testosterone case study Flashcards
what can testosterone do
-promotes sperm production
-activates sexual behaviour
-suppresses immune system
-modulates aggressive behaviour
where does testosterone come from
-produced in testes in interstitial cells
-produced in response to a glycoprotein produced in he anterior pituitary in brain
-T transported in blood stream
what’s the role of testosterone
-response for most secondary sexual characters
-e.g. cockerels wattles- tested experimentally by removing testes and then replacement of testosterone
-testosterone shot given and comb grows back
guinea pig and sex drive
-decreases after castration therefore showing T levels re closely linked to testosterone
-after T shot, sex drive increases again which is a behavioural response
what does endogenous mean
within baseline levels
testosterone and aggression in humans
-individuals with higher endogenous levels of T are more likely to be aggressive and dominant
-T levels increase in anticipation of aggression and after and aggressive incident
challenge hypothesis
-explains variation of T in birds
-some birds are more aggressive than others
-a challenge is an aggressive encounter which increases T levels
-experiment: 4 different song sparrows and they chose the territories which were closer together, A takes one territory, then B tries to take over that territory leading to increase T levels in the areas surrounding this territory but the areas surrounding the increased T levels is normal
T and aggression in females
-females can produce T in ovaries
-female songbirds have T and if T levels is elevated they will sing
-example: dunnocks prunella modularis, two females and one male, females then compete with one another to mate with the male
-males tend to have only one mate to ensure their paternity
-females have more T when competition comes into play
T and parental care
-married fathers have lower T levels than unmarried non-fathers
-fathers who invest highly in parental care have lower T
-higher levels of T can cause the breakdowns of marriages
-decrease in T levels after child is born making the father a better parent
cost of T
-castrated men who don’t produce T due to no testes live 12 years longer than men who do produce T
side-blotched lizard- ute stansburiana
-3 males with alternative reproductive strategies
-orange: ultra-dominant+ high levels of T, have lots of territory with lots of females
-yellow: sneakers, don’t hold territories but hold clusters around the oranges ones can sneak in and mate with the females in the orange clusters
-blue: less aggressive and only guard one female
-oranges have lowest survival rate
fun fact about T
-the more T you have, the more likely you are to die earlier than those who have a lower level
