Infradian Rhythms
Summary
TLDRThis lesson delves into infradian rhythms, specifically focusing on the menstrual cycle and Seasonal Affective Disorder (SAD). It explains how internal factors like hormones and external influences such as pheromones and light affect these cycles. The role of synchronization in the menstrual cycle is discussed, along with the evolutionary benefits and potential confounding factors. SAD is linked to melatonin overproduction and light exposure, with phototherapy suggested as a treatment. The lesson highlights the complexity of biological rhythms and their interaction with both internal and external factors.
Takeaways
- π The lesson focuses on infradian rhythms, which are biological rhythms longer than a day, including the menstrual cycle and Seasonal Affective Disorder (SAD).
- π Infradain rhythms are distinguished from circadian and ultradian rhythms by their less frequent periodic cycles.
- π¬ The menstrual cycle is controlled by hormones like estrogen and progesterone, which are internal factors, and can be influenced by external factors such as synchronization with other women's cycles.
- π‘οΈ Synchronization of the menstrual cycle can be influenced by pheromones, chemical signals released into the environment that can affect others' internal mechanisms.
- 𧬠Martha McClintock's study showed a correlation between close living conditions and menstrual cycle synchronization among women in an all-female dormitory.
- π€ The role of pheromones as internal or external factors in biological rhythms is a point of analysis, given their release into the environment but biological origin.
- π°οΈ A study involving a woman in a cave without natural light showed that the absence of light can affect the menstrual cycle, indicating light as an exogenous factor.
- π The evolutionary value of menstrual cycle synchronization may include shared childcare and fair competition for mates, though this idea is debated.
- π¨οΈ Seasonal Affective Disorder is a type of depression with symptoms like low energy and social withdrawal, linked to reduced daylight during winter.
- π Endogenous factors in SAD include overproduction of melatonin and underproduction of serotonin, while exogenous factors are the absence of light.
- β¨ Phototherapy, or light exposure, has been effective in treating SAD, suggesting a strong link between light and the disorder's symptoms.
Q & A
What are infradian rhythms in the context of biopsychology?
-Infradian rhythms are biological rhythms that occur over a period longer than a day, as opposed to circadian and ultradian rhythms which have more frequent cycles.
What is an example of an infradian rhythm mentioned in the script?
-The menstrual cycle is given as an example of an infradian rhythm in the script.
What is Seasonal Affective Disorder (SAD)?
-Seasonal Affective Disorder is a type of depression that occurs during the winter months, characterized by symptoms such as low energy, hypersomnia, weight gain, and social withdrawal.
How do infradian rhythms differ from circadian and ultradian rhythms?
-Infradian rhythms have a less frequent regularity compared to circadian rhythms, which include the sleep-wake cycle and hormonal fluctuations, and ultradian rhythms, which include stages of sleep like REM and non-REM sleep.
What role do estrogen and progesterone play in the menstrual cycle?
-Estrogen causes the ovary to develop an egg which is released during ovulation, while progesterone helps the womb lining to thicken in preparation for pregnancy. If the egg isn't fertilized, the lining is disposed of, resulting in the menstrual cycle.
What is synchronization in the context of the menstrual cycle?
-Synchronization refers to the phenomenon where being around other people on their menstrual cycle can influence one's own menstrual cycle, possibly due to the influence of pheromones.
What is the evolutionary value of menstrual cycle synchronization according to the script?
-The evolutionary value of synchronization could be that if women menstruate and ovulate at the same time, it increases the likelihood of them getting pregnant simultaneously, which might be beneficial for sharing the care of babies in a group or tribe setting.
What is phototherapy and how is it related to Seasonal Affective Disorder?
-Phototherapy is the use of light exposure as a treatment for conditions like Seasonal Affective Disorder. It is based on the idea that the symptoms of SAD are related to the reduced light levels during winter months.
What are the potential confounding variables in the study of Seasonal Affective Disorder?
-Potential confounding variables include increased bills for artificial light and heating, the psychological impact of Christmas and the holiday season, and lifestyle changes such as reduced outdoor activity due to cold and darkness.
Why might not everyone exposed to reduced daylight develop Seasonal Affective Disorder?
-Not everyone develops Seasonal Affective Disorder because there may be genetic predispositions and underlying mental health issues that make some individuals more susceptible to the condition than others.
How does the study of pheromones relate to the synchronization of the menstrual cycle?
