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hello everyone and welcome to lesson two
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of our night aling education series My
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name is Logan and I hold a PhD in
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medical science from the Karolinska
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Institute in Stockholm Sweden where my
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PhD work was on circadian rhythms So I
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will be leading us through today's
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lesson circadian rhythm essentials as an
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overview for what we'll be talking about
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today in this lesson We'll start with
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understanding our circadian rhythm what
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the word circadian even means and how we
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can really manage our body's function
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over the course of a day We'll next move
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into an important factor for our
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circadian rhythm which is light and how
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light and timing influence our circadian
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rhythm Next we'll move into various
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hormones what time of day those hormones
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are released and what they do for our
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body And then we'll finish up with
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strategies that we can utilize to help
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us align our circadian rhythms to our
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external environment so that we can
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function more
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effectively So our first question may be
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what is a circadian rhythm and what does
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that word mean well the word circadian
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comes from two Latin words The first
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Latin word being circa which means
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around and the next Latin word being dm
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which means day So we can think of our
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circadian rhythms as the rhythmic
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function of our body around a day Now
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the circadian rhythm is a biological
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clock which is sensitive to our
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environment So our circadian rhythms
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operate by our perception of light which
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is transmitted through our eyes into our
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brain and then that transmission into
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our brain coordinates to the rest of our
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body And the area of our brain that
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receives this stimulus from our eyes is
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called the superismatic nucleus and that
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transmits information to another part of
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our brain called the hypothalamus which
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releases hormones that act on our body
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in various ways which we will talk about
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later in the lesson Now our circadian
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rhythm functions to help us regulate not
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just our sleep but also our hormones
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such as insulin which is a hormone that
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helps us get rid of sugar from our blood
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and our general hunger as well as our
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body temperature and then other
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functions such as our mood And likewise
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our circadian rhythm is sensitive to our
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external environment through other
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factors than light such as what food
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that we eat what temperature it is
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outside and even the social interactions
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that we engage in
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So our next question may be how can we
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understand circadian rhythms in the
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context of our own health well
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disruptions in our circadian rhythm
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don't just lead to issues such as sleep
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disorders We can also see that disrupted
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circadian rhythms can influence our
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health through increasing risk of
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metabolic disease and also increasing
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the risk of issues such as mood
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disorders And so this was shown in a
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study that was published with 91,000
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participants where the individuals with
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irregular 24-hour sleep wake cycles had
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an elevated level of mood disorders a
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lower overall level of happiness and
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even increased levels of feelings of
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loneliness So this really shows that
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there there's a strong interaction
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between how our body's rhythm is working
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and our general mental well-being Now
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although our circadian rhythms operate
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in a similar fashion over a 24-hour
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period it is the case that they are
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flexible to changes in our environment
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And an example of this could be jet lag
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So a jet lag change of just flying from
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a time zone that is maybe one or two
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hours or even two to four hours away can
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lead to elevated levels of feeling
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fatigued which is quite obvious to those
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of us who have experienced it but also a
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decrease in concentration and just a
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general discomfort And this is likely
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the clearest real world example of how a
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small change in our circadian rhythms
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can really influence our health So next
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here we will talk about light And light
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is important because light is the most
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essential regulator of our body's
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circadian rhythms And the way that this
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works is is light from the outside
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environment let's say the sun for
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instance is perceived by the retinas in
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our eyes And that information is then
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relayed via a nerve to the brain
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specifically the superchismatic nucleus
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which then tells the hypothalamus
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another region of our brain that
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releases hormones what time of day it is
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And this release of hormones from the
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hypothalamus then communicates this
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information to the rest of the body Now
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exposure to light in the early part of
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our waking time is not just important
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for our general feelings of energy but
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it's also important for the next time
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that we go to sleep And this has been
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shown in individuals who are shift
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workers where shift workers who are
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exposed to artificial or natural forms
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of light upon waking show a 30%
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reduction in the disturbances of sleep
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the next time that they choose to go to
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sleep And so it's not just the case that
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light is helping us feel awake It's also
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the case that exposure to light early
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upon waking is helping us sleep the next
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time that we go to sleep Now on the flip
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side of this coin it's also the case
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that exposure to light too close to
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going to sleep can influence our ability
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to sleep And the reason that this
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happens is this artificial light let's
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say from our screens or from our
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televisions is perceived by the eyes and
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the superchismatic nucleus as being
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daytime And what this causes is a
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reduction in the release of a hormone
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called melatonin which is responsible
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for a drop in body temperature and a
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general preparedness for sleep And this
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reduction in melatonin will make us feel
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less sleepy and as a result can
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influence our ability to fall asleep So
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it's quite important to manage our
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exposure to light for our general
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circadian rhythms and our well-being
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And so to continue on a bit with how
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important timing is for managing our
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circadian rhythm it's important to
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remember that our circadian clock
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controls these key functions such as our
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hormone release and our metabolism and
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that we can modulate specific external
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factors so that we can optimize our
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general rhythms Now it's known in the
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scientific data that people who work
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shift work are more prone to issues such
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as circadian disruption and also risk of
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cardiovascular disease and diabetes And
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there are fundamental reasons for this
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One of those fundamental reasons is that
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individuals who work shift work often
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eat at irregular times They're not
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typically eating the standard breakfast
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that non-shift workers eat when they
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immediately wake up and they're just
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eating less often with other people And
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so one way to counteract this would be
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to eat meals at a specific time every
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day always And so an example of this
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would be perhaps we work a shift from uh
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11:00 p.m until 7 a.m and we let's say
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wake up at something like 5:00 p.m So if
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we wake up at 5:00 p.m and we eat a meal
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at 6:00 p.m and then eat another meal
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three to four hours later and then
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another meal three to four hours later
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We should be doing that consistently
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every day even on days where we're not
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working so that our body can anticipate
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this in terms of their rhythm and we can
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prepare digestive enzymes and all the
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other bodily processes that are
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associated with digesting our food
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Additionally it's important as well to
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go to sleep at the same time every day
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And the reason for this is so that our
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body can anticipate the release of
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specific sleep hormones such as
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melatonin to prepare us for sleep in a
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coordinated way repetitively over time
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And if we can implement these tips of
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consistency in both our eating and our
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sleeping time regimen then this can help
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us coordinate and really overcome any
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sort of challenges that are involved
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with working shift work So now we'll
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move into talking a bit about hormones
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And as I mentioned hormones are
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oscillating over the course of a day in
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ways to help us maintain our function
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and optimize our function during either
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the early part of the day or the later
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part of the day And there are a few
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examples of this One primary example is
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cortisol You may have heard of cortisol
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before This is associated with being the
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stress hormone which we associate with
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being a bad thing typically But actually
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uh cortisol is a hormone that helps us
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feel more awake and alert And it's the
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case in the scientific research that
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individuals who have higher levels of
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morning cortisol perform about 20%
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better on memory and attention tasks So
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this hormone is helping individuals
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retain memory and feel alert Another
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example of a hormone that changes over
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the course of the day is melatonin I'd
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mentioned this in previous slides but
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melatonin helps our body to prepare for
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sleep And part of the way it does this
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is by reducing our body temperature
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which prepares us for deeper phases of
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sleep such as phase three and phase 4
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sleep And speaking of phase three and
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phase four sleep this moves us to growth
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hormone And growth hormone is a hormone
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that is associated with repