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

Hormones

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

Fig. 30.3A
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

Box 30B
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
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
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
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
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. 30.5
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. 30.6A
INAH (interstitial nuclei of anterior hypothalamus) can be sexually dimorphic

Fig. not in 4th edition
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. 30.8
(this could also be in another chapter)
cortical representation and receptive field of female ventrum changes during lactation

Exam questions from 2005 - 2007 related to this outline
 
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

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