Brain & Behaviour Lectures 1-4

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  • Created by: Laelae
  • Created on: 31-01-18 20:37
Why have sex?
For genetic variety of organisms within a species; this aids survival
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What are the 3 fundamental steps of sexual reproduction?
Gametogenesis, mating and fertilisation
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Which chromosomes determine the sex of an organism?
The 24th pair; either ** (females) or XY (males)
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When do sexual differences begin to emerge?
In the 6th week of foetal development
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Before week 6, what is the state of the foetus?
Both males and females foetuses have the precusor gonadal tissue for making the gonads (testes or ovaries)
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What determines the foetus becoming a male?
The presence of the SRY (sex-determining region of Y) gene on the Y chromosome
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What does SRY produce?
A protein called; testis-determining factor (TDF), which causes the gonadal tissue/ridge to develop into testes
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What occurs in the absence of the SRY gene on the Y chromosome?
The foetus begins to develop ovaries around the 7th week
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What is an androgen?
A male sex hormone
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What sex hormones do the testes produce?
Testosterone and Mullerian-inhibiting Substance (aka. anti-mullerian hormone)
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What does testosterone do?
Testosterone- masculinises the male sex organs (developing the wollfarian duct system into the male internal sex organs
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What are the internal male sex organs?
Vas deferens, seminal vesicles and prostate
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What does Mullerian-inhibiting substance do?
Causes the mullerian ducts (female) to degenerate and the wolffian duct (male) to grow
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What is the Wolffian duct?
A duct with the potential to develop into the male internal sex organs
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What is the Mullerian duct?
A duct with the potential to develop into the female internal sex organs (uterus, fallopian tubes and upper vagina)
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What are the wolffian and mullerian duct connected to?
The precuror gonadal tissue
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What causes the mullerian duct system to grow?
A lack of endocrine stimulation (also causes wollfian duct system to degenerate)
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When does the external genital anatomy begin to show?
Around week 8-12
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What are the genitals of males?
Penis and scrotum
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What are the genitals of females?
Vagina, labia and ********
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What does the release of testosterone do?
Acts on epithelial tissue causing the male organs to form
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What does the lack of testosterone release do?
Causes the female male organs to grow
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What more potent form of an androgen is testosterone turned into?
5-alpha-dihydrotestosterone
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Which enzyme carries out this conversion?
5-alpha-reductase
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What is 5-alpha-dihydrotestosterone important for?
The differentiation between the penis and scrotum
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Which sex has more androgen receptors, and which has more estrogen receptors?
Males- more androgen receptors & females- more estrogen receptors
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What is cogenital adrenal hyperplasia?
A recessive condition that occurs when a female is prenatally exposed to high levels of testosterone/adrogens e.g. anabolic steroids
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What is the result of cogenital adrenal hyperplasia?
Masculinisation of the female genitals (newborn w/ small penis, surrounded by skin folds ressembling a poorly formed scrotum)
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What are females(pseudo-hermaphrodite) with this condition like?
"Tom-boy", engage in male-typical play, perform well on cognitive tasks that favour males e.g. spatial puzzles, more likely to be homosexual/bisexual
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What is the cause of cogenital adrenal hyperplasia?
Foetal adrenal glands don't produce enzyme 21-hydroxylase (helps makes cortisol). Adrenal glands start secreting high levels of androgens
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What is Androgen-insensitivity syndrome?
When androgen receptors are insensitive to the effects of testosterone
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What are the effects?
Sufferer develops normal testes but develops the external sex organs of a female (********, vagina and labia)
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What are the 2 types of effects hormones exert?
Organisational and activational
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What are organisational effects?
The effect of horomones in determining sex and organising the structure of the brain for later adult behaviour
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What are activational effects?
The effect hormones have on behaviour (by gonadal hormones acting on the brain)
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What are the activating effects of testosterone?
Aggression, courtship, rough and tumble play and taste preference
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What are the activating effects of hormones in females?
The control of the menstrual cycle
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What is the final stage of sexual development?
Puberty
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What is the most important event causing puberty?
The release of sex hormones from the gonads (testosterone from testes; progesterone and oestrogen from the ovaries)
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Where in the brain does the trigger for puberty come from?
The hypothalamus and pituitary gland (when they begin to control the gonads)
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What does the hypothalamus secrete?
GnRH (gonadotropin-releasing hormone)
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What does GnRH diffuse through?
The hypophyseal portal blood vessels into the anterior part of the pituitary gland
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What does the hormone then cause?
The pituitary gland to release; LH (luteinising hormone) and FSH (follicle-stimultating hormone), into the bloodstream and transported to the gonads
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What happens in males?
The release of LH causes leydig cells of the testes to make testosterone and FSH stimulates the production of sperm
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What happens in females?
LH stimulates the production of oestrogen and FSH causes the secretion of progesterone from the corpus luteum
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What did Phoenix et al. found?
He found that a female guinea pig who had been exposed to high levels of testosterone during early development, did not show lordosis when induced with oestrogen and progesterone
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What happened to female rats postnatally exposed to testosterone?
They did not show lordosis, but mount females
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What happens to male rats postnatally castrated?
Displays lordosis to male rates, and does not mount females
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Other cards in this set

Card 2

Front

What are the 3 fundamental steps of sexual reproduction?

Back

Gametogenesis, mating and fertilisation

Card 3

Front

Which chromosomes determine the sex of an organism?

Back

Preview of the front of card 3

Card 4

Front

When do sexual differences begin to emerge?

Back

Preview of the front of card 4

Card 5

Front

Before week 6, what is the state of the foetus?

Back

Preview of the front of card 5
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