Sexual development Flashcards
adult sexual development: females
hips widen
breasts develop
uterus grows & menstration
adult sexual development: males
larynx enlarges
ability to ejaculate
3 main classes of hormone
Amino acid derivatives: synthesised from amino acid molecule
Peptides & proteins: chains of amino acids
Steroid hormones: synthesised from cholesterol (go through the cell membrane)
What is a gonad?
reproductive gland
endocrine
contain sex chromosomes
what hormone class influences sexual development?
steroid hormones
three main types of sex steroid
Androgens (tesosterone) & estrogens (estradiol) & progestin
pituitary glad contains what kind of hormone? Function? Example?
- Tropic hormone (stimulate release of other hormones from other glands)
- gonadotropin
2 parts of the pituitary & function
1) Anterior pituitary – endocrine gland. Controls folicle stimulating hormone & lutenizing hormone
2) posterior pituitary – uses axonal transport. Vasopressin & oxytocin
menstrual cycle - phases & prominent hormone
3 main phases:
1) Follicular phase (estradiol)
2) ovulatory phase (lutenizing hormone)
3) luteal phase (progesterone)
hypothalamic control of the posterior pituitary
- vasop & oxytocin synthsised in nuclei of the hypo
- transported along axons to terminals in PP
- action potential releases the chemicals into bloodstream
hypothalamic control of the anterior pituitary
- neuron FREE
- capillary system instead: hypothalamopituitary portal system (Harris, 1955)
- evidence: Schally, Kastin & Arimura, 1971
3 main ways of hormonal regulation
neural signal regulation: CNS & PNS (autonomic)
regulation via hormones: i.e. tropic hormones
non hormonal chemicals: i.e. glucose/insulin
sexual dimorphisms - what? who found?
male & female structural differences
de vries & sodersten, 2009
Pfeiffer (1936) - what? Results? conclusion?
- semial - work with rats
1) some rats gonadectomised (and some not) & some given transplants (and some not)
Results: gonadectomising rats of either sex caused them to develop female cyclic pattern of release
ALSO transplanting in testes into females = male pattern of gonadotropin release
Conclusion: presence/absence of testicular hormones influences rats dev of pituitary release of gonadotrophin
why was Pfeiffer wrong?
bc the release of gonadotrophin from the anterior pituitary is controlled by the hypothalamus not testicular hormones
though it wasnt totally true, what did Pfieffer reveal?
role of androgens @ birth overriding preporgrammed female cyclic patterns of gonadal tropin relsease
Balthazart & Ball (2006)
- renewed pfeiffer: included the hypothalamus
- aromatisation hypothesis
aromatisation hypothesis – still an older theory
enzymes (aromatase) converts testosterone into estradiol which MASC the brain
modern perspectives on sexual differentiation of the brain: 2 pieces of evidence
MULTIPLE mechanisms is what account for the change in human brains:
1) Jazon & cahill, 2010: sex chromosomes play their own part on gene expression (indep of hormones)
2) Bakker & Baum (2007): we DO need gonadal steroids - estradiol plays an important role
male reproduction related behavioiur & testosterone
- Testosterone LEVELS don’t influence sex drive
- Removing testicles (completely no testosterone) does reduce sexual interest
Female reproduction related behaviour & gonadal hormones
- menstrual cycle
- sexual behaviour is PARTLY controlled by hormones
a) human females copulate outside of fertile window: only species (Ziegler, 2007)
b) androgens seem to motivate sexual motivation in women who have had their ovaries removed
Neural control of sexual behaviour
- association cortex (forgotten)
- hypothalamus
structural diffs between male & female hypothalamus
1) Gorski et al (1978) - in rats: medial preoptic area (inc sexual dimorphic nucleus) = larger in males
2) suprachiasmatic nucleus: “ (Swaab et al. 1994)
3) anterior hypothalamus: “ (Allen et al. 1989)
hypothalamus & male sexual behaviour
Medial preoptic area plays key role (domingues & Hull, 2005)
a) electrical stimulation of MPO elicits copulatory beh in rats ( rodriguez- manzo et al. 2000)
b) lesions affect rats motvation to engage in sexual behaviour (Paredez, 2003)
c) circuits seem to be involved with dopaminagenic pathways (motivation?) Dominguez & Hull 2005
