Sex and Neuroendocrinology
Purves et al., Chapter 30, Figure from Chapter 21


"endocrine" - ductless, into blood stream
release - cells with blood vessels

Fig. 30.3A, p. 676
steroids from cholesterol.
They can have permanent perinatal organizing effects
(e.g. neonatal testosterone will make heavier adult female [males eat more])
in addition to sustained or adult effects

John -> Joan -> John (medical pseudonyms), actually Bruce -> Brenda -> David
Electrocautery mishap during circumcision of twin.
Sex change operation.
John Money (Hopkins) - theory that upbringing is as important as chromosomal make-up in gender identity.
Poorly adjusted, demanded to know truth at age 14.
Change back to guy eventually
Money's research seemed interesting at first but was infamous with hindsight

Fig. Box A Chapter 21, p. 456
Hypothalamus (peptides)
(1) Posterior pituitary (peptides
magnocellular neurosecretory cells
oxytocin (milk, delivery)
synthetic to induce labor
vasopressin (ADH), H2O and blood pressure
ADH action on kidney
alcohol, caffein inhibit anti [diuresis] hormone
also low blood pressure -> renin (kidney) ->
angiotensinogen (from liver) - renin -> angiotensin I ->II
affects kidney, blood vessels,
subfornical organ to lateral hypothalamus (for thirst)

Fig. Box A Chapter 21 (again)
(2) Anterior pituitary Master gland
portal system etc.
Hypothalamus parvocellular neurosecretory cells to anterior pituitary
releasing factors
inhibiting factors
Example: CRF-> ACTH->cortisol feeds back to body, hypothalamus, brain
Adrenal cortex - Glucocorticoids, metabolism, inflamation
negative feedback in stress response

Fig. 30.4B, p. 676
Thus (obviously) hormones (estradiol shown here) must bind to brain, and this has been known for a long time (note the reference to McEwen and Pfaff, famous names in this work from the 1970's

Fig. 30.4A, p. 676
recall that steroids affect transcription

Fig. 30.3A [again]
Hormone synthesis
note testosterone can have its affects as 17-beta-estradiol

androgen receptor mutation (androgen insensitivity syndrome [AIS]) -> testicular feminization, children think they are females until there is no menstruation

There are androgens from adrenal, so with Congenital adrenal hyperplasia, CAH, clitoris is large and behavior is "tomboy"

lack of 5-alpha-reductase -> "testes-at-twelve" (at puberty, testes descend, clitoris becomes penis etc when there is enough testosterone to overcome deficit) There is a pedigree in the Dominican Republic.

When I typed "five alpha reductase" or the like into my search engine, I got hits on hair loss, concerning male pattern hair loss (androgenetic alopecia) accelerated by DHT and alleviated by a drug, Propecia

Steroids are involved in photomorphogenesis in plants, and there is a mutant (in Arabidopsis) of a gene with homology to 5-alpha reductase.

Sexual dimorphism

Fig 30.2, p. 671
sex organ development
Sry gene on Y codes for TDF (testicular determining factor)
In female, Wolffian ducts degenerate and Mullerian ducts develop into oviducts, uterus, and cervix (default pathway).
In male, testes make testosterone and MIH (Mullerian inhibiting factor), Mullerian ducts degenerate, Wolffian ducts become epididymus, vas deferens and seminal vesicles (active, not default)
urogenital groove becomes external genitals

A lot of the chapter concerns neural dimorphism, surprisingly not mentioning (much) the original famous example of the part of the bird brain controling song which is male-specific

Fig. 30.5C, p. 677
motor neuron count in spinal cord of Onuf's nucleus controling perineal muscles which function differently in male and female rats
(This is in many ways parallel to the Fig. 23.9 example of spinal motor neuron count being influenced by limb bud ablation or supranumerary limb buds.)

Fig. (no longer in text)
INAH (interstitial nuclei of anterior hypothalamus) can be sexually dimorphic

Fig. (no longer in text)
in work by LeVay, the suggestion is made that homosexuals and heterosexual males differ and that homosexual males resemble more females in hypothalamic area

The book also covers some specific details in differences in cognitive function (a fairly controversial topic and one where it is sometimes difficult to get robust, unconfounded data)

Fig. 30.9, p. 682
(this could also be in another chapter)
cortical representation and receptive field of female ventrum changes during lactation

