hormones and behaviour Flashcards
what causes hunger
leptin ( not hungry) and ghrelin (hungry)
where is leptin released from
-specialised fat-storage cells
-the more fat storage cells the more leptin released into blood
-leptin sends signals to hypothalamus for less hunger
when is ghrelin released
-if leptin levels are low
-released from stomach for more hunger
behavioural endocrinology
-hormones play a big role in development of structure e.g. glands
-hormones can have activation effects e.g. altering neural networks
-hormones underpin timing of reproduction when conditions are most favourable
what do internal clocks do
regulate behaviour, all animals have them
types of internal clocks
1) very short: locomotion e.g. heartbeat
2) circadian: 24h, resting or foraging
3) circa lunar: 1 month, menstrual cycle
4)circannual: 1 year, migration, reproduction
what are clocks essential for
-navigation using sun or stars
-timing of migration
-foraging
-breeding
what are the two hypotheses for rhythms
1) environment-independent timing mechanisms
-predicts that animals will continue to have the same rhythms irrespective of the environment
2) environment-dependent timing mechanisms
-predicts individual rhythms can be reset by changes in the environment
environment- independent control test
-take away all possible external stimuli (light temp) and keep animals in isolation and in a constant environment
-results: individuals have various forms of rhythms
evidence of circannual rhythm in golden-mantled ground squirrel
-used 5 individuals for this experiment
-gave us a good insight on how circannual rhythms work
-constant light and temperature was used
-golden-mantled ground squirrel have a year long circannual rhythm
environment-dependent control example
-jetlag resolves itself as internal clock resets itself to new conditions
invasive experiments showing how internal clocks work
-x optic nerve- ability to maintain rhythm but inability to change it to new environment (take away info from their eyes)
-x optic lobe- rhythm breaks down (lobe is disconnected and this is key to how the rhythm is maintained)
-no melatonin produced
how is the production of melatonin inhibited in humans
sunlight to eye which sends signal to the optic nerve which is received by the optic lobe. signal then sent to pineal gland which inhibits melatonin
-process the same in all animals
naked mole rats
-not dependent on anything above ground
-their normal day just consists of foraging
-they have no regular rhythm
-live in colonies underground for their whole life
-feed on roots
-similar to honey bees as they have a queen who does all the reproducing
what’s endocrine action
hormones secrete into the blood
whats paracrine action
hormones diffuse across cells
why is migration an example of importance of clocks and hormones: fat deposition
feed a lot and all food turns into fat for winter periods when they migrate
why is hibernation an example of importance of clocks and hormones: fat deposition
animals can stock themselves up with food for autumn months so they can survive hibernation- this is a behavioural change as more food is being eaten
importance of clocks and hormones: reproduction
-prolactin can influence individuals by making them more parental
-without progesterone the body can’t maintain pregnancy as the progesterone levels drop before giving birth to tell body that the body doesn’t want to be pregnant anymore
importance of clocks and hormones: infanticide
-crocodiles: birth offspring and they stop eating as they don’t want to eat its offspring- this is due to prolactin
-mouses: male mouses are aggressive to mice pups but turn parental after sex but after 7 weeks turns back aggressive as it kills any pups that aren’t his- due to female insemination of someone else
motivation to mate controlled by hormones
-in mammals and birds
-in female Rhesus monkeys motivation to mate is greatest at point in her estrus cycle when the hormone oestrogen peaks
-mating isn’t a physiological balance like hunger
-hormonal drives are always present- need to be switched off
sex peptides in drosphillia
-after copulation, egg laying rate increases and sexual receptivity of females declines
-advantageous for female to mate with more than one male
-males might not be the father hence why they don’t mate as much
-sex peptides cause behavioural changes which are transferred with sperm during insemination- detected by sensory neurones in uterus
effects of copulation in green anole- anolis carolinensis
-red chin is their way of showing courtship behaviour
-mechanical stimulation of females genital contract during copulation stimulates production of prostaglandin (becomes abundant in females blood streams)
