Ch 8 Flashcards
Female and Male Motivations and Issues with Reproduction
Females (XX) ova and offspring require heavy investment. These are costly. Mating in the wrong conditions can be difficult. Motivation to be cautious.
Males (XY) sperm numerous and cheap. Little investment necessary. Risk of cuckoldry, risk of paternal confidence, infanticide if offspring not biological kin.
Mating and Bonding Systems
Monogamy: 1 male and 1 female for life. Dominant males lose, lower status males gain. Female-female competition for dominant males.
Serial monogamy: 1 male and 1 female on and off over time. Dominant males lose, lower status males gain. Female-female competition for dominant males.
Polyandry: 1 female and 2 males, lower status females lose, rare, males often tied by kinship.
Polygyny: 1 male and 2 females, dominant males gain and others lose, intermale competition intensified, lower status females gain from access to successful mates.
Polyamory: multiple committed relationships between males and females. Unique to humans.
Promiscuity: multiple casual relations, disease risk high, paternity uncertainty.
Mating and Bonding, Advantages and Disadvantages
Advantages: disease risk lower, bi-parental care opportunity, defense, provisions, higher quality offspring.
Disadvantages: exclusion of other opportunities, infertility, for males risk of cuckoldry and for females risk of abuse.
Attraction and Courtship
pheromones, visual stimuli and tactile stimuli all factor into sexual arousal. Courtship patterns vary by species. Sexual behaviour largely innate once initiated.
Shafik 1996
Rats wearing polyester pants generated electrostatic potentials which influenced intrapenile structures. This could explain the decrease in sexual activity.
Male Sex Hormone Synthesis
HT -> GnRH -> pituitary -> LH to Leydig cells to testosterone
Male and female sexual arousal and stress
Male sexual arousal facilitated by minor increases in stress. Female sexual arousal dampened even by little stress.
Female Sex Hormone Synthesis
HT -> GnRH -> pituitary -> LH to ovaries to estrogen
What does FSH do?
FSH releases inhibin which acts on the pituitary. It stimulates gamete production in males and females.
Males: stimulates spermatogenesis.
Females: stimulates follicle growth in the ovaries.
Inhibin under consideration as a male contraceptive.
The Pill
HT -> GnRH -> pituitary -> NO LH to ovaries, increased estrogen
Estrogen inhibits FSH and LH. No ovulation because no LH surge occurs.
Primates and Sexual Response
In many mammals, estrogen and progesterone control female sexual response. In primates like humans removal of adrenal glands reduce sexual interests.
Early Sexual Differentiation
- Bi-potentiality of primordial gonads. Absence of hormones causes Mullerian ducts to form and Wolffian ducts to degrade. Occurs in the first trimester 6-7 weeks.
- Masculinization: Wolffian ducts develop into epidydymis and vas deferens. Feminization: Mullerian ducts develop into uterus and uterine tubes.
- SRY gene on short arm of Y chromosome present in primordial gonads, releasing testis determining factor (TDF) and testes form.
- Embryonic testes release testosterone to stimulate Wolffian duct growth, with MIH hormone to suppress Mullerian ducts growth.
Differentiation in the ______ will impact sexual behaviour
Sexually dimorphic nucleus of the preoptic area (SDN- POA) of the hypothalamus. Larger in males.
- SDN-POA volume greatest in 2M males and lowest in 2F females.
___ is critical for male sexual behaviour, and ____ is critical for female sexual behaviour
preoptic area, ventromedial HT
* Lesioning the POA ends male sexual response for life.
Lesioning the VMH reduces female sexual receptivity.
_____ critical in maternal care
Medial POA of the HT
