Principles of Neuroscience Lecture 22 Sexuality Flashcards
What does mutation of the SRY gene lead to?
It leads to a female phenotype
No testosterone is produced because we don’t have e testosterone secreting cells
What are the genetic determinants of gender?
Describe how this leads to gender
Where is this gene located?
The SRY (sex determining region Y) It codes for testosterone producing cells in early development
It is located on the Y chromosome, of which males have 1 copy
Which is the “default” gender? How is this changed?
Female is the default gender
The male gender is produced when there is the SRY gene present in the genome (ie a Y chromosome)
Differentiate between the sex hormones
Testosterone: male sex hormone
Estrogen (estradiol) and progesterone: female sex hormones
Describe the sex hormone synthesis pathway
Cholesterol
Progesterone
Testosterone
Estradiol
Why is aromatase important?
It converts testosterone to estradiol
Describe the presence of testosterone throughout the lifetime
It is present during foetal development and then the levels drop at birth
Levels rise again during puberty, and eventually drop off after middle age
Describe the presence of estrogen throughout the lifetime
Levels rise during puberty
Levels fall during menopause
Where do sex hormones act?
In the brain:
- Synapses
- Cell body receptors
What is ER?
Where is it often located?
How does it function?
ER is Estrogen Receptor
It is often located in the cell body
Estrogen binds here, and the receptor-ligand complex alters gene expression
Describe the hypothalamus’ role in sex hormones
It stimulates the pituitary to release LH & FSH
These two hormones bring abo the production of the sex hormones
Where are LH and FSH released from?
The pituitary gland
List a few gender dimorphisms in the brain
- Sexual behaviour
- Sets mediated analgesia
- Cognitive function
- Maternal behaviour
Describe how sexual behaviour is dimorphic in the brain
There is a region in the brain called the Sexually dimorphic nucleus of the Preoptic area
During mating, different neurons fire in this nucleus and at different times depending on the gender of the rat
Describe how stress mediated analgesia is gender dimorphic
The analgesic response to stress is different in males and females
In warm water:
Analgesia depends on endogenous opioids
In males, there is greater sensitivity to the antagonist
In cold water:
Males : analgesia depends on NMDA receptors
Females: this isn’t present
What are the organisational effects of the sex hormones on the brain?
During development, the sex hormones cause differential arrangement and organisation of the brain.
Absence of testosterone will produce a “female” arrangement
What are the activational effects of the sex hormones on the brain?
Give some examples
After development, the circulating levels of the sex hormones brings about different behaviours or activational responses
Premenstrual behaviour
Aggression
Stress mediated analgesia
Regulation of steroid production
What is responsible for the dimorphisms of monogamy and polygamy in different species of voles?
Oxytocin and long vasopressin expression activating the reward centres
Describe how female prairie voles form pair bonds
During copulation, oxytocin is released
These voles have very dense oxytocin receptors
Thus, mating stimulates the reward centres and pair bonds are formed
Describe how male prairie voles form pair bonds
During copulation, long vasopressin is released
This activates the reward centres, and pair bonds are formed
What happens if there is a block in oxytocin in female prairie voles?
The females will not form pair bonds
What happens if long vasopressin is given to a male prairie vole?
He will form a pair bond with a female without copulation taking place
Why don’t Montaine voles form pair bonds?
They don’t have the oxytocin receptors and long vasopressin
