Sex and the Brain Flashcards
1
Q
How do subcortical structures and the cerebral cortex differentially influence motivated behaviours?
A
- Subcortical structures: urges, drives / motivation to have sex
- Cerebral cortex: Thought / conscious control over behaviours
2
Q
What is the difference between gender and sex?
A
- Sex: Biological state of being male or female determined by chromosomes, hormones, and body anatomy
- Gender: Set of behaviours and attributes a culture associates with men and women
3
Q
What is gender identity? How is gender determined?
A
- Gender identity: perception of our own gender. A complex concept that is not always predicted by biological and behavioural correlates.
- Difficult to determine if behaviours are a consequence of biology, society, or both
4
Q
How many chromosomes do humans have? What are the two different types of chromosomes?
A
- DNA made up of 23 pairs of chromosomes (46 total – 23 from mom, 23 from dad)
- 22 pairs of matching autosomal chromosomes – identical but may have different alleles
- 1 pair of sex chromosomes
- XX = female
- XY = male
- Chromosomes are listed in descending order of size (other than sex chromosomes that are listed last)
5
Q
How many genes are located on the X and Y chromosomes?
A
- X: 800
- Y: 50
6
Q
What is X-inactivation? Give an example of a disorder where this occurs.
A
- If you have two copies of the x chromosomes and something goes wrong with one of them, the functional one can still pick up information lost from the mutated one
- One copy of the x chromosome can be turned down or turned off through transcriptionally inactive structure called heterochromatin
- Heterochromatin is acetylated DNA that can turn off large segments of chromatin so that nothing can get in an transcribe
- Allows cells to pick and choose which information it is getting from the x chromosomes, or to completely turn off the x chromosome
- Example: Fragile X Syndrome. Fragile X Mental Retardation gene mutation – doesn’t appear in females as much because their other x chromosome can mask the genetic abnormality
7
Q
What is the sex determining region of the Y chromosome?
A
- Contains testis determining factor (TDF) protein: Binds to DNA and acts as a transcription factor
- Located on short arm of Y chromosome
- Very important in determining sex: When injected into a fetal XX mouse, causes organism to develop as male
- Regulates genes on other chromosomes
- Causes generation of testes, which then release hormones that release hormones that guide development
8
Q
What is Turner Syndrome?
A
- XO phenotype (absence of one X chromosome)
- Doesn’t occur in males (no cases of YO)
- 1/2500 live births
- most lead to miscarriage, but some make it to term
- some individuals have mild phenotypes: problems reproducing, no menstrual cycle, etc.
9
Q
What is Klinefelter Syndrome?
A
- XXY phenotype
- Individuals are male due to SRY on Y chromosome
- In some cases, there are no phenotypic changes due to extra X chromosome
- Less muscular body, less hair, and increased breast tissue due to lower testosterone production
10
Q
Explain the process of sexual differentiation.
A
- First 6 weeks: Gonadal cells are undifferentiated
- Testes vs. ovaries are determined by hormonal fluctuations in Mullerian duct and Wolffian duct
- Testosterone is produced by any organism that contains the SRY region of the Y chromosome
11
Q
Explain sexual differentiation in males.
A
- Presence of testosterone causes Wolffian duct to develop into the male internal reproductive system
- Testosterone also promotes the production of the gonadal hormone Mullerian inhibiting factor that prevents the Mullerian duct from developing
12
Q
Explain sexual differentiation in females.
A
- Absence of Y chromosome leads to no production of testosterone
- Absence of Mullerian inhibiting factor
- Mullerian duct develops into female internal reproductive system
- Wolffian duct degenerates
13
Q
What are the 3 characteristics of hormones?
A
- release into bloodstream
- travels far distance
- has widespread physiological effects
14
Q
What type of hormones are sex hormones? How do they pass through phospholipid bilayers compared to regular hormones?
A
- steroids: derivative of cholesterol with four carbon rings
- small changes have profound consequences for the effects of sex hormones (all sex hormones have similar structures)
- Steroids readily pass through cell membranes because they are extremely lipid soluble (regular hormones bind extracellularly)
- Act on intracellular receptors within cytoplasm and have direct access to nucleus and gene transcription
- Different tissues have different expression levels of receptors, so different tissues respond to hormones differently (little / no effects in some tissues)
15
Q
What are the names of the sex hormones for men and women?
A
- Men: Androgen
- Women: estrogen
16
Q
What is testosterone?
A
- Androgen steroid hormone
- Released by testes (some from adrenal glands)
- Responsible for masculinizing male bodies
- Females have 1/10 the amount found in males
- Surges of testosterone happen prenatally and at puberty, where they lead to the development of primary and secondary sex characteristics
17
Q
What are estradiol and progesterone?
