Sex Flashcards
How do hormones act?
Hormones act in a gradual fashion
Hormones often have pulsatile secretion – in bursts
Some hormones are controlled by circadian clocks
Tropic hormones
pituitary hormones that affect other endocrine glands
Releasing hormones
hormones released from hypothalamus control pituitary’s release of tropic hormones
secreted into local blood vessels
Vasopressin
raises blood pressure and inhibits urine formation
Oxytocin
Maternal behaviors
Oxytocin rises in women in affectionate relationships, and in those in distressed relationships
Hypothalamic neurons
synthesize releasing hormones
Thyroid hormones
contain iodine and depend on its supply
cretinism
Early thyroid deficiency results in cretinism with mental retardation
goiter
a swelling of the thyroid gland from iodine deficiency
Endocrine pathology
mimics psychiatric disorders
Cushing’s disease
results from long-term excess glucocorticoids, with fatigue and depression
Sexual Orientation
3.5% of American adults identify as lesbian, gay or bisexual, 0.3% are transgender - about 12 million Americans total
Homosexuality is 2-7 times higher among siblings of homosexuals than in population
INAH3
(third interstitial nucleus of the anterior hypothalamus) is female-sized (smaller) in gay men
Suprachiasmatic nucleus (SCN)
larger in gay men than in heterosexual men and contains more vasopressin-secreting cells
Anterior commissure (AC)
is larger in gay men and heterosexual women than in heterosexual men
Gay men’s verbal and spatial performance is more similar to women’s than to heterosexual men’s
Why do we have sex?
Reproduction (more of us)
DNA shuffling (but not exactly us)
It’s fun (uniquely human?)
estrus
If a female is sexually receptive she is in estrus (non-human)
Androgen
a male sex hormone, such as testosterone
sexual response curve
In both men and women:
1) Excitement phase (arousal)
2) In plateau arousal levels off
3) Orgasm
4) Resolution, as arousal falls and body returns to normal
primary area of activation in brain during male orgasm
ventral tegmental area
primary area of activation/inhibition in brain during female orgasm
Activation of the deep cerebellar nuclei
Inhibition of orbitofrontal cortex
Medial amygdala
Involved in sex, smell, aggression, and emotions
Sexually dimorphic nucleus
male
Located in MPOA (INH3) (medial preoptic area) 2-3x larger in men Male sexual activity related to its size Size depends on prenatal exposure to testosterone
Ventromedial hypothalamus
female
Receptivity to male advances
Dopamine (DA) (+)
DA activity in MPOA motivates sex behavior in both sexes, esp. in men
Drugs that increase DA increase sexual activity in humans
Increasing levels of DA produce erection in males, then ejaculation
Serotonin (5HT) (-)
Injecting SSRI into LH increases time before male rats attempt to copulate again
Both men and women complain SSRIs impair their sexual ability
SRY gene (sex-determining region on Y chromosome)
responsible for development of testes - Without an SRY gene, an ovary forms
Organizing effects
mostly occur prenatally or shortly after birth
They affect structure and are lifelong
Activating effects
occur at any time in life
Come/go with hormone fluctuations or are long lasting, but are reversible
Hormone surges at puberty
trigger both organizing and activating effects:
Organizing effects:
Maturation of genitalia
Growth spurts
Activating effects at puberty:
Breast growth in girls and egg release during menstrual cycle
Sperm production, muscle development, hair growth in boys
and a dramatic increase in sexual interest
masculinization
appears to be direct effect of testosterone on the developing brain:
Two testosterone surges in human pregnancy
weeks 12 and 18
weeks 34 to 40
estradiol
masculinizes the nonprimate brain
Male:
Testosterone secreted into the blood reaches brain
Testosterone converted there to estradiol and dihydrotestosterone
Estradiol masculinizes the brain
Female:
A-fetoprotein in blood binds to estradiol
Prevents estradiol from entering brain
Protects female brains from being masculinized by estradiol
male brains vs. female brains
Males have greater asymmetry than females
Right hemisphere thicker in males than females
male/female differences
Most girls have greater verbal ability than most boys
Most boys excel in visual-spatial ability
Most boys are more physically aggressive than girls
There are more boys who are great at math than girls; but overall ability is the same
High estrogen level
associated with
depressed spatial ability
enhanced speech and manual skill tasks
Testosterone during the 2nd trimester
increases cerebral asymmetry via accelerated growth of the right hemisphere
gender division
Gender is a continuum, not a dichotomy
Gender-Related Behavioral and Cognitive Disorders
Men are more susceptible to autism, Tourette’s syndrome, dyslexia, ADHD
Women are more likely to suffer from depression, anxiety, autoimmune diseases
Testosterone suppresses inflammation; low testosterone levels predict premature death from heart disease
brain activity during spatial rotations in females
Women rely more on frontal areas to perform spatial rotations
female corpus callosum
women have larger corpus callosum
size of corpus callosum correlates with cognitive skills in women
