Biopsyc - Chapter 13 Hormones and Sex
Terms in this set (111)
What is the 'mamawawa' assumption and why is it wrong?
"men-are-men-and-women-are-women" - meaning that 'maleness' and 'femaleness' are discrete, mutually exclusive, opposite categories.
How do hormones influence sex?
1) by influencing the development from conception to sexual maturity of anatomical, physiological, and behavioural characteristics that distinguish one as female or male (developmental effects)
2) by activating the reproductive-related behaviour of sexually mature adults (activational effects)
name the endocrine glands
are endocrine glands limited to those classically referred to endocrine glands?
no, other organs, stomach, liver, intestines, body fat, also release hormones into general circulation
what are the two types of glands?
exocrine glands - release their chemicals into ducts which carry them to their targets (mostly the surface of the body)
endocrine glands - release their chemicals (hormones) directly into the circulatory system
What are the three classes of hormones?
amino acid derivatives
peptides and proteins
what are amino acid derivatives?
hormones that are synthesized in a few simple steps from an amino acid molecule
where is epinephrine released from and what is it synthesized from?
the adrenal medulla and trysine
What are peptide and protein hormones?
hormones that are synthesized from chains of amino acids
what are steroids?
hormones that are released from cholesterol, a fat molecule
hormones that influence sexual development and activation of adult sexual behaviour are all...?
What is the main difference between between steriod hormones and all other hormones?
most other hormones act by binding to receptors on cell membranes; steroids are fat soluble so they diffuse easily through the cell membrane. this way they can influence gene expression.
Which class of hormone has the longest lasting effects on cellular function?
steroids - because they can influence gene expression
what are the two types of gonadal hormones?
androgens - testosterone
progestings - progesterone
estogens - estradiol
What does progesterone do in women?
prepares the uterus and breasts for pregnancy
unclear in men
what other organ secretes small amounts of sex hormones?
the adrenal gland (the outermost layer of the adrenal cortex)
Where does the posterior pituitary gland develop from?
a small outgrowth of hypothalamic tissue that eventually comes to dangle from hypothalamus
where does the anterior pituitary gland develop from?
from the same tissue that eventually develops into the roof of the mouth, but it pinches off and migrates upwards to assume position beside the posterior pituitary.
which of the two pituitary glands is a better representative of the "master gland"
the anterior pituitary - it releases trophic homrones
What is the main difference between men and women in endocrine function?
women go through a 28ish day hormonal cycle, men do not.
It was originally thought that it was the pituitary glands that caused the difference between males and females cycling. How did they find out that it wasn't?
Harris, in the '50s, transplanted female pituitary glands into males rats and male pituitary glands into female rats and found. They found that the female rats still had cycles and that male rats did not.
What is controlling the posterior pituitary gland?
How is the anterior pituitary gland neurally controlled?
it's not - it receives no neural inpupt
How does the hypothalamus regulate the pituitary gland?
so far, it's unknown, but evidence for the hypothalamopituitary portal system
what are the two mechanisms by which the hypothalamus controls the hypothalamus?
1) one for the posterior pituitary - with vasopressin and oxytocin
2) one for the anterior pituitary - unknown but thought to be with the hypothalamopituitary portal system
what are the two main hormones that work on the posterior pituitary gland? What types of hormones are they? Where are they synthesized and how are they transported?
-vasopressin and oxytocin
-synthesized in the cell bodies of neurons in the paraventricular nuclei and supraoptic nuclei on each side of the hypothalamus
-transported along the axons of these neurons to their terminals in the posterior pituitary and are stored there until the arrival of action potentials
neurons that release hormones into general circulation are called...
what does oxytocin do?
contractions of the uterus during labour and the ejection of milk during suckling
what does vasopressin do?
antidiuretic hormone - facilitates reabsorption of the fluid by the kidneys
What is the hypothalamic portal system?
a network of hypothalamic capillaries that feeds a bundle of portal veins that carries blood down the pituitary stalk into another network of capillaries in the anterior pituitary.
what is a portal vein in a portal system?
a vein that connects one capillary network wih another
what evidence is there for the hypothalamopituitary portal system as the hypothalamic control of anterior pituitary gland?
cutting the portal veins disrupts release of anterior pituitary hormones
hypothalamic hormones that stimulate the release of an anterior pituitary hormone
hypothalamic hormones that inhibit the release of anterior pituitary hormones
gonadotropin-releasing hormones stimulate the release of what from where?
release of follicle-stimulating hormone (FSH) and luteinizing hormones (LH) from anterior pituitary glands
all hypothalamic hormones are what kind of hormones?
how is hormones release regulated?
signals from nervous system
signals for hormones
signals for nonhormonal chemicals in the blood
what endocrine glands have neural control?
all glands except the anterior pituitary
glands that are located in the brain are controlled neurally by what?
glands located outside the CNS are controlled neurally by what?
the autonomic nervous system - both sympathetic and parasympathetic branches
How are the effects of experience on hormone release mediated?
by signals from the nervous system, which may be triggered by signals from the environment (e.g. lengthening of daylight hours)
how is endocrine function mediated by other hormones?
