Functionhormones
Functionhormones
Functionhormones
Hormone 1: Hormone 2: Melatonin & Sleep, Melatonin & SAD Oxytocin & Trust.
You need to make notes on the effects of each hormone on behaviour using the following headings:
What are hormones? What is melatonin (where is it made and secreted)? What are the effects of melatonin on behaviour (including studies to support claims) Discussion about melatonin (evaluation points e.g. application of this research) What is oxytocin? What are the effects of oxytocin on behaviour? Discussion about oxytocin (evaluation e.g. ethical implications of findings) Overview discussion drawing it all together
Summary:
Hormones
are chemical messengers that are secreted by glands and have a widespread effect on both physiology and psychology. The hormone melatonin is associated with the cycle of sleep, and the hormone oxytocin is known as the love hormone. These two hormones have different effects on human behavior.
Melatonin is the hormone associated with sleep and is secreted from the pineal glad at
the base of the brain. The increase in melatonin results in higher levels of sleepiness and tiredness. Its mainly secreted during the night and its main action is to communicate with the pituitary gland, which then inhibits the secretion of many other hormones in the body that relate to states of wakefulness. Therefore, melatonins role in the body is to turn off the wakefulness of the body.
Evidence suggests that higher levels of melatonin are linked to propensity to sleep, and
that higher levels of melatonin are associated with Seasonal Affective Disorder (SAD) which is a type of depression characterized by sleep disturbance and lethargy. Nevertheless, light therapy can be done to even out hormone secretion and improve sleep levels.
Oxytocin, otherwise known as the love or trust hormone, is a hormone that is produced
by the hypothalamus after being stimulated by the pituitary gland. It plays a role in inducing labor contractions and lactation, and is released with hugs and touches. Its also released when a womans nipples are stimulated, suggesting oxytocin has a role in human social bonding.
Evidence suggests that higher levels of oxytocin are linked to trust organism and
bonding, and that higher levels of oxytocin may reduce fear in the amygdala and increase trust. While this suggests that trusting and bonding behaviour is influenced by our hormones, we should not discount the influence of our thoughts, learning and society.
IB
Psychology
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BLOA
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Hormones
and
Behaviour
Notes
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Patricia
George
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November,
2012
Melatonin
Summary:
Melatonin is produced by the pineal gland, and is stimulated by darkness and inhibited by light Melatonin levels peak at night and decrease towards morning, Higher levels of melatonin are associated with propensity to sleep (Schochat et al. 1997) It is correlated with the 24-hour circadian rhythm As winter approaches, we get tired earlier and higher levels during darker days may correlate to SAD (Rosenthal 1987), lethargy, and cravings for carbohydrates
Humans have a very regular pattern of sleeping and waking. On average, humans spend
about 8 hours in every 24 asleep. For the remainder of the time they are awake. In general, humans (and many other animals) are very regular in their sleeping and waking times, always waking up and going to sleep at about the same time.
Endogenous Pacemakers and the Sleep-Wake Cycle The mammalian sleep-wake cycle is controlled by the suprachiasmatic nucleus (SCN), a small structure situated in the hypothalamus. The SCN is the bodys main circadian body clock. It generated a circadian rhythm independently of other brain structures. Darkness/lack of light is detected within the SCN. The darkness elicits electrical activity within the Pineal gland, which then releases Melatonin.