-The study of pheromones is relevant to menstrual cycle synchronization because these chemical signals, released into the environment, can influence the internal mechanisms of others, potentially affecting their menstrual cycles.
Outlines
π Infra-Daily Rhythms and Menstrual Cycle
This paragraph introduces the topic of infradian rhythms from the AQA syllabus for biopsychology, focusing on biological rhythms that exceed a day in duration, such as the menstrual cycle. It explains the distinction between infradian, circadian, and ultradian rhythms, and suggests a strategy for answering extended questions on this topic. The menstrual cycle is explored in terms of its endogenous factors, like estrogen and progesterone, and exogenous factors, such as social synchronization influenced by pheromones. The paragraph also touches on the evaluation of these rhythms, including the role of internal validity in research methods.
π Synchronization and Seasonal Affective Disorder
This section delves into the concept of synchronization of biological rhythms, particularly the menstrual cycle, and its potential evolutionary value. It discusses the possibility of women menstruating and ovulating in sync to increase the chances of pregnancy and the sharing of childcare within a group. However, it also presents counterarguments to this theory. The role of pheromones in synchronization is supported by a study involving cotton wool pads soaked in sweat, which influenced the menstrual cycles of other participants. The paragraph also introduces Seasonal Affective Disorder (SAD), a type of depression occurring in winter due to low light levels, and its symptoms like low energy and social withdrawal. The endogenous factors of SAD are the overproduction of melatonin and the underproduction of serotonin, while the exogenous factor is the lack of light.
π‘οΈ Seasonal Affective Disorder and Light Therapy
The final paragraph discusses Seasonal Affective Disorder in more depth, focusing on the hormonal imbalances caused by increased melatonin production during winter months, which may lead to a decrease in serotonin and other hormones affecting mood and appetite. Empirical evidence supporting the link between high melatonin levels and SAD is presented, along with the effectiveness of phototherapy in treating the disorder. The paragraph also considers the role of confounding variables such as increased bills, the festive season's impact on loneliness, and reduced outdoor activity during winter, which may contribute to SAD. It concludes by noting that not everyone exposed to winter conditions develops SAD, suggesting a genetic predisposition and other mental health factors that may influence its development.
Mindmap
Keywords
π‘Biological Rhythms
π‘Infradian Rhythms
π‘Menstrual Cycle
π‘Seasonal Affective Disorder (SAD)
π‘Circadian Rhythms
π‘Ultradian Rhythms
π‘Estrogen and Progesterone
π‘Synchronization
π‘Pheromones
π‘Evolutionary Value
π‘Phototherapy
Highlights
Biological rhythms are periodic cycles that occur regularly, with infradian rhythms taking longer than a day, such as the menstrual cycle.
Infradian rhythms are distinguished from circadian and ultradian rhythms by their less frequent regularity.
The menstrual cycle is controlled mainly by hormones estrogen and progesterone, which are endogenous factors.
Synchronization of the menstrual cycle can be influenced by external factors such as pheromones from other women.
Martha McClintock's study found a correlation between exposure to other women and menstrual cycle synchronization.
Pheromones, released through sweat and body odor, can send signals that influence others' internal mechanisms.
The role of pheromones in synchronization raises questions about whether they are considered internal or external factors.
Isolation studies show that the absence of natural light can shorten the menstrual cycle, indicating light as an exogenous factor.
Synchronization of menstrual cycles may have evolutionary value, such as shared care of babies and fair competition for mates.
Shanks argues against the idea that competition is the basis of synchronization, suggesting women tend to 'tend and befriend' rather than compete.
A study involving cotton wool and pheromones found synchronization effects, supporting the role of pheromones in cycle synchronization.
Mathematical chances suggest that women may naturally synchronize menstrual cycles over several cycles, independent of pheromones.
Seasonal Affective Disorder (SAD) is a type of depression with symptoms similar to regular depression but occurring only in winter months.
SAD is linked to low light levels during winter, affecting melatonin and serotonin production.
Phototherapy, or light exposure, has been effective in treating SAD, suggesting the importance of light as an exogenous factor.
Not everyone exposed to reduced daylight develops SAD, indicating a possible genetic predisposition or other underlying factors.
Confounding variables such as higher bills, holiday stress, and reduced outdoor activity may exacerbate winter depression but are difficult to study in isolation.