-trophic hormones trigger other endocrine release
-negative feedback from circulating hormones in the blood decrease levels of trophic hormones
how is endocrine function regulated by nonhormonal chemicals?
-circulating chemicals like glucose, calcium, and sodium influence release of hormones (e.g. blood glucose level effects release of insulin)
explain pulsatile hormone release
hormones tend to be released in pulses several times per day in large surges
what is a consequence of pulsatile hormone release?
there are often large minute-to-minute fluctuations in the levels of circulating hormones
what does it mean to have stable levels of hormones? Why?
that levels don't change from day to day, not that they don't change at all. this is because of pulsatile hormone release
describe general gonadal endocrine regulation
neural signals from the brain stimulate the hypothalamus to release GNRH through the hypothalamic portal system which stimulates the anterior pituitary gland to release GNH into general circulation. This stimulates the gonads to release estrogens, androgens, and progestins which target body tissues AND causes feedback effecting subsequent release of these hormones (p. 333)
where does sexual differentiation begin?
at fertilization with the production of one of the two different zygotes (xx or xy)
what do zygotic gonads look like up to 6 weeks of gestation?
regardless of genetic sex, the fetus has the same pair of gonadal structure - primordial gonades which has an outer covering called a cortex which has the potential to develop into ovaries and a internal core called a medulla which has the potential to develop into testes
after 6 weeks of gestation, what triggers sexual differentiation?
the Sry gene on the y chromosome triggeres the synthesis of Sry protein causing the medulla of each primordial gonad to grow and develop into testes
is there a female counterpart to Sry protein?
no - in the absence of Sry protein, the cortical cells of the primordial gonads develop into ovaries
After 6 weeks gestation both males and females have two complete sets of reproductive ducts. What are each called?
the Wolffian system - has the capacity to develop into male reproductive ducts (seminal vesicles, vas deferens)
the Müllerian system - has the capacity to develop into female reproductive ducts (uterus, upper vagina, fallopian tubes)
Around the 3rd month of gestation, more sex differentiation occurs. What happens?
the testes secrete testosterone and mullerian-inhibiting substance.
testosterone stimulates the development of the Wolffian system
mullerian-inhibiting substance causes the mullerian system to degenerate and the testes to descend into the scrotum
How does Mullerian system development go during fetal development?
it occurs in any fetus that is not exposed to testicular hormones during the critical fetal period
removal of testes
Describe development of external genitalia in both males and females.
both develop from the same precursor - bipotential precursor. At the 2nd month of pregnancy the 4 parts begin to develop separately
glans - head of penis or clitoris
urethral folds - fuse in males or enlarge becoming labia minora
lateral bodies - shaft of penis or hood of clitoris
labioscrotal swellings - scrotum or labia majora
what controls development of external genitalia?
presence of absence of testosterone
secondary sex characteristics
those features other than reproductive organs that distinguish sexually mature males and females
How does hormone secretion change at puberty
there is an increase in hormones secreted by the anterior pituitary.
where does growth hormone target?
it acts directly on bones and muscle tissue
what does adrenocorticotropic hormone do?
causes gonads and adrenal cortex to increase their release of gonadal and adrenal hormones which initiates the maturation of genitals and the development of secondary sex characteristics
an androgen that controls growth of pubic hair and axillary hair in females
what did the first studies about sexual dimorphism look into?
Who did these experiments? When?
Describe the experiment and what it found
the factors that controlled the development of steady or cyclic patterns if gonadotropin release in males and females respectively.
Pfeiffer in 1936
some neonatal rats were gonadectomized and some were not, and some received gonad transplants and dome did not.
-Found that gonadectomizing either genetic sex caused them to develop into adults with the female cyclic pattern and transplanting testes into gondoectomized or intact female rats caused them to develop into adults with steady male pattern of gonadotropin release.
-transplantation of ovaries has no effect on the pattern of hormone release
conclusion: female cyclic pattern of gonadotropin release develops inless the preprogrammed female cyclicity is over ridden by testosterone during perinatal development
What did Pfeiffer wrongly conclude in the first studies about sexual dimorphism. Why?
that the presence of absence of testicular hormones in neonatal rats influenced the development of the pituitary. He was not aware that release of gonadotropins from the anterior pituitary are controlled y the hypothalamus.
what is aromatization?