Sleep: increasing Melotonin Awake: increasing Cortisol Awake: increasing Temperature
Cortisol
Sleep time
Body
IB Psychology / BLOA / Hormones and Behaviour Notes / Patricia George / November, 2012
In birds and reptiles, the activity of the pineal gland is regulated by light. The pineal gland is light sensitive and birds and reptiles have thin skulls that daylight can penetrate. When light hits the pineal gland, melatonin production falls, and the animal wakes up. This is why birds tend to wake up as soon as it gets light. Humans and other mammals have thicker skulls, so they need the SCN to regulate the pineal gland. Melatonin production varies over a circadian cycle. It usually starts to increase between 8pm and 10pm, and most people feel sleepiest about 2 hours later. It begins to fall about 2am and reaches its lowest point around 7am. Melatonin is a naturally occurring hormone that is both endocrine (enters the bloodstream from a pineal gland) and paracrine (signalling cell phenomenon, as from the retina when light is low, when the signal is time to sleep). Besides being a sleep hormone, it is thought to be a very powerful antioxidant, anti-aging agent, immunoregulator and anti-depressant. It is closely related to (and may be involved in the production of serotonin). Fluctuations in melatonin explain why it is difficult to sleep outside your regular hours. If a person stays awake for much longer than usual, they may not be able to sleep because their melatonin levels are falling. People with damage to their pineal gland may find it difficult to sleep at all (Haimov & Lavie, 1996). Taking melatonin as a pill can affect sleeping patterns. If it is taken early in the morning, then the person will go to sleep later than usual. If it is taken in the afternoon, the person will sleep earlier than usual. If it is taken in the evening, it has little effect, because the persons melatonin levels are already high (Lewy et al, 1996). Research Study: Melatonin and Circadian Rhythm:
Schochat, T., Luboshitzky, R., & Lavie, P. (1997) Nocturnal melatonin onset is phase locked to the primary sleep gate; American Journal of Physiology, Volume 273, no 1, pages 364-370. Abstract available: http://0ajpregu.physiology.org.library.pcc.edu/content/273/1/R364.abstract
Aims: to investigate the involvement of Melatonin in the sleep-waking cycle Method: Six male participants in sleep laboratory between 7 a.m. one day to noon following day (29 hours). Used a very short sleep-wake paradigm, Participants spent 7 minutes in every 20 lying down in a darkened room trying to sleep. The period of greatest sleep propensity is known as the sleep gate. At different times throughout the day they measured participants tendency to sleep and melatonin by taking blood samples. Result: Demonstrated a close and precise relationship between propensity to sleep and melatonin levels, higher levels of melatonin = greater propensity to sleep. Increase in melatonin levels precedes the sleep gate by approx. 100 minutes (1 hour 2 hours) Conclusion: Provides evidence that there is a relationship between melatonin increase and propensity to sleep
IB
Psychology
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BLOA
/
Hormones
and
Behaviour
Notes
/
Patricia
George
/
November,
2012
Physicians recorded seasonal depressions as early as Hippocrates (400 B.C.). More recently, patients with regular seasonal depressions are labeled as having Seasonal affective disorder (SAD), which was a term invented by Rosenthal in 1984 and he noted the diagnostic criteria. SAD is described as a subtype of affective disorder (mood disorder, depression) with a seasonal pattern usually in the winter when sufferers experience clinical depression and has a greater prevalence in countries with greater northern latitude. Rosenthal et al. (1986) demonstrated that higher levels of melatonin contribute to SAD. Phototherapy is the main treatment for people with SAD, which involves exposure to bright light for several hours each day.
IB Psychology / BLOA / Hormones and Behaviour Notes / Patricia George / November, 2012
Avery et al (2001): provide indirect evidence for the role of melatonin in SAD: Method: Randomly assigned 95 SAD patients to three groups: Group 1 received dawn simulation beginning at 4:30am Group 2 received a more traditional bright-light therapy Group 3 received a placebo of a dim red light at dawn A structured interview was used to provide a depression rating specific to SAD Results: Groups 2 and 3 showed less improvement in symptoms and more side-effects than Group 1 (the dawn simulation group) Group 3 complained of more insomnia than the other groups at four weeks Conclusions: SAD symptoms are related to shifts in sleep patterns caused by a lack of daylight at the normal waking time. Bright-light therapy and dawn simulation helped to realign sleep patterns with the pps' lifestyles This is probably because these therapies help to inhibit melatonin secretion at an appropriate time (but notes: study did not look at melatonin levels)
Lewy et al (2006): SAD could be the result of an incompatibility between melatoninmediated biological instincts and lifestyle: The brain is sensitive to changes in the periods of time over which melatonin is released: as days become shorter and more melatonin is released, this provides a signal to the brain to trigger other activities e.g. some animals will enter hibernation or begin their mating season in response to changes in the length of the night. So maybe humans living at high/low latitudes are also being told by their bodies to hibernate. This hypothesis was tested using a similar design to Avery et al (2001), but with low doses of melatonin also given to one group in the evening. Sleep patterns and mood improved in this group, but not as much as in those who received bright light therapy in the morning.