A
- Principle female hormones
- Secreted by ovaries
- Estradiol = estrogen steroid hormone
- Progesterone = progestin steroid hormone
- Levels increase dramatically at puberty, control the maturation of the female reproductive cycle and the development of breasts
- Hormonal levels follow 28 day cycle
18
Q
How do the hypothalamus and pituitary gland control the release of sex hormones?
A
- Gonadotropin-releasing hormone is secreted by the hypothalamus: releases hormones into pituitary stalk
- GnRH secreting cells are influenced by melatonin (light-dark cycles from eyes). Influence comes from medial preoptic area (where optic tract passes through). Has the ability to change the function of GnRH cells.
- Pituitary controls the release of gonadotropins (luteinizing hormone and follicle-stimulating hormone)
- Anterior pituitary contains gonadotropin secreting cells that make up 10% of cells in the anterior pituitary, and these cells are controlled by hypophysiotropic hormones released by the hypothalamus
19
Q
Explain how LH and FSH influence males.
A
- LH stimulates testes to produce testosterone
- FSH involved in maturation of sperm cells within the testes (testosterone also involved in this)
- Both are required for male fertility
20
Q
Explain how LH and FSH influence females.
A
- Both LH and FSH cause the secretion of estrogen from the ovaries
- In absence of gonadotropins, ovaries are inactive (i.e., childhood)
- Menstrual cycle is determined by cyclic variations in LH and FSH, causing periodic changes to the ovaries
21
Q
Explain how the neural control of sexual behaviour is similar between males and females.
A
- Sexual arousal re-directs blood flow to engorge external genitalia
- External genitalia are loaded with mechanoreceptors connected to sensory nerve endings
- Axons collect in dorsal roots of sacral spinal cord and project to the dorsal horn of the spinal cord – enter dorsal columns and project to brain (same projections that go to the same places)
22
Q
What division of the ANS is responsible for engorgement and erection?
A
- Parasympathetic division
- Stimulation of mechanoreceptors via touch stimulates parasympathetic neurons, which redirects blood flow to body parts with acetylcholine
23
Q
How does the efferent pathway from the cortex influence engorgement and erection?
A
- Higher order brain centres project down onto same parasympathetic postganglionic neurons, which project to sexual genitalia to redirect blood flow
24
Q
What are the 3 things that parasympathetic nerve endings release onto erectile tissue?
A
- Acetylcholine
- Vasoactive Intestinal Polypeptide (smooth muscle relaxation)
- Nitric oxide (smooth muscle relaxation, vasodilation, increased blood flow) – VIAGRA TARGETS NO RECEPTORS
25
Q
What division of the ANS is required to attain an orgasm?
A
- Sympathetic division
- High levels of sensory axon activity in erectile tissues with descending efferent information excite sympathetic neurons
- Sympathetic efferent axons cause a series of muscular contractions in both men and women
- For men: moving sperm through the vas deferent into the urethra
- For women: Vaginal walls thicken, strong muscular contractions
26
Q
What neural structure has been implicated in the emotional components associated with orgasm?
A
- Temporal lobe
27
Q
What is the difference between prairie voles and montane voles? How are they similar?
A
- Prairie voles are monogamous
- Montane voles are polygamous
- Different approaches to sexual partnerships, mating strategies, and parenting
- Similar physically and genetically
28
Q
Explain the chamber experiment with the voles.
A
- 3 chambers: one with partner, one with no other animal, and one with stranger vole
- Present prairie and montane voles with 3 chambers and see which one they prefer
- Montane voles prefer the neutral chamber (being alone)
- Prairie voles prefer chamber with their partner
29
Q
What are the two hormones that may influence mating strategies in voles?
A
- Vasopressin and oxytocin
- More related to groups of neurons they influence rather than the hormones themselves: depends on where the receptors are expressed since there is a different pattern of expression between the two voles
- Vasopressin and oxytocin are protein hormones and bind to extracellular receptors. They show a different pattern of expression between the two voles while all other NT systems are the same
- Expression patterns plastic: Montane voles show similar distribution as prairie voles for the brief period that they raise their offspring
30
Q
Where are the vasopressin and oxytocin receptors located in prairie voles?
A
- Ventral pallidum (limbic loop of basal ganglia) and the nucleus accumbens
- Vasopressin antagonists prevent males from forming a pair-bond relationship with mate in ventral pallidum
- Oxytocin antagonists in females prevents the establishment of a preference with her mate
31
Q
What is the difference in oxytocin and vasopressin receptor expression in monogamous vs. polygamous species?
A
- Monogamous species tend to have oxytocin receptors are expressed in regions associated with reward
- Provides link between social experience and motivation
32
Q
Men with a particular variant in the gene coding for the vasopressin receptor are more likely to:
A
- score the quality of their marriage lower and are more likely to report marital crisis
- Wives of these men also report poorer marriage quality compared to wives of men without genetic variant
