Hormones and behaviour Flashcards
how do hormones influence behaviour?
biological rhythms
eating and drinking
reproductive behaviour
social behaviour
stress
the pineal gland
unusually, an unpaired structure
in birds and reptiles, can sense light directly through the skull
in mammals acts via cervical ganglia
phasic (cf. tonic) secretion of hormones and other chemicals in cyclic patternshourly, diurnal, monthly, seasonally…
melatonin is important in regulating cyclical functions
what is melatonin?
released almost exlusively at night
provides a signal to track daylength and season
controls the timing of onset of sleep (in humans)
controls breeding condition in seasonally breeding animals
example of melatonin
breeding condition in hamsters
breeding in hamsters in the autumn
- senses longer autumn nights
- pineal gland prolongs nocturnal secretion of melatonin
- hypothalamus becomes sensitive to -ve feedback effects of gonadal steroids
- less GnRH released
- less gonadotropin released, so gonads atrophy
breeding in hamsters in spring
- senses shorter spring nights
- pineal gland reduces nocturnal secretion of melatonin
- hypothalamus becomes less sensitive to -ve feedback effects of gonadal steroids
- more GnRH released
- more gonadotropin released, gonads swell and animal prepares to breed
what is ghrelin?
28-amino-acid peptide secreted by cells in stomach epithelium
stimulates feeding
stimulates release of growth hormone (GH) from pituitary
ghrelin-secreting neurons in brain also involved in control of feeding
what happens to circulating levels of ghrelin?
rise prior to mealtimes and at night
drop following a meal
how do you provoke increased appetite?
treatment with exogenous ghrelin
obese people and ghrelin
have lower ghrelin before eating
but following a meal their levels do not drop
→ a ghrelin system unresponsive to feeding and therefore always hungry?
what happens during the mammalian oestrous cycle?
Cyclic patterns of gonadotropin secretion (FSH, LH), present only in females, prompted by surge in GnRH (from hypothalamus) above tonic levels
Effects behavioural as well as physiological changes
pro-oestrus
follicular development and ovulation
oestrus
receptive period during which fertilisation is most likely to lead to pregnancy
sexually active here
Beall and Tracy (2013)
N = 124 normally ovulating women, aged 17–47 (undergrad + community samples)
asked on-line what colour shirt they were wearing
classified as high fertility or low fertility based on reported time since last period
Miller et al (2007)
recorded tip earnings by dancers in lap-dancing club
dancers provided information on their menstrual cycle and use of hormonal contraception
types of social behaviour
affiliative behaviour
generosity
orgasm
trust
parental care
what is oxytocin?
a mammalian peptide hormone that acts on the central nervous system
generally associated with uterine muscle contraction at birth and milk letdown
also governs a suite of prosocial behavioursas do analogues (e.g. isotocin) in other taxonomic groups
what is parental care?
own young
female rats bred for high levels of maternal behaviours have more oxytocin receptors in the central nucleus of their amygdala
female prairie voles that show more maternal behaviour have higher oxytocin receptor density in their nuclear accumbens
blocking these receptors inhibits maternal behaviour
what is alloparental care?
young of others
neonate female prairie voles injected with oxytocin are less likely to attack novel stimulus pups
neonate male prairie voles injected with an oxytocin antagonist show reduced alloparental care
social behaviour in meerkats
allonursing
sentinel duty
pup feeding
digging
Madden and Clutton-Brock (2010)
N = 36 meerkats (28 males, 8 females) injected with oxytocin vs saline control
treatments reversed 3–5 days later
recorded suite of prosocial behaviours
also recorded initiation of aggression
effects only lasted for about 30 mins
what is affiliative behaviour ?
rodents and meerkats given supplementary doses of oxytocin spend more time in contact with others
‘knocking out’ oxytocin gene of male mice renders them unable to recognise scent of previously encountered female
infusing brain with oxytocin cures this amnesia
prairie vole pair bonding
monogamous male mates with one female
oxytocin injections promote pair bonding
dense collection of vasopressin receptors
meadow vole pair bonding
polygynous male mates with multiple females
no pair-bonding
few vasopressin receptors
social behaviour in humans
trust
generosity
social sensitivity
orgasm
Kosfield et al. (2005)
2-player economic ‘trust’ game
investor and trustee each receive 12 monetary units
investor chooses to send 0, 4, 8 or 12 MU to trustee
amount sent is tripled by experimenter
trustee chooses how much of total to send back
N = 194 healthy male participants
3 puffs per nostril of oxytocin vs control (double-blind) 50 mins before playing game
Those who received oxytocin made transfers ~17% higher than control group
Zak et al. (2007)
N = 68 men
‘one-shot’ economic game involving a voluntary donation
given oxytocin vs control via nasal spray
donations were ~80% higher in oxytocin group
Marsh et al. (2010)
used well-validated set of photos of facial expression
blended with neutral expression to create varying emotional intensity
participants classified expression 35 mins after oxytocin vs control nasal spray
→ oxytocin increases sensitivity to positive emotional expression
orgasm
plasma oxytocin increases during orgasm—in males and females
plasma oxytocin levels increase during self-stimulated orgasm
oxytocin evokes feelings of contentment, reductions in anxiety and feelings of calmness and security around mate (trust and generosity?)
may indicate that sex promotes pair bonding
the endocrine system
chemical substance
conveyed in blood
diffuse effect across body
analogue (graded) signal
‘slow’ response (secs or mins)
response persists over time
no voluntary control
the NS
action potential
transmitted along nerve fibre
targeted effect in specific cell or organ
digital (all-or-nothing) signal
fast response (ms)
responses generally short-lived
some voluntary control
both the endocrine and NS
Both are communication and control systems
Both take inputs and effect outputs
Both can be influenced by prior exposure (habituation/immunity)
the neuroendocrine system
Fast initial response
Prolonged action if required
Enables regulation and control of homeostasis
- CNS
- ANS
- SNS and PSNS
Ensures that the appropriate response is given to a stimulus