IB Psychology / BLOA / Hormones and Behaviour Notes / Patricia George / November, 2012
Daan & Lewy (1984) found that if travelling eastward, then early day light exposure can help. If travelling westward, exposure to sunlight late in the day will help to lengthen your internal clock to match that of the new time zone. SAD: Early research by Rosenthal et al. (1984) has allowed Clinicians to identify and treat those people suffering with SAD. Although the exact link between melatonin and SAD is not immediately clear in all cases, because of the relationship between melatonin and darkness/light, light therapy as a therapy has become an effective alternative to drug therapy. There has also been further trials using light therapy for those suffering from MDD (Major Depressive Disorder) and for those that are moderately depressed, light therapy has been found to be as effective as drug therapy, with the benefit of reducing the normal complications/side effects of drug therapy (Terman and Terman, 2005) However, because of the contradictory findings of the role of melatonin and SAD, the exact role that hormones may plan is unclear future research may help clarify this difficulty.
IB Psychology / BLOA / Hormones and Behaviour Notes / Patricia George / November, 2012
Melatonin & SAD Reading: Lindsleys paper on Seasonal Affective Disorder (SAD): About light, depression & melatonin: http://www-pmhs.stjohns.k12.fl.us/teachers/higginj/0B0980A30118C716.49/Seasonal Affective Disorder--Melatonin.pdf Wiki on Rosenthal: http://en.wikipedia.org/wiki/Norman_E._Rosenthal Rosenthal question and answers about SAD: http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2686645/ Rosenthals original 1994 research on SAD: http://wwwpmhs.stjohns.k12.fl.us/teachers/higginj/0B0980A3-0118C716.48/SAD-originalRosenthal-report.pdf Science Daily Article (2006): Melatonin improves mood in Winter Depression: http://www.sciencedaily.com/releases/2006/05/060501113832.htm
Melatonin Video Links: SCN:
See
movie:
Howard
Hughes
Medical
Institute
(1
minute):
http://www.hhmi.org/biointeractive/clocks/animations.html
What
is
melatonin
(2
minutes):
http://www.youtube.com/watch?v=EUyBDGgsk_I&list=PLCE7203AD5E449196&index=19&feature =plpp_video
SAD:
prevalence
in
USA,
symptoms
and
therapy
(3
minutes):
http://www.youtube.com/watch?v=2XM-9- quNF4&list=PLCE7203AD5E449196&index=21&feature=plpp_video
All
accessed
November,
2012
Melatonin Extension work (also see references later): The Priory: on SAD diagnosis, symptoms, explanations for cause and therapies. http://www.priory.com/psych/SAD.htm Overview of SAD & therapy: http://www.lef.org/protocols/emotional_health/seasonal_affective_disorder_01.htm Terman and Terman (2005) Light Therapy for Seasonal and Nonseasonal Depression: Efficacy, Protocol, Safety, and Side Effects: CNS Spectrums, volume 10, number 8. http://mbldownloads.com/0805CNS_Terman_CME.pdf
IB Psychology / BLOA / Hormones and Behaviour Notes / Patricia George / November, 2012
Oxytocin
Oxytocin is one of the two major hormones that are secreted from an area of the brain called the posterior pituitary (the other one is called vasopressin, and is involved in water regulation, though it also has been known to curl the toes of male voles).
