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Integrative Neuroscience > Sex and the Brain > Flashcards

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
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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
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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
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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)
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5
Q

How many genes are located on the X and Y chromosomes?

A
  • X: 800

- Y: 50

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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
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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
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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.
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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
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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
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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
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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
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13
Q

What are the 3 characteristics of hormones?

A
  1. release into bloodstream
  2. travels far distance
  3. has widespread physiological effects
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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)
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15
Q

What are the names of the sex hormones for men and women?

A
  • Men: Androgen

- Women: estrogen

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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
  1. Acetylcholine
  2. Vasoactive Intestinal Polypeptide (smooth muscle relaxation)
  3. 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

Integrative Neuroscience (9 decks)

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