Biology of Mating and Parenting Flashcards
Primary Sex Characteristics
- Present at birth
> Gonads - ovaries or testes
> External genitalia
> Internal sex organs
Secondary Sex Characteristics
- Appear at puberty
> Enlarged breasts, wide hips
> Facial hair, deep voice
Sexual Maturation
- Puberty occurs when hypothalamus secretes gonadotropin-releasing hormone (GnRH)
- Anterior pituitary releases gonadotropins
> Follicle stimulating hormone
> Luteinizing hormone
Sexual Maturation for Females
- Rising levels of gonadotropins stimulate ovaries to release estrogen
- Oestradiol responsible for secondary sexual characteristics
Sexual Maturation for Males
- Testes release Androgens
- spermatogenesis is initiated and then sustained by FSH and testosterone as puberty progresses
Oestradiol and Androgens
- Halt skeletal growth
Oestrus Cycle
- Most mammals
> eg. cats, horses, dolphins, giraffes
FSH
- Anterior Pituitary gland
> Stimulates follicular growth in ovaries
> Stimulates estrogen secretion
LH
- Anterior Pituitary gland
> Surge causes ovulation
> Results in formation of a corpus luteum
Estrogen
- Ovaries
> Thickens uterine lining
> Inhibits FSH, LH for most of cycle
> Stimulates FSH and LH release pre-ovulation
Progesterone
- Ovaries
> Thickens uterine lining
> Inhibits FSH and LH
Ovulation
- Ovarian follicles ruptures releasing the ovum
- Ruptured Ovarian Follicle becomes Corpus Luteum
Corpus Luteum
- Produces Oestrogen and Progesterone
- Embryo produces hCG
- If egg not fertilised then oestrogen and progesterone levels fall
> Uterus produces prostaglandins which cause uterus to contract, marking start of menstruation
Hormonal Effects on female sexual behaviour
- Oestrogen and Progesterone control willingness to mate
- Oestrous cycle mammals - not interested and can only get preg when ‘in heat’
Female human sexual behaviour: Adams, Gold, Burt (1978)
Morris et al (1987)
- Studied sexual interest in women
- Fluctuations in hormone level showed no effect on sexual behaviour but did in sexual interest
Female Human Sexual Behaviour: Matteo and Rissman (1984)
- studied lesbian couples
- mensteral cycles likely to be synchronised
- increase in sexual interest and activity during middle of cycle
- ovarian hormones influence female sexual interest
Female Human Sexual Behaviour: Van Goozen (1977)
- women did instigate more sexual activity around ovulation
Female Human Sexual Behaviour: Slob et al (1996)
- women rate an erotic video as more pleasurable and stimulating if they watch during periovulatory period
Female Human Sexual Behaviour: Wallen (2001)
- sexual desire may not lead to sexual beh due to women not instigating or worry about pregnancy
Hormonal effects on Male sexual behaviour
- Bagatell et al (1994)
- gave placebo or gonadotrophin releasing hormone antagonist to young male volunteers
- 2 weeks later those given antagonist reported decreased sexual interest, fantasy and intercourse
Male Sexual Behaviour: Wallen et al (1991)
- injected GnRH antagonist in male rhesus monkey
- injection suppressed testosterone secretion and sexual behaviour declined after one week
- decline related to social rank & experience
- highest ranking male continued to copulate and ejaculate at same rate but not lower social ranking monkeys
Male Sexual Behaviour: Hellhammer et al (1985)
- found watching an erotic film increased men’s testosterone levels
Male Sexual Behaviour: Anonymous (1970)
- stationed on remote island
- shaved and weighed beard clippings
- before came off island (in anticipation of returning to loved one) beard grew faster
Pheromones
- chemicals released by one animal
- affects the behaviour of physiology of another
- some of these chemicals affect reproductive physiology and beh
- in Mammals most pheromones are detected by olfaction
Pheromones Physiological Effects: Lee-Boot effect (van der Lee and Boot, 1955)
- when female rats are housed together, their oestrus cycles slow down and eventually stop
Pheromones Physiological Effects: Whiten effect (1959)
- if groups of females are exposed to the odour of a male they start cycling again and their cycles tend to be synchronised
Pheromones Physiological Effects: Vandenbergh effect (1975)
- early onset of puberty in female rats housed with males
Pheromones Physiological Effects: Brace effect (1960)
- pregnancy of a recently impregnated female mouse is likely to fail if she encounters a male other than the one she mated with.