The conversion of testosterone to estradiol by the enzyme aromatase
What is the aromatization hypothesis?
perinatal testosterone does not directly masculinize the brain; the brain is masculinized by estradiol that has been aromatized from
what evidence is there for the aromatization hypothesis?
1) findings demonstrating masculinizing effects on the brain of early estradiol injections
2) findings showing that masculinization of the brain does not occur in response to testosterone that is administered with agents that block aromatization in response to androgens that cannot be aromatized
How do genetic females of species whose brains are masculinized by estradiol keep from being masculinized by their mothers' estradiol, which circulates through the fetal blood supply?
Alpha fetoprotein which deactivates circulating estradiol by binding to it, which is ineffective on testoserone
what body changes are experienced by those who undergo ochidectomy?
reduction of hair on the trunk, extremities, and face; the deposition of fat on the hips and chest; a softening of the skin; a reduction in strength
why did Bremer recommend castration as an effective treatment of last resort for male sex offenders?
Because of the 102 sex offenders in his study who under went castration, only 3 were re-convicted of crimes
Why might some men remain sexually active for months after orchidectormy?
Adrenal androgens might play a role in maintenance of sexual activity
What can testosterone injections NOT do?
it can't eliminate sterility
What two assumptions have come from the fact the testosterone is necessary for male sexual behaviour? Are these correct?
1) That the level of a man's sexuality is a function of the amount of testosterone he has in his body
2)that a man's sex drive can be increased by increasing his testosterone levels
both are incorrect
Experiment that shows that more testosterone ≠ more sex drive
Grunt and Young in 1952
1) they rated level of sexual behaiour in guinea pigs
2) on the basis of that rating they divided the male guinea pigs into three experimental groups: low, medium, and high
4) measurement: sexual behaviour of all guinea pigs fell to negligible levels within a few weeks
5) hormone injections given at the same amount for each guinea pig
6) measurement: although each subject received the same, very large replacement injections of testosterone, the injections simply returned each to its previous level of copulatory activity
what is dihydrotestosterone? What do injections of it do in castrated primates and rodents? What does this show?
a nonaromatizable androgen
it restores the copulatory behaviour of castrated male primates but not in rodents.
conclusion: that the restoration of copulatory behaviour by testosterone occurs by different mechanisms in rodents and primates: is is a direct effect of testosterone in primates, but appears t be produced by estradiol aromatized from testosterone in rodents.
What does ovariectmomy in rats produce?
rapid decline of both proceptive and receptive behaviours
What makes female primates different?
they are motivated to copulate during nonfertile periods
ovariectomy has surprisingly little effect on sexual motivation
is there a correlation between female sex drive and their menstrual cycles?
unsure: some studies find a strong correlation, others do not, the patterns are often different.
what homrone is female sex drive linked to?
androgens - which can be released from adrenals at high enough amounts after ovariectomy to maintain sex drive.
where has support for the theory that androgens control human female sexuality come from?
1) experiments with nonhuman primates, replacement injections of testosterone, but not estradiol, increased the proceptivity of ovariectomized and adrenalectomized in rhesus monkeys
2) in correlational studies of healthy women, various measures of sexual motivation have been shown to correlate with testosterone levels but not with estradiol levels.
3) in clinical studies of women following ovariectomy and adrenalecomy or menopause, replacement injections of testosterone but not of estradiol rekindled the patient's sexual motivations.
Do most women with low sex drive have low levels of circulating testosterone?
steroid hormones that have growth-promoting properties
does testosterone make for a good anabolic steroid?
no because it gets broken down too fast
why were early studies into the effectiveness of anabolic steroid use on improving athletic performance inconclusive?
1) the early experimental studies tended to use dose of steroids smaller than those used by athletes and for shorter periods of time
2) the early studies were often conducted on volunteers who were not involved in intrense training
what negative side effects exist for men who take anabolic steroids?
-negative feedback reduces release of endogenous levels of testosterone which can lead to testicular atrophy and sterility.
-gynocomastia can occur because testosterone is aromatized to estrogens
what negative side effects exist for women who take anabolic steroids?
-hirsutism (growth of body hair)
-growth of the clitoris
-development of masculine body shape
-deepening and coarsening of the voice
Where has evidence about anabolic steroids use causing aggression come from? Why are their claims unconvincing
almost exteriorly from the claims of steroid users
1) because of the general belief that testosterone causes aggression, reports of aggressive behaviour in male steroid users might be a consequence of expectation
2) many individuals who use steroids are likely to have been aggressive before they started treatment
3) aggressive behaviour might be an indirect consequence of increased size and muscularity.