The posterior pituitary is the one further toward the back of the head. But oxytocin is not made there, it's actually made ABOVE the pituitary, in the area of the brain called the hypothalamus, and the cells within the hypothalamus extend all the way to the posterior pituitary, allowing oxytocin to be made in one place and released in another. So oxytocin is made, and when stimulated correctly, the brain releases it. Oxytocin has endocrine actions throughout the body. It plays a very big role in sexual arousal and orgasm in both sexes. In women, oxytocin is VERY important in stimulating uterine contractions prior to birth, so much so that oxytocin is given to induce labor, and drugs that antagonize (have the opposite effects of) oxytocin are used to suppress it if labor is premature. But oxytocin does not just act on the body, it also has a big impacts on the brain. Some studies have shown that oxytocin has strong effects on trust and generosity, making it an important chemical in human social interaction. In addition to these big effects, there may be roles for oxytocin in autism, in depression (particularly in females), and of course in things like social bonding. So that's a brief introduction to oxytocin. Next time we're going to discuss the specific, known roles for oxytocin in women, especially in labour and during milk let-down, and some of the social bonding aspects.
IB Psychology / BLOA / Hormones and Behaviour Notes / Patricia George / November, 2012
Orgasm
Oxytocin is actually important in sexual arousal for both men and women. During sexual arousal, oxytocin increases rapidly, with a big burst at orgasm. In fact, in women, the strength of orgasm is directly correlated with the amount of oxytocin. Oxytocin levels correlate to sexual arousal in women, as well as the amount of vaginal lubrication present. Not only that, oxytocin fluctuates along with a womans menstrual cycle, being highest in the ovulatory phase and follicular phase, and lowest in the luteal phase (The follicular phase and ovulatory phase are the preparation and release of the egg, respectively, and fertility will peak at ovulation for obvious reasons). The luteal phase is the phase after ovulation, as the egg sits around and grows old until the shedding of the uterine lining during menstruation at the end of the month. So oxytocin is very important physically, helping us enjoy the procreation of the species and allowing the species to get out of the womb and get fed. Now, we move on to the first of many fuzzier roles for oxytocin:
Maternal bonding
Oxytocin DOES influence behavior. Oxytocin promotes things like affiliative behaviour with ones young. Examples: rats, once they give birth, will pick up pups and carry them around. Theyll build a nest for them (if they havent already), and lick them and basically associate with them like good rat mommies. However, if you give a rat mom something to block oxytocin, she will not pick up the pups, carry them around, or make a nest. Giving oxytocin to sheep will induce maternal behaviour by sheep for lambs that are not their own, even if the sheep has never given birth. And this pattern appears to hold true in humans as well. Mothers who have secure attachments to their new-borns have stronger activation of the pituitary (where oxytocin is released) when they see pictures of their child, than mothers with less secure attachments. Some studies also indicate that women with particular oxytocin gene regulation may show more signs of sensitive parenting. It appears that oxytocin release is a significant part of how women react to their babies, and how much they affiliate with them in the first months of life. Controversial: And this is where people get squirmy. Because does this mean that women are the TOOLS of their HORMONES? If women are the tools of their hormones, this this mean they that BIOLOGY has DECREED that they stay indoors, barefoot and pregnant? While we could argue that women (and men) are certainly influenced by their hormones, and certainly influenced by their genes, but hormones and genes do not act in a vacuum. They act within an environment, and very importantly, within a society. A woman is very capable of both affiliating and responding sensitively to her baby and to still maintain a life. We are certainly not forced by our hormones to play certain roles. Its important to remember that societal interactions are as important, and sometimes MORE important, than hormones and genes. We are all capable of learning from our surroundings and learning what works best for our children, and it is obvious that fluctuations in oxytocin levels are not the be all end all of parenting. If they WERE, then all parents would have uniformly high oxytocin levels, evolution having weeded out over time the primate females who had low oxytocin levels, and thus did not care for their young effectively and raise successful offspring. As people with high and low oxytocin are still out there and still raising kids, you can be pretty sure there are other factors at work.