Transcripts
so this is another lesson for
biopsychology from the AQA syllabus
psychology paper 2 uh we're looking at
biological rhythms today and we're going
to specifically focus on infradian
rhythms just a reminder infradian
rhythms are biological rhythms that take
longer than a day and an example here in
the glossery is the menstrual cycle
we'll also be looking at Seasonal
effective disorder as all other
biological rhythms they're periodic
cycles that happen regularly only that
the regularity of these ones is less
frequent than Cadian and ultradian
rhythms so just a reminder for Cadian
rhythms you can look at for example the
sleep wake cycle body temperature and
hormonal
fluctuations uh for ultradian rhythms
you will look at stages of sleep
specifically the distinction between RM
and nonm sleep
and for even Fran rhythms we will look
at today the menstrual cycle and
seasonal effect of
disorder we will start by looking at the
menstrual cycle ao1 and then the
menstrual cycle AO3 and then the do the
same sequence for the Seasonal effective
disorder this is also a good strategy
should you get an extended question on
infradian rhythms you might want to
split it into a1's for menstrual cycle
a3s for menstrual cycle and then then
again for seasonal effectory
Disorder so you might not see this but
as for cadium rhythms you can organize
your ao1 into the role of endogenous
pacemakers and exogenous zeit gers so
you will look to what extent the
menstrual cycle is dictated by internal
factors such as um estrogen and
progesterone and to what extent it's
determined by external factors and we
will see that in this case the external
Factor are other women other people on a
cycle so
synchronization and link to that the
role of pheromones and then when we look
at evaluation remember evaluation AO3 is
evaluation and Analysis so you can
analyze uh synchronization for example
as having evolutionary value you can
also uh look at the methods that are
used to research um the menstrual cycle
and to what extent they have internal
validity and to what extent they have
issues so uh as you might already know
the menstrual cycle is controlled mainly
by the hormones estrogen and pro
progesterone so these are the indous
factors that determine a menstrual cycle
you would want to go into a bit more
detail and say that estrogen causes the
ovary to develop an egg it's uh released
and this is called ovulation and then
progesterone helps the womb lining to
grow thicker ready for pregnancy but if
uh the egg isn't fertilized then it's
disposed so the menstrual cycle is the
result of this
disposal now external factors here are
synchronization it means that being
around other people on their menstrual
cycle uh can
change the cycle of One's Own menstrual
cycle uh Martha mlin Tuk studied this
looking at women that lived in all
female univers dorms and found that
there was a strong positive correlation
between how long people were exposed to
each other so spent time together and
how closely they experienced their
menstrual
cycle so this emphasizes the role of
pheromones pheromones are like our
hormones but released into the outside
world through our sweat our body smell
our skin basically our skin conduct
these pheromones that s send signals to
others about our internal mechanisms and
therefore uh might influence their
internal mechanism so there's definitely
a question here for Ure fre as to where
pheromones are considered internal or
external because they're released into
the outside world so other people's
pheromone can influence us but then
again they're a biological factor so
that's a good an analysis
point and as I said there's uh in terms
of exogenous Z gabes there's isolation
studies like in the Cadian rhythms you
remember cifra so here we've got another
study but this time it's a woman who
spent three months in a cave with uh no
natural light and it was found that her
menstrual cycle shortened and this shows
that light is also an exogenous factor
that might be implicated in the
menstrual cycle so not only pheromones
and exposure to other individuals but
also the presence of our absence of the
light seems to synchronize not only the
sleep wake
cycle so moving on to
AO3 uh we can talk about the
evolutionary value of synchronization if
women are uh menstrating at the same
time they're also ovulating at the same
time meaning there's a highly higher
likelihood of them uh getting pregnant
at the same time and therefore the
children being born at the same time so
if living in a in a group in a tribe
that might make it uh more effective in
terms of sharing uh the care of babies
lactating at the same time Etc also
competition for males is fairer if all
women are either fertile or not fertile
in
sync there are arguments against this as
you can see Shanks argues that it's not
really true that uh for women
competition promotes survival women are
more kind of tend and befriend rather
than fight or flight um spe genders and
therefore the idea that uh that
competition is at the basis of
synchronization doesn't really have a
sound sound
basis there's also research to support
uh
synchronization uh this is a slightly
disgusting stud study where participants
Place coton wool uh under their armpits
without deodorant so the coton W was
impregnated with the sweat and then that
was swiped on the upper Li lip of
another participant and that was to
expose that participant to the
pheromones of uh of the sweating
participant and they did find that uh
through smelling the pheromones of U of
the other participants the ones uh
exposed to the pheromones did seem to
synchronize or that there get closer to