Other than sex-related organization/activational effects, what does estrogen do in the body? Study?
reduces damage associated with stroke and various neurodegenerative disorders. Rats who had had estradiol administered just before cerebral hypoxia had significantly reduced brain damage
What about estradiol might account for its neuroprotective properties?
it has several neurotrophic properties:
encourages axonal regeneration
increases adult neurogenesis
increases survival rate of new neurons
what happens when you inject rats with estradiol?
there is a period in which adult neurogenesis is accelerated followed by a period in which is reduced about 48 hours later.
what might the neuroprotective properties of estrogren account for?
females greater longevity and their lower incidence of several common neuropsychological disorders like parkinson's; and cognitive decline that comes with menopause.
Estrogen therapy has been proposed as a way to decrease cognitive decline in postmenopausal women. What improvements have been made to improve the effectiveness of estradiol therapy?
1) sherwin pointed out that such therapy appears to be effective in both humans and non-humans only if the estradiol treatment is commenced at menopause or shortly thereafter
2) Marriott and Wenk argues that the chronically high dosed that have been administered to postmenopausal women are unnatural and potentially toxic; they recommend instead that estradiol therapy should mimic the natural cycle of estradiol levels in premenopausal women.
why has why has research on the neural mechanisms of sexual behaviour focused almost exclusively on hypothalamic circuits?
1) because of the difficulty of studying the neural mechanisms of complex human behaviours, researchers to focus on the relatively simple, control copulatory behaviours (ejacualation, mounting, lordosis) which tend to be controlled by the hypothalamus
2) because the hypothalamus controls gonadotropin release
3) early studies confirmed that the hypothalamus does play a major role in sexual behavior
what discovery in the 1970s what discovery was made about the se differences in the hypothalamus?
Gorki found that a nucleus of the medial preoptic area of the rat hypothalamus was several times larger in males, called the sexually dimorphic nucleus
How does the sexually dimorphic nucleus change over over time in rats?
At birth it is the same size, a few days later the male sexually dimorphic nucleus grow at a high rate but not the female's.
What triggers sexually dimorphic nucleus growth in males?
estradiol, which is aromatized from testosterone
what is the size of a rat's sexually dimorphic nucleus correlated with?
the rat's testosterone level and aspects of its sexual activity
what do bilateral lesions of the sexually dimorphic nucleus do to male rats?
only slight disruptive effects on male rat sexual behavour
what is the purpose of the sexually dimorphic nucleus?
what sex differences are there in the human hypothalamus?
nuclei in the preopitc, suprachiasmic, and anterior regions of the hypothalamus
Destruction of the medial preoptic area does what?
abolishes sexual behaviour in the males of all mammalian species that have been studies, changes male-like behaviour is females.
i.e. abolish male copulatry behaviour in both sexes
medial preoptic circuits appear to be what?
dopmainergic - dopamine agonist microinjected into the medial preoptic area facilitates male sexual behaivour and dopamine antagonist block it.
why might males with medial preoptic area lesions stop copulating?
maybe they are unable or maybe they are not motivated, evidence pointing to motivation.
one projection from the medial preoptic area goes to where? What does destruction of this tract do? What is activity in the tract correlated with?
lateral tegmental field; it disrupts sexual behaviour in rats; correlated with aspects of copulatory acts.
ventromedial nucleus (VMN)
part of the rat hypothalamus that contains circuits that appear to be critical for female sexual behaviour.
leasions on the ventromedial nucleus produces what?
a total absence of lordosis in female rats and they are likely to attack suitors who become to ardent
injection of progesterone does what?
bring an ovariectomized female rat into estrus as long as it has had an injection of estradiol about 36 hours prior
what does estradiol do to the nervous system?
it primes the nercous system so that the progesterone can exert an effect
what mediates priming by estradiol?
a large increase in progesterone receptors that occurs in the VMN and surrounding area following an estradiol injection
estradiol influences gene expression
what mediates the influence of the VMN on the secual behaiovur of female rats? What does destruction of this mediator do?
a tract that descends to the periaqeductal gray of the tegmentum. destruction eliminates female sexual behaviour as do lesions to the PAG itself.
What genetic evidence is there that sexual orientation has a genetic basis?
male - homosexual males with twins, 52% of monozygotic twins and 22% of dizygotic twins were also homosexual
female - 48% of monotwins and 16% of ditwins