NSCI 201 Chapter Notes - Chapter 30: Sexually Dimorphic Nucleus, Sexual Dimorphism, Estrous Cycle

38 views11 pages

For unlimited access to Textbook Notes, a Class+ subscription is required.

NSCI 201 (23.30)
Sex and Sexuality
7th April 2016
Sex and Sexuality!
!Caveat: Many concepts or experiments in this section, particularly pertaining to humans,
may not be the most accurate—What we know about parental care and nursing is generally fact,
but phenotype and genotype interact in complex ways and cannot be simplified in broad strokes.
Detailed here is simply a series of interesting scientific findings, which by no means define the
intricacies of gender and gender identity. !
!
Sexually dimorphic identity in the tobacco moth!
Strong dimorphism between males and females, particularly in antennae—in these animals,
large parts of sensory systems dedicated to antennae. Male antennae are more feathered, have
different function than female antennae. !
!
There are internal differences as well—in the nervous system, the male has an additional
macroglomerular complex, antennal lobe neurons. !
!
Chromosomal sex and primary sex determination in humans!
!
F: XX; M: XY. Notice that Y chromosome is a
lot shorter— not many Y-linked genes, but
males are at a high risk of X-linked defects.!
!
SRY gene is important in male gonad
specification, as ‘default’ is generally female. !
!
Once specified, testicular tissue secretes
androgens (e.g. testosterones).!
!
Same set of tissues in both sexes,
essentially, bipotential. !
!
Primary sex characteristics: generally, all
genitalia and sexual organs. !
!
Secondary: developing breasts, muscle gain
etc.!
1
Unlock document

This preview shows pages 1-3 of the document.
Unlock all 11 pages and 3 million more documents.

Already have an account? Log in
NSCI 201 (23.30)
Sex and Sexuality
7th April 2016
Gonadal sex steroids and their effects !
All sex steroids are derived from cholesterol, converted to dihydrotestosterone or estradiol
(oestrogen). Oestrogen circulating in the mother’s blood, female-specific effects. Bound/
inactivated by alpha-fetoprotein.!
!
Only hormones active are androgens— testosterone, secreted by testicular tissue, is converted
to one of two forms within a neuron, where alpha-fetoprotein is not active. This means that
testosterone activity is mediated by oestrogen receptors. !
!
Presence of testosterone causes male (i) organisational and (ii) activation effects— (i) tissue
differentiation, setting up development pathways; (ii) response animal will have in response to
hormones and set-up pathways. !
A lot of brain regions are involved— in particular, hypothalamus, preoptic area of the
hypothalamus (secrete hormones from pituitary gland), midbrain regions. A lot of receptors for
sex hormones. !
2
Unlock document

This preview shows pages 1-3 of the document.
Unlock all 11 pages and 3 million more documents.

Already have an account? Log in
NSCI 201 (23.30)
Sex and Sexuality
7th April 2016
Number of spinal motor neurons linked to the perineal muscles is sexually dimorphic!
Male vs female anatomy: differentiation of bipotential tissues based on presence of androgens.
Different musculature, however, is needed for the control of these distinct types of anatomy. !
!
One example: bulbocavernosus muscle, present in early stages in both sexes. Connected to
ventral horn of the spinal cord, can be controlled. Testosterone facilitates growth— in females,
growth is unsupported, muscle atrophies. !
!
There is also a back projection of trophic factors from the muscle, transported back to spinal
cord to keep connection healthy. !
!
In humans, bulbocavernosus muscle persists in females, only less well-developed. Controls
vaginal/ pelvic floor contractions.!
!
!
!
!
!
!
!
!
!
!
!
!
3
Unlock document

This preview shows pages 1-3 of the document.
Unlock all 11 pages and 3 million more documents.

Already have an account? Log in

Get access

Grade+
$10 USD/m
Billed $120 USD annually
Homework Help
Class Notes
Textbook Notes
40 Verified Answers
Study Guides
1 Booster Class
Class+
$8 USD/m
Billed $96 USD annually
Homework Help
Class Notes
Textbook Notes
30 Verified Answers
Study Guides
1 Booster Class