Sex And The Brain Flashcards
Define sex
Biological state of being male or female, and is determined by chromosomes, hormones and body anatomy.
Define gender
Set of behaviours and attributes a culture associated with men and women.
Define gender identity
Our perception of our own gender
How many genes are in the X and Y chromosome?
X - 800 genes
Y - 50 genes
What does the sex-determining region of the Y chromosome (SRY) code for?
Protein called testis-determining factor (TDF)
Where is the SRY gene located?
Short arm of Y chromosome
Define turner syndrome
Partial or complete absence of one X chromosome in a female (XO genotype)
What are the characteristics of turner syndrome?
Short stature
Receding jaw
Webbed neck
Visuospatial and memory difficulties
Define Klinefelter syndrome
Extra X chromosome
How do the gonads determine sex?
During first 6 weeks of pregnancy, no changes but contains the Wolffian duct and Müllerian duct
Male - Wolffian duct develops into male internal reproductive system due to release of testosterone. Mullerian-inhibiting factor also produced to inhibit female organs.
Female - Müllerian duct develops and Wolffian degenerates
Name male hormones
Androgens
Name female hormones
Estrogens
What is estradiol synthesised from?
Testosterone using aromatase
What is the primarily responsibility of the testes?
Release of androgens
What is the principal female hormone?
Estradiol and progesterone - secreted by ovaries
Name the two hormones secreted by the pituitary gland for normal sexual development?
Luteinizing hormone (LH)
Follicle-stimulating hormone (FSH)
Describe role of gonadotropin-releasing hormone (GnRH)
Causes release of LH and FSH
What does gonadotrophins stimulate in males?
LH stimulates the testes to produce testosterone
FSH matures sperm cells
What does gonadotrophins stimulate in females?
LH and FSH cause the secretion of estrogen from the ovaries - menstrual cycle
State the sexual response cycle
Arousal
Plateau
Orgasm
Resolution
What is the pathway from genitals to brain
Axons from mechanoreceptors in the pen is and clitoris collect in the dorsal roots of the sacral spinal cord. They then send branches into the dorsal horns of the cord and into the dorsal columns through which they project toward the brain
Engorgement and erection are primarily controlled by what?
Axons in the parasympathetic division of the ANS
What does parasympathetic nerve endings release during sexual arousal?
ACh, vasoactive intestinal, polypeptide (VIP) and nitric oxide (NO)
Cause relaxation of arteries and the spongy substance of the clitoris and penis
What completes the sexual response cycle?
Sympathetic division of the ANS
What does the sympathetic efferent axon trigger in men and women?
Men - emission
Women - orgasm
Define polygyny
Male mates with many females but the female mates with only one male for one or multiple mating seasons
Define polyandry
One female mates with many males but the male mates with one female
Define monogamy
Male and female forms tightly bound relationship that includes exclusive mating
What is the difference between prairie voles and montane voles?
Prairie voles - monogamy
Montane voles - only female looks after children
What effects does vasopressin have on mating?
High = forms relationship
Low/ blocked = no attachment
How does oxytocin and vasopressin assist in parenting habits
High levels = more bonding
What brain areas are activated when people see a picture of partner or children
Anterior cingulate cortex, caudate nucleus, striatum
Define sexual dimorphism
A sex related difference in structure or behaviour
What is the sexually dimorphic nucleus?
A nucleus ear the third ventricle which is 5-8 times larger in males than females
What neurons in the pre optic area are different in men and women?
Interstitial nuclei of the anterior hypothalamus (INAH)
Larger in men, particularly the INAH 3
What do women tend to perform better on then men?
Verbal tasks
Naming objects of same colour
Listing words beginning with the same letter
Verbal memory
What do men outperform women in?
Map reading
Maze learning
Mathematical reasoning
Mental rotation of objects
How do steroids influence neurons?
- Act quickly in altering membrane excitability, sensitivity to neurotransmitters, or neurotransmitter release.
- Diffuse across the outer membrane and bind to specific types of of steroids receptors in the cytoplasm and nucleus
Define organisational effect
The ability of a hormone to influence the prenatal development of sexual organs and the brain
Define activational effect
The ability of a hormone to activate reproductive processes or behaviours in a mature organism.
What hormone causes the changes in gene expression responsible for masculinisation?
Estrogen - testosterone levels lead to increase in estrogen level s
What is a-fetoprotein?
A protein found in high concentrations in feral blood, binds estrogen and protects the female foetus from masculinisation.
What happens to a mouse that lacks a-fetoprotein?
Sterile and do not exhibit normal sexual behaviours
What levels of a-fetoprotein in found in Down syndrome
Unusually low levels
What are prostaglandins and what is there role?
Compounds derived from arachidonic acid - requires cyclooxygenase (COX) for synthesis
Produced after tissue damage and involved in inducing pain and fever
What did COX inhibits do to rodents?
Males - Reduced copulatory behaviour as rats
Females - exhibited male like copulatory behaviour. Increased masculinisation
What is lordosis
Fail to elicit they typical female mating posture
What are androgen-insensitive men?
Defecting androgens gene on X chromosome
Look and behave like female. Undescended testes
What is congenital adrenal hyperplasia?
Secrete large amounts of androgens - external genitals are intermediate between a normal clitoris and penis
What is the role of genes?
Direct the development of the gonads, and the hormonal secretions of the gonads control sexual differentiation.
What is the purpose of the fru gene in flies?
Presence - develops courtship behaviour in males
Absence - normal female behaviour
What happens when leptin levels rise during pregnancy?
Appetite and food consumption increase
Does fatherhood change the brain in marmosets?
Yes
Fathers - higher density of dendritic spines on pyramidal cells and more vassopressin receptors
How does estradiol affect neurons.
Modulates flow of potassium ions, estradiol depolarises some neurons and cause them to fire more action potentials
Increases dendritic spines
How does estradiol affect maze runners?
Enhances performance hours later
How does INAH potentially affect sexual orientation?
INAH 3 is half the size in gay men when compared to straight men
