Lecture 6- Hormones II: Sex determination and behaviour

Question 1

hormones important for individual recognition and processing social cues

Answer 1

oxytocin, vasopressin

Question 2

how can pair bonds be triggered, hormonally

Answer 2

combination of neuropeptides (e..g oxytocin) and dopamine being active in the reward centres of the brain can lead to a pair bond after mating, concurrent activation can strengthen a partner preference

Question 3

what is vasopressin

Answer 3

also known as ADH, acts to increase water reabsorption in the kidneys. also has roles in social and sexual behaviour, pair bonding, maternal responses to stress

Question 4

important brain regions in pair bonding

Answer 4

Prefrontal cortex, nucleus accumbens and ventral pallidum- areas also involved more generally in dopamine reward systems

Question 5

how is sex determined in mammals

Answer 5

sex determining region of the Y chromosome- SRY, SOX9 lead to production of testes, ovary develops in the absence

Question 6

what is testosterone

Answer 6

a protohormone, which can develop into feminising or masculinising hormones

Question 7

sex determination in birds

Answer 7

msle homozygotes- known as ZZ- and female heterozygotes, oestrogens cause development into a female

Question 8

example of non-chromosomal sex determination

Answer 8

temp-dependent determination in reptiles
caused by the effect of temperature on enzymes involved in sex hormone action, such as aromatase

Question 9

what is aromatase

Answer 9

breaks down testosterone into feminising hormones

Question 10

effect of temp on sex determination

Answer 10

depends on the species- warm > males in lizards, warm > female in many turtles, middleish > male in crocodiles

Question 11

how do hermaphroditic fish change their sex

Answer 11

alternation of the ratio of sex hormones that are produced, e.g. parrotfish switch to male at a specific percentage of their total size

Question 12

example of different male morphotypes

Answer 12

midshipmen fish- type 2 males, mature earlier, but are smaller so appear female and can participate in ‘sneaky’ mating attempts

Question 13

how can you establish a causal link between hormones and behaviour?

Answer 13

blockade- hormonally-dependent behaviour will stop if you remove the hormone
reinstatement- restoration of the hormone should then reintroduce the behaviour
concentration dependence- reducing the concentration of the hormone should alter the extent of the behaviour

Question 14

example techniques

Answer 14

ablation- e.g. Berthold and the chickens
bioassay- injecting different doses of different hormones

Question 15

examples of prenatal androgen exposure

Answer 15

-female guinea pigs show suppression of female sexual behaviour, and performance of male sexual behaviour, shown by Young in the 50s
-can affect genital morphology in rats
-macaques- influence on rough play, masculinised genitals

Question 16

example to use talking about the menstrual cycle

Answer 16

peak in male-seeking behaviour in female rhesus monkeys around the mid-cycle oestrogen peak

Question 17

progesterone and social dominance

Answer 17

in goats- seemed to be more social dominance of goats w high progesterone, as this might make them more fecund

Question 18

progesterone in lizards

Answer 18

seems to regulate male-like sexual behaviour, whereas in oestrogen peaks more female-like behaviour is displayed

Question 19

example of testosterone influencing aggression and territoriality

Answer 19

-increase in T during the mating season in red deer, associated with more territoriality and mating behaviour
-aggressive behaviour quite correlated with testosterone in Egyptian spiny mice

Question 20

fish

example of something which can influence testosterone

Answer 20

cichlid fish- drop in testosterone following a defeat in territorial conflict