Hormonal control of development and behaviour

Major glands in the body

pineal, hypothalamus, pituitary, adrenal, pancreas, ovary, testis

Testosterone is produced by

testis and adrenal gland so females have testosterone as well

Hypothalamus controls the

release of hormones by the other glands within the body

Brain releases hormones into the blood via

the pituitary gland

The hormones released from pituitary glands result in

stimulating release of other hormones by glands throughout the body

Anterior pituitary is mostly controlled by

chemicals that are released by hypothalamus into blood

posterior pituitary is controlled by

neurons and is like an extension of the hypothalamus

Hypothalamus releases…, anterior pituitary releases….,

gonadotropin-releasing hormone, gonadotropin,

gonads release…

estrogens’s, androgens and progestins

2 important times when we release gonadotropic from hypothalamus:

1. While foetus is developing within mother

2. During puberty. Affect testes and cause massive release of testosterone or massive release of estradiol from ovary

How many genes are on a Y chromosome?

only have 500 genes in Y chromosome but it does have SRY gene which controls the production of testes

At 6 weeks of age the gonads are

no different in males and females

because of the Y chromosome SRY gene then the male gonads…

turn into testes whereas in absence of SRY gene than female gonads will change into ovaries

Different systems in males and females

Wolfian (male) or mullerian (female) systems

Testes releases (other than testosterone)

anti mullerian hormone which gets rid of the mullerian system

There are no hormones that control development of

ovaries it automatically develops.

The conversion of testosterone to…

dihydrotestosterone (DHT) leads to differentiation of external genetalia

More info on DHT

DHT has 2 extra water molecules and basically the same thing as testosterone.

The conversion of testosterone to DHT by an enzyme.

Without DHT female genitiillia will develop

gender differences in brain size

Men's brain 15% larger than Women's brains because men are on average 15% larger in body size

Gender differences in brain: Women's hemisphere's share

more functions than men. Eg: females are more likely to compensate for damage to brain and recover speech because their brain is more plastic and shares more functions on either side of the brain

Gender differences in brain: related to hypothalamus

Different size in Medial preoptic area of hypothalamus

Sexually dimorphic nuclei in the preoptic area

there is more sexually dimorphic nuclei in the male one than in the female one.

When the female was injected with testosterone there was increases in

the number of sexually dimorphic nuclei

De Jonge et al (1989) found that lesions of the

SDN decrease masculine sexual behaviour

Warne & Zajac, 1998 - masculinity

Masculinity of brain is caused by Estradiol

What can get through the blood brain barrier in male brains?

estradiol can but testosterone can’t

What produces estradiol?

Aromatization of testosterone because both hormones have similar structure. So Blocking aromatization blocks masculinization

Human females protected from mothers estradiol by

• placenta

• So females don't produce estradiol until their puberty so this doesn't masculinise the brain

Alexandra and Hines(2002) procedure

Put loads of toys into the cages with the monkeys

Alexandra and Hines(2002) results

• male monkeys much more likely to play with cars and female monkeys were much more likely to play with dolls

• So it must be due to biological factors

Organisation and activation effects procedure

• Immediately after birth of rats they were either given testosterone or nothing

• When fully grown either given injection of oestrogen & progesterone or testosterone

Organisation and activation effects results

• female rats given no injection immediately after birth and injection of oestrogen displayed female sexual behaviour and this is an indication of activation of oestrogen- they didn’t had to have hormones changing the brain but had to have oestrogen at puberty to result in female sexual behaviour

• When no hormones immediately after birth and injected with testosterone at puberty then there is no female or male activity suggesting you need organisational effect on the brain for testosterone to take effect

 

Androgen insensitivity syndrome

• XY individuals with this disorder are not sensitive to testosterone.

• The wolffian system does therefore not develop

Androgen insensitivity syndrome - what hormone are they sensitive to?

sensitive to the anti-mullerian hormone which is not an androgen. This means the mullerian system doesn't develop either leaving the individual with no internal reproductive system

Androgen insensitivity syndrome - what other hormone are they not sensitive to?

external genitalia are also not sensitive to DHT but the external genitalia will continue to develop as female genitalia meaning the individual will have external female features

Congenital Adrenal Hyperplasia

• Females have testosterone due to adrenal gland. But the adrenal gland goes into overdrive and produces loads of testosterone

Turner's syndrome

• Results from abnormal sex chromosomes so have XO chromosome

• Neither ovaries or testes develop

• Individuals develop normal female internal sex organs and external genitalia

Persistent Mullerian duct syndrome - caused by

• Either a failure to produce anti-mullerian hormone or the absence of receptors for this hormone (Warne & Zajanc, 1998)

Persistent Mullerian duct syndrome - this results in

• Both sets of internal sex organs, male and female, develop

• The presence of the additional female sex organs usually interferes with normal functioning of the male sex organs

Shabir et al, 2015 - Deficiency of the 5a-reductase 2 enzyme

(which changes testosterone to dihydrotestosterone) impairs the differentiation of external genitalia

5a-reducatase deficiency

have male organs internally but not externally

5a-reducatase deficiency - The massive second release of testosterone will be

• enough to the create the dihydrotestosterone to change external genetala to being male.

