Hormones and behaviour

Question 1

how do hormones influence behaviour?

Answer 1

biological rhythms

eating and drinking

reproductive behaviour

social behaviour

stress

Question 2

the pineal gland

Answer 2

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

Question 3

what is melatonin?

Answer 3

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

Question 4

example of melatonin

Answer 4

breeding condition in hamsters

Question 5

breeding in hamsters in the autumn

Answer 5

1. senses longer autumn nights
2. pineal gland prolongs nocturnal secretion of melatonin
3. hypothalamus becomes sensitive to -ve feedback effects of gonadal steroids
4. less GnRH released
5. less gonadotropin released, so gonads atrophy

Question 6

breeding in hamsters in spring

Answer 6

1. senses shorter spring nights
2. pineal gland reduces nocturnal secretion of melatonin
3. hypothalamus becomes less sensitive to -ve feedback effects of gonadal steroids
4. more GnRH released
5. more gonadotropin released, gonads swell and animal prepares to breed

Question 7

what is ghrelin?

Answer 7

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

Question 8

what happens to circulating levels of ghrelin?

Answer 8

rise prior to mealtimes and at night

drop following a meal

Question 9

how do you provoke increased appetite?

Answer 9

treatment with exogenous ghrelin

Question 10

obese people and ghrelin

Answer 10

have lower ghrelin before eating

but following a meal their levels do not drop

→ a ghrelin system unresponsive to feeding and therefore always hungry?

Question 11

what happens during the mammalian oestrous cycle?

Answer 11

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

Question 12

pro-oestrus

Answer 12

follicular development and ovulation

Question 13

oestrus

Answer 13

receptive period during which fertilisation is most likely to lead to pregnancy

sexually active here

Question 14

Beall and Tracy (2013)

Answer 14

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

Question 15

Miller et al (2007)

Answer 15

recorded tip earnings by dancers in lap-dancing club

dancers provided information on their menstrual cycle and use of hormonal contraception

Question 16

types of social behaviour

Answer 16

affiliative behaviour

generosity

orgasm

trust

parental care

Question 17

what is oxytocin?

Answer 17

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

Question 18

what is parental care?

Answer 18

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

Question 19

what is alloparental care?

Answer 19

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

Question 20

social behaviour in meerkats

Answer 20

allonursing

sentinel duty

pup feeding

digging

Question 21

Madden and Clutton-Brock (2010)

Answer 21

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

Question 22

what is affiliative behaviour ?

Answer 22

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

Question 23

prairie vole pair bonding

Answer 23

monogamous male mates with one female

oxytocin injections promote pair bonding

dense collection of vasopressin receptors

Question 24

meadow vole pair bonding

Answer 24

polygynous male mates with multiple females

no pair-bonding

few vasopressin receptors

Question 25

social behaviour in humans

Answer 25

trust generosity social sensitivity orgasm

Question 26

Kosfield et al. (2005)

Answer 26

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

Question 27

Zak et al. (2007)

Answer 27

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

Question 28

Marsh et al. (2010)

Answer 28

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

Question 29

orgasm

Answer 29

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

Question 30

the endocrine system

Answer 30

chemical substance conveyed in blood diffuse effect across body analogue (graded) signal ‘slow’ response (secs or mins) response persists over time no voluntary control

Question 31

the NS

Answer 31

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

Question 32

both the endocrine and NS

Answer 32

Both are communication and control systems Both take inputs and effect outputs Both can be influenced by prior exposure (habituation/immunity)

Question 33

the neuroendocrine system

Answer 33

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