Hormones and Behaviour

Question 1

HORMONE ON BEHAVIOUR CONTEXTS

Answer 1

BIOLOGICAL RHYTHMS
EATING/DRINKING
REPRODUCTIVE BEHAVIOUR
SOCIAL BEHAVIOUR
STRESS

Question 2

BR: PINEAL GLAND

Answer 2

• unusually unpaired structure
• birds/reptiles sense light directly through skin
• mammals act via cervical ganglia
• phasic/tonic hormone/chemical secretion in cyclic patterns (ie. hourly/diurnal/monthly/seasonal)
• melatonin important in regulating cyclical functions

Question 3

BR: MELATONIN

Answer 3

• released almost exclusively at night
• provides signal to track daylength/season
• controls timing of human sleep onset
• controls breeding condition in seasonally breeding animals

Question 4

BREEDING CONDITIONS (HAMSTER EXAMPLE)

Answer 4

AUTUMN
1. senses longer nights
2. pineal gland prolongs nocturnal melatonin secretion
3. hypothalamus is sensitive to negative feedback gonadal steroid effects
4. less GnRH released
5. less gonadotropin released; gonads atrophy
SPRING
1. senses shorter nights
2. pineal gland reduces nocturnal melatonin secretion
3. hypothalamus is

Question 5

EATING

Answer 5

GHRELIN

• 28 amino-acid peptide secreted by cells in stomach epithelium stimulates feeding
• stimulates GH release from pituitary
• ghrelin-secreting neurons in brain involved in feeding control
• powerful appetite stimulant
• circulating levels ^ prior mealtimes/at night; drop following meal
• treatment w/exogenous ghrelin provokes ^ appetite
• obese people = lower ghrelin before eating BUT don’t drop post meal

Question 6

RB: MAMMALIAN OESTROUS CYCLE

Answer 6

• cyclic gonadotropin secretion (FSH/LH) patterns (only female) promoted via GnRH (from hypothalamus) surge above tonic levels
• pro-oestrus = follicular development/ovulation
• oestrus = receptive period during fertilisation most likely to lead to pregnancy
• most female mammals only sexually active during oestrous phase (“in heat”)

Question 7

REPRODUCTIVE BEHAVIOUR (EXAMPLES)

Answer 7

• female canids; blood-stained discharge from vulva turns straw-coloured to attract males
• female cats; “call” at night/roll/tread carpet/stand firm when pressure placed on pelvic region (lordosis)
• female rats; lordosis response when in oestrus; mount other females/more active than normal
• cows mount others (bulling)/bellow/are restless/discharge from vulva
• many primates; conspicuous red/pink sexual swellings

Question 8

RB: HUMAN FEMALE MENSTRUAL CYCLE

Answer 8

• fertile window = conception only likely if sperm present in reproductive tract when ovulation occurs
• effects behavioural/physiological changes
  BEALL & TRACY (2013)
• 124 pps; normally ovulating women 17-47y (undergrad community sample)
• asked online what colour shirt they’re wearing
• classified high/low fertility based on reported time since last period

Question 9

SOCIAL BEHAVIOUR

Answer 9

AFFILIATIVE BEHAVIOUR
TRUST
GENEROSITY
PARENTAL CARE

Question 10

SB: OXYTOCIN

Answer 10

• mammalian peptide hormone acts on CNS
• generally associated w/uterine muscle contraction at birth/milk let-down
• governs prosocial behaviour suite (like analogues (ie. isotocin) in other taxonomic groups)

Question 11

SB: PARENTAL CARE

Answer 11

• female rats bred as ^ maternal beh levels have more oxytocin receptors in central nucleus of their amygdala
• female prairie voles showing more maternal beh have higher oxytocin receptor density in nucleus accumbens
• blocking receptors inhibits maternal beh
  ALLOPARENTAL CARE (young of others)
• neonate female prairie voles injected w/oxytocin less likely to attack novel stimulus pups
• neonate male prairie voles injected w/oxytocin antagonist show reduced alloparental care

Question 12

SB: MEERKATS

Answer 12

MADDEN & CLUTTON-BROCK (2010)

• allonursing/sentinel duty/pup feeding/digging
• 36 pps (28m; 8f) injected w/oxytocin VS saline control
• treatments reversed 3-5d later
• recorded prosocial behaviour suite & aggression

Question 13

SB: AFFILIATIVE BEHAVIOUR

Answer 13

• rodents/meerkats given supplementary oxytocin doses spend more time in contact w/others
• “knocking out” oxytocin gene of male mice make them unable to recognise previously encountered female scent
• infusing brain w/oxytocin cures amnesia

Question 14

SB: PAIR BONDING

Answer 14

PRAIRIE VOLE
- monogamous 
- oxytocin injections promote pair bonding
- dense vasopressin (OT analogue) receptor collection
MEADOW VOLE
- polygynous 
- no pair-bonding
- few vasopressin receptors

Question 15

HUMAN SOCIAL BEHAVIOUR

Answer 15

• reciprocal relationship between hormones/beh
• naturally occurring hormone-beh correlations DON’T demonstrate causal effect
• placebo-controlled double-blind exps

Question 16

HSB: OXYTOCIN

Answer 16

BARTZ et al (2011)

• exogenous OXT administration + contextual factors + stable individual difs ->
• mechanisms = anxiety reduction/perceptual selectivity/affiliative motivation ->
• social effects = social cognition/pro-sociality

Question 17

HSB: TRUST

Answer 17

KOSFELD et al (2005)

• 194 healthy male pps
• 3 puffs p/nostril oxytocin 50min pre test
• 2 player economic trust game
• investor/trustee each receive 12 monetary units
• investor sends 0/4/8/12 MU to trustee
• amount sent tripled by experimenter
• trustee chooses how much of total to send back
• oxytocin = 17% ^ transfers than control

Question 18

HSB: GENEROSITY

Answer 18

ZAK et al (2007)

• 68 male pps
• one-shot economic game involving voluntary donation
• oxytocin VS control via nasal spray
• oxytocin = 80% ^ donations

Question 19

ENDOCRINE VS NERVOUS SYSTEM PROCESSES

Answer 19

ENDOCRINE
signal act -> endocrine cell -> hormones to bloodstream -> target cells
NERVOUS
pre-synaptic neuron -> action potential -> neurotransmitters over synapse -> post-synaptic neuron

Question 20

ENDOCRINE VS NERVOUS

Answer 20

• chemical substance VS action potential
• blood conveyance VS nerve fibre transmission
• diffuse effect across body VS specific cell/organ targeted effect
• analogue/graded VS digital (all or nothing) signal
• slow (s/m) VS fast (ms) response
• persisting over time VS short-lived response
• no VS some voluntary control
  BOTH
• communicative/control systems
• take inputs; effect outputs
• influenced by prior exposure (habituation/immunity)

Question 21

NEUROENDOCRINE SYSTEM

Answer 21

• fast initial response
• prolonged action if required
• enables homeostasis regulation/control (CNS/ANS/SNS/PSNS)
• ensures appropriate response to stimulus

Question 22

SUMMARY

Answer 22

• hormones affect beh across wide context range (bio rhythms/eating/reproductive beh/social beh/stress)
• oxytocin plays important role in mammal social beh
• placebo-controlled double-blind exps = useful for hormone effect on beh demonstration
• endocrine & nervous systems have important similarities/difs (mechanisms/timescales); also close connections (neuroendocrine)