• They only form a penis at about 12 years old

Behavioural differences due to hormones: cortisol

Maternal stress causes release of cortisol

Medial preoptic area (MPA) of the brain, normally larger in…

males than females, is reduced in male rats born to stressed mothers

Male rats born to stressed mothers are less likely to display..

male sexual behaviour (ward, 1972). As the MPA is important in male sexual behaviour

Luplante et al, 2008: Ice storm in canada - children exposed in utero to high levels of

 objective stress had lower full scale IQs, Verbal IQs and language abilities compared to children exposed to low or moderate levels of objective prenatal maternal stress

Does sitting next to males make you angry? - Vom Saal & Bronson, 1980

Being next to a male foetus increases female blood levels of testosterone

2M females are more likely to

engage in inter-female aggressiveness. 2M females refers to when they are in the womb they are next to 2 males.

Van de Poll et al, 1988

• Injecting testosterone immediately after birth and when female rat is fully grown caused aggressive behaviour

• Injecting Estradiol had the same levels of aggressiveness as placebo

Money & Ehrhardt, 1972 - testosterone

Reduction in testosterone levels leads to reduction in sexual behaviour

Hellhammer et al (1985) - sex

Thinking about sex increases levels of testosterone

• And it makes you grow a beard faster (Anonymous, 1970)

Grunt & Young, 1952 - procedure

Used Guinea pigs and ranked them in order from most to least sexually active, castrated them and injected them with same level of testosterone.

Grunt & Young, 1952 - a few months later

measured and rated them again from most to least sexually active and found it was the exact same list as previously

Carter, 1992 - androgens

Androgens produced by adrenal gland, prostate gland and fat tissue

Foster et al, 1990 - oxytocin

oxytocin is responsible for refractory period - period when males weren't able to have sex

Rimmele et al, 2009 - oxytocin

If have increase in oxytocin after having sex this will increase your reward centres. Oxytocin increases memory faster for faces (so increases pair bonding) but not nonsocial stimuli in both men and women

Destruction of premedial optic area in rats causes

abolishment of sexual behaviour but if inject testosterone into area then sexual behaviour will happen again

Morries et al, 1987 - ovarian hormones

Fluctuations in ovarian hormones showed little correlation with sexual activity

Matteo & Rissman, 1984 - lesbian couples

Study of Lesbian couples found significant increase in activity during synchronised ovulation

Allyn & Bacon (2004)

• In Heterosexual relationships it will be the males initiating sex but just before ovulation it was females initiated sex.

What is Allyn & Bacon (2004) results due to?

 testosterone released from adrenal gland highest just prior to ovulation.

Premedial optic area in females

smaller in females than males and is more to do with parental behaviour rather than sexual behaviour.

What controls female sexual behaviour?

Ventromedial nucleus of hypothalamus

McClintock, 1971

Women attending all female college had synchronised cycles

Wyart (2007) - sweat

showed women exposed to androstadienone (AND) found in men's sweat raised attention and mood while for men it increases drowsiness and decreased positive mood

Savic (2001) - sweat

showed AND activated the MPA and VMH in women but not in men, an estrogenic chemical had similar results for men

Singh and Bronstad (2001) found that males reported sweaty t-shirts from a female in

fertile cycle rated more pleasant than other parts in cycle. This would increase their chance of offspring.

Wedekind et al, 1995. Females preferred t-shirts of males that had

different immune systems to themselves. If you have different immune system then offspring is more likely to survive.

Money, Swatz and Lewis, 1984 - CAH

Study on 30 women with CAH reported incidence of homosexuality 4 times higher than in wider population

3 hormones involved with control of maternal behaviour:

prolactin, progesterone and Eostrodial

Voci and Carlson, 1973 - prolactin

Prolactin stimulates nest building in females

Van Leengoed et al (1987) - maternal behaviour

showed reduced maternal behaviour in animals treated with oxytocin antagonist

An fMRI study (Bartels & Zeki, 2004) found that when mothers…

looked at pictures of their infants, brain regions involved in reinforcement and those than contain receptors for oxytocin showed increased activity

Kirkpatric et al (1994) - prairie voles

showed activation of neurones in MPA when male prairie voles are exposed to pups. MPA within prarie voles is acting like the MPA in human females

Fleming et al (2002) found that fathers with

higher blood levels of prolactin reported stronger feelings of sympathy and activation when they heard the cries of infants