IB
Psychology
/
BLOA
/
Hormones
and
Behaviour
Notes
/
Patricia
George
/
November,
2012
In summary:
So when it comes down to it, yes, the research suggests that we are influenced by our hormones. But we are ALSO under the influence of human society and the environmental influences coming in through our vast prefrontal cortex. And to discount the incredible influences of society and the cortex would be very naive indeed.
Full reference: Damasio, A. (2005) Brain trust. Human Behaviour. Nature. Volume 435, No. 2. http://teaching.ust.hk/%7Eecon695/Damasio_on_Trust_Oxytocin_N_V.pdf
Oxytocin Reading:
Scientific American Article (2008): http://www.scientificamerican.com/article.cfm?id=totrust-or-not-to-trust
http://www.youtube.com/watch?v=rFAdlU2ETjU
Oxytocin: "Best Experimental/Animation" at the 2009 Colorado College Film Festival. (4 minutes): http://www.youtube.com/watch?v=KlUJ5ESoUw8 BBC Horizon: Are you good or evil: The chemistry of morality (video 15 minutes although only first part is applicable to our topic):
IB Psychology / BLOA / Hormones and Behaviour Notes / Patricia George / November, 2012
Baumgartner, T., Heinrichs, M., Vonlanthen, Al, Fischbacher, U., and Fehr, E. (2008) Oxytocin shapes the neural circuitry of trust and trust adaptation in humans. Neuron Volume 58, pages 639650. Full paper
available:
http://www.sciencedirect.com/science/article/pii/S0896627308003279 PDF: http://ac.elscdn.com/S0896627308003279/1-s2.0-S0896627308003279-main.pdf?_tid=f01c0900-20db-11e2-83e600000aab0f02&acdnat=1351414157_5813b16cc4e83af1cbf142dea8f0fc8b Bower, B. (2000) Chemical Spray Shows Power as Trust Booster,
http://www.flatrock.org.nz/topics/drugs/chemical_spray_builds_trust.htm from original source
sciencenews.org Science News Volume 167 Number 23 on 4 June 2005 page 356 Carey, B. (2005) Dont trust anyone? Perhaps you lack oxytocin. International Herald Tribune, from The New York Times, Friday 3rd June 2005. Available at: http://www- pmhs.stjohns.k12.fl.us/teachers/higginj/0B0980A3-0118C716.47/The%20neurobiology%20of%20Trust.pdf
Damasio, A. (2005) Brain trust. Human Behaviour. Nature. Volume 435, No. 2.
http://teaching.ust.hk/%7Eecon695/Damasio_on_Trust_Oxytocin_N_V.pdf
Kosfeld, M., Heinrichs, M., Zak, P., Fischbacher, U. & Fehr, E. 2005. Oxytocin Increases Trust in Humans. Nature. Volume 435, pages 673-676. Abstract available at: http://www.nature.com/nature/journal/v435/n7042/full/nature03701.html Full paper available: http://wwwpsych.stanford.edu/~knutson/bad/kosfeld05.pdf
Scientific American Article (2008): http://www.scientificamerican.com/article.cfm?id=to-trust-or-not-totrust
Van Ijzendoorn, M.H., Huffmeijer, R., Alink, L.R., Bakermans-Kranenburg, M.J. & Tops, M. (published online 2011) The impact o oxytocin administration on charitable donating is moderated by experiences of parental love-withdrawal. Fronteirs in Developmental Psychology. Article available at:
http://www.frontiersin.org/developmental_psychology/10.3389/fpsyg.2011.00258/full
IB Psychology / BLOA / Hormones and Behaviour Notes / Patricia George / November, 2012