Hormones and sex Flashcards
(17 cards)
Hormones and the brain
A hormone is a signalling molecule that is transported in the blood supply via the vascular system
essential for the regulation f development, physiology and behaviour
produced by many organ of the body (the endocrine system), with receptors similarly located in many places
Under master control of the hypothalamus
Set point
Hormones act to maintain a desired set point in terms of behaviour or physiology
Hormones vs neurotransmitters
Hormones:
Act slower
Act over longer distances
Can travel anywhere where there is blood supply
Have a long duration of action
Have more diffuse actions- more widespread
Compared to neurotransmitters
Hypothalamus
Receives contextual and sensory information
Can see current state of body and current context, can make adjustments to physiology and behaviour via hormones
Anterior pituitary
Neurosecretory cell in the hypothalamus releases hormones into the blood vessels that go into the pituitary gland- causing a release of more hormones
Posterior pituitary
Neurosecretory cell goes straight from the hypothalamus and released into the blood supply
Chromosomal sex
Most humans have 22 pairs of autosomes and one pair of allosomes
Autosomes- like one another
Allosomes- not like one another
Allosome pair (XX or XY)- sex chromosome
Fixed
Phenotypic sex
Refers to internal and external genitalia
Gender
An individuals subjective perception of their sex
Variations in chromosome
Turner syndrome (XO) missing X chromosome in females
Tend to be shorter in height and have impaired ovary function - ovaries produce oestrogen and progesterone- reduced levels of these lead to underdevelopment of sex characteristics
Can be treated with oestrogen and progesterone
Klinefelter’s syndrome
Extra X chromosome (XXY) affects males
Boys with Klinefelter’s syndrome tend to be taller ad have impaired testicular function
The testicles produce testosterone- reduced levels of this lead to under development of sex characteristics
XYY syndrome
Extra Y chromosome in males
Usually taller
symptoms are usually mild therefore people are underdiagnosed
Importance of X chromosome
X chromosome contains 15000 genes, Y contains around 80
SRY gene
The SRY gene is important for the diversion towards male biological development in utero- when the foetus is around 6-8 weeks old
If you chemically block SRY action you get a genetic male (XY) but with ovaries.
If you inject SRY where there should be you get a genetic female (XX) with testes
Chromosomal testing to determine male or female
Olympics tested the presence of SRY gene in order to determine whether people were male or female
It was later shown that 8 self-declared female athletes who had a SRY gene had an insensitivity to androgen (testosterone is a form)
They were therefore phenotypically female
This was replaced with hormone based testing
Hypothalamus and secondary sex characteristic production
The sex hormones (testosterone/oestrogen/progesterone inhibit anterior pituitary and hypothalamus function
After time- the Hyp and AP because less sensitive to this inhibition from the hormones and more sex hormones are released
Activity is pulsatile- releasing GnRH into the AP, which leads to LH and FSH release
Pulsating rate increases towards puberty, leading to increase LH and FSH signalling, leading to sex hormone release
Sex differences in the brain
Make and female brains are different sizes, on average male brains weigh about 10% more than female brains
Bad science:
Motivations-
Bad design-
Questionable comparisons- some animals have big differences between male and females- shouldn’t compare these to humans
Publication bias- If you find a difference you are more likely to be published- but you could be wrong
Why do we care?
Many conditions have different level of incidence in men and women- are these because of differences in the brain.
