person with turners syndrome develop as?
female, without the SRY gene
has recognizable ovaries but underdeveloped and no masculinizing effects take place
congenital adrenal hyperplasia
result of female exposure to androgens before birth
how does CAH occur?
adrenal glads fail to produce corticosteroids and produce androgens»_space;> leads to intersex appearance
cloacal extrophy
genetic males born with testes but no penises
androgen insensitivity syndrome (AIS)
occurs in XY people whose androgen receptors do not produce testosterone
what occurs in people with AIS?
testes produce testosterone and AMH but no androgen receptors prevents the development of male features
what external genitalia do those with AIS have?
female genitals and develop as women
organizational effect
permanent alteration of nervous system, causing permanent change in behavior, resulting from action of a steroid hormone early in development
steroids
have organizational effect only when present during a sensitive period in early development
sensitive period
period during development in which an organism can be permanently altered by particular experience or treatment
sensitive period times
neonatal period and puberty
organizational hypothesis
explains sexual differentiation
aromatization hypothesis
says that testosterone enters the brain and is converted into estrogens
aromatization
enzyme aromatase converts testosterone to estradiol
A-fetoprotein
binds estrogen keeping it in the blood stream and prevents it from entering brain
- prevents aromatization and masculinization
- does not bind testosterone
sexual dimorphism
refers to sex differences in behavior or in structure
preoptic area
nucleus in POA is larger in male rats than female rats
what makes the POA in male rats larger?
testicular androgens
what does genital licking do for rats?
for males: greater licking masculinizes the developing system and important for SNB cell survival
for females: greater licking creates more attentive mothers in the future
what happens during puberty for males?
testosterone leads to development of small penis and body becomes masculinized
- become sexually interested in women and start behaving as men
guevedoces
boys who are raised as girls, but grow penis and then behave as men in adulthood
two classes of influence on sexual orientation
society’s instruction on how should behave when grown up
biological factor
biological factor
varying levels of fetal androgens directs whether developing brains are attracted to females or males in adulthood
what is the conclusion on sexual orientation?
sexual orientation in both sexes is determined early in life