the kind of the donors of the pheromones
so this is supporting evidence in a kind
of standardized control
um study Beyond just looking at young
people that spent time together in dorms
that is yeah more naturalistic more with
high ecological validity but not with a
high control of other extraneous
variables so this seems to substantiate
the role of pheromones in
synchronization now generally speaking
there are the questions about
synchronization the first one is that
mathematically we're women are bound to
synchronize at some po point in the
course of three or four Cycles
especially because the length of stud of
um Cycles is not the same for everyone
so it's based on the flawed assumption
that everybody's cycle is 28 days for
example so there are kind of
mathematical reasons where by
synchronization could happen just by
chance rather than because of exposure
to
pheromones we're Mo moving on now to the
second infradian Rhythm so we're going
to look at the AO ons for Seasonal
effective disorder first of all Seasonal
effective disorder is a specific type of
depression that is similar to depression
in terms of its symptoms however it only
occurs during the winter months and this
seems to be attributed to uh the low
levels of light uh the symptoms include
low energy hypersomnia that means
sleeping too much overing weight gain
and social withdrawal so spending a lot
of time alone at home either sleeping or
eating this is what it
suggests now
for Seasonal effective disorder the
endogenous pacemakers that are involved
are um the prod the over production of
melatonin that results in the
underproduction of Serotonin and the
exogenous light Gaber is the absence of
light and therefore in the winter months
we know that the days are shorter in
terms of A3 we don't have a lot we have
phototherapy that is PR practical
application of our knowledge into the
reasons why sad might um occur and how
we can treat
it so melatonin uh is a hormone the
endocrine system is the system of glands
that secrete hormones so if there's an
over production of melatonin there will
be a strain in the pineal gland that
might result in an underproduction of
other hormones within the endocrine
system in this case the hormones that
might be influenced are um the thyroid
hormone serotonin and adrenaline so it
makes sense to think that if you're
producing loads of melatonin because
it's nearly always dark then you will be
producing less of that mood regulating
hormone serotonin uh T the thyroid
meaning that you might feel hungry when
you don't need food and the lack of
adrenaline might not motivate you to go
out so it does link to all of the
symptoms that we described
[Music]
earlier sad patients have consistently
higher daytime melatonin levels so there
is empirical evidence that Seasonal
effective disorder does seem to be
linked to a higher melatonin level so
there is a maybe a hypers sensitivity to
uh light and darkness in these
individuals and that is linked to all
the symptoms that we
described uh light is obviously the
exogenous s game involved here in Winter
we know that the daytime hours reduce
significantly maybe to maybe five or 6
hours a day of natural light if you
consider also people maybe having a 9
to5 job it means that they will
potentially never be exposed to natural
light in the winter
months so for A3 we can look at the
evidence that uh light is implicated in
uh in Seasonal effective disorder
because phototherapy that means light
exposure is effective yeah uh here we've
got Eastman treated uh Seasonal
effective disorder patients with bright
light or a placebo and they found that
those treated with the real light rather
than the placebo were more likely to
respond uh and sometimes they had a full
remission of symptoms meaning they
weren't clinically that depressed
anymore however 60% uh of sufferers um
found a reduction after treatment but
30% seem to improve after a placebo so
there's the question as to whether light
or other factors psychological factors
rather than uh exogenous light gers are
also involved in Seasonal effective
disorder for example in the winter
months uh our bills will be higher
because we have to use more artificial
light so our electric bills will be
higher our gas bills will be higher
because we have to keep the heating on
in the winter months we have Christmas
that although it's very festive for some
people it's qu could be very depressing
especially if they don't have close
friends or family to spend it with it
might make them feel very lonely and
also lifestyle in the winter you're less
likely to go out you're less likely to
go out for a walk because it's cold
because it's dark so those might also be
factors that um exacerbate people's low
mood these are all confounding variables
because they go along with the winter
months we can't separate them and study
them so they're not extraneous variables
that we could control for they're
confounding that do impact on what we're
researching and there's basically
nothing we can do about
that lastly another factor that has to
be noted is that not everyone exposed to
reduced daylight develops Seasonal
effective disorder because everybody is
experiencing winter months and but not
everybody is falling into depression so
that means that there are genetic
predisposition uh overall uh issues with
mental health that make it more likely
for some people than other to develop
Seasonal effective disorder therefore uh
questioning the extent to which it is a
matter of exogenous and endogenous
factors and whether it's something
completely separate
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