Pheromones Behavioural Effects
- pheromones located in vaginal secretions of female hamsters stimulate sexual behaviours in males
- some pheromone related phenomena also occur in humans
Pheromones in Humans: McClintock (1971) all female college
- studied menstrual cycles of women attending all-female college.
- women who spent large amount of time together tended to have synchronised cycles
- women who regularly spent time in presence of men tended to have shorter cycles than those who rarely spent time with men
Pheromones in Humans: Russell, Switz and Thompson (1980) sweaty arm pits
- collected daily samples of women’s underarm sweat
- dissolved samples in alcohol and swabbed them onto upper lips of groups of women (3 times a week)
- menstrual cycles of receivers become synchronised with the cycles of the donors
Pheromones in Humans: Russell (1976) smelling T-shirts
- participants could distinguish between T-shirts they had worn and those previously worn by other people, by smell alone
- could identify gender of the wear too
Maternal Behaviour
- Kaitz,1987
- one most surprising abilities of new mothers is ability to recognize their child on the basis of smell
Maternal Behaviour: Monkeys
Maestripieri and Zehr (1998)
- pregnant monkeys become more interested in baby monkeys as their pregnancy progresses
Mayer and Rosenblatt (1984)
- hormones produced late in pregnancy make females less responsive to infant rats
- after delivery, mother rats, monkeys and all mammalian species become highly attentive to their own young
A newborn rat or mouse
- resembles a foetus
- cold blooded
- eyes shut
- can not move
- can not release urine or faeces
Rat maternal behaviour
Prepartum
- nest building
Postpartum
- retrieval
- licking
- maternal aggression
Pre Partum: Nest Building
-facilitated by progesterone
Lisk et al (1969)
- gave progesterone to non-pregnant females causing NEST BUILDING
- gave oestrogen, which STOPPED IT
Voci & Carlson (1973)
- progesterone and prolactin facilitated nest building
Partuation
- female rat licks the area around her vagina
- pups born she aids contractions by pulling them out
- eats placenta
- cleans foetal membranes from the pup
Partuation: Yeo and Keverne 1986
- simulating birth by extending birth canal in non pregnant rats stimulates maternal behaviour
- removing afferent nerves from birth canal decreases maternal behaviour
Progesterone Drop at Parturition
- hysterectomies on pregnant rats – stops release of progesterone.
- placed pups near the rat
- ontrol group of non-mothers ignored pups
- hysterectomised rats did show maternal behaviour
- later in pregnancy rat is hysterectomised, the greater effect is
- supports Rosenblatt’s theory
Rosenblatt cont. 1
- each stage pregnancy, ovariectomy reduced effect of hysterectomy
- rats that are given the double operation take longer to develop maternal behaviours than animals only given a hysterectomy
- suggests presence of high oestrogen levels against background of low progesterone levels stimulates maternal behaviour at end of a normal pregnancy.
Rosenblatt cont. 2
G1: Hysterectomised - progesterone declines, normal oestrogen level.
G2: Hysterectomised + ovariectomised - progesterone declines, source of oestrogen removed
G3: Hysterectomised + ovariectomised + oestrogen injection - progesterone declines, source of oestrogen removed and then replaced with oestrogen injection.
G1- maternal beh
G2- longer to exhibit maternal beh
G3- injection of oestrogen overcomes effect of ovariectomy and restores rapid onset of maternal beh
Oxytocin
- powerful hormone that acts as a neurotransmitter in brain
- regulates social interaction and sexual reproduction
- role in beh from maternal-infant bonding and milk release to empathy, generosity, and orgasm
- huge role in all pair bonding
- greatly stimulated during sex, birth, and breastfeeding
- hormone that underlies trust.
Oxytocin: Pedersen et al (1982)
- virgin female rats received an injection into ventricles of the brain
- given 48 hours after ovariectomy and priming with oestrogen
- 85% of rats treated with oxytocin were maternal
- 18% of control rats were maternal
Oxytocin: Pedersen et al (1994)
- drugs that block action of oxytocin prevent mother rat from gathering her young into the nest and nursing them
- oxytocin could be responsible for rapid initiation of maternal behaviours seen shortly after parturition
Neural Control Of Maternal Behaviour
- medial preoptic area (MPA) appears important for maternal beh
- Numan (1974) found lesions of the MPA disrupted nest building and pup care