Exam questions from 2005 - 2012 related to this outline
There are many differences in brain organization of young male vs female people and rats, feeding behavior (body weight) being one example. How AND when are these differences organized?
there is perinatal testosterone in males (there is virtually none in children or prepubertal juveniles)
In the John-Joan-John (Bruce-Brenda-Dave) story, Money's theory about gender identity led to the follow-up treatment from the circumcision. What was Money's proposal?
that gender identity was determined more by environmental factors than by chromosomal or early hormonal factors

In Drosophila, the number of X chromosomes determines gender (XX being female, one X being male). Say something about how this situation is the same or different for humans.
a gene on the Y leads to development of testes which make testosterone and Mullerian inhibiting factor
Where, according to Simon LeVay's data, do homosexual vs heterosexual men have differences in their brains?
interstitial nucleus of the anterior hypothalamus

Testosterone under the skin of a female rat pup would do what to the feeding behavior when she is an adult?

feeding would be more like that of a male, animal would get heavier than a female

Part of the pituitary releases peptides, including ADH (antidiuretic hormone = ADH) that are made in the hypothalamus, and so this part of the pituitary gland is really an extension of the brain rather than a real endocrine gland. Answer either (1) What is this part of the pituitary called? Or (2) What is the other peptide hormone released from this part of the pituitary called?

posterior pituitary (neurohypophisis), oxytocin

What does the story about the sex change operation of a young twin after a mishap in the circumcision operation tell us about gender identity?

it is not based on upbringing as much as previously thought, more biology

Under what circumstances would the adrenal cortex lead to alterations in gender identity or sexual morphology?

congenital adrenal hyperplasia would tend to masculinize female morphology and behavior

How in the world did your professor get from testes at twelve to androgenic alopecia?

testes at 12 is from genetic lack of 5 alpha reductase which creates di hydro testosterone that contributes to the sex-limited trait of baldness

What differences did Simon LeVay find among men in the interstitial nucleus of the anterior hypothalamus?

homosexual vs heterosexual men differ, the homosexual males have a higher cell count and volume, resembling those of women

How is the somatosensory cortex different for non-lactating vs lactating female rats?

there is a larger representation for the ventrum (where the nipples are) if lactation

Say why Money was (or was not) correct about environment dominating over biology in determining gender identity.

the chromosal boy turned to a girl was never adjusted to being a girl, so biology > upbringing in contradiction to Money's idea

What is the product of 5-alpha-reductase?

dihydrotestosterone (DHT)

Name at least one of the substances in early male development contributing to sexual dimorphism.

testicular determining factor, testosterone, Mullerian Inhibiting Factor

Why was the term "receptive fields" applied to describing the difference between lactating and non-lactating rats?

size of receptive field changes with the increased sensory inptu from ventrum (nipples)Where does estradiol bind in the brain?
All over, but strongly in hypothalamus
Human metabolism creates cholesterol. Insect cant do this. Why would cholesterol be an essential nutrient if the body could not biosynthesize it?
Precursor of steroid hormones
Why would hyperplasia of the adrenal cortex lead to masculinization of a female?
Adrenal cortex makes androgens that act like testosterone
The Mullerian ducts degenerate and the Wolffian ducts are supported. Answer either (1) What could lead to this? Or (2) What is the result?
Wolffian ducts become epididymus, seminal vesicles etc, sexual differentiation of male
In his studies of the interstitial nucleus of the anterior hypothalamus (INAH), why did Simon LeVay feel the need to include a control group of heterosexuals who had died of AIDS?
Because most of his male homosexual subjects had died of AIDS
What changes, and in whom, in congenital adrenal hyperplasia?

females may be masculinized (anatomically and behaviorally)

Simon LeVay presented evidence that waht sexually dimorphic area of the brain was altered in homosexual males?

part of hypothalamus

Why would there be a different number of motor neurons in males vs. females in Onuf's nucleus of the spinal cord controlling the perineal muscles?

to mediate male specific behavior

Adult male rats are heavier than females. What is the schedule of testosterone administration to effect a change toward male weight in the female?

one neonatal application

Money's attempt to demonstrate that upbringing predominated over chromosomal makeup in gender identity backfired. How?

boy surgically changed to girl was never adjusted

A figure was shown demonstrating estradiol binding in many parts of the brain, especially the hypothalamus. Where, in the affected brain neurons, would you expect most of this binding to occur?

bound to intracellular receptor protein to control gene trancription

How does the somatosensory projection change during lactation?

larger area and smaller receptive fields for ventrum of dam

Return to Syllabus

Return to Stark home page

This page was last updated 5/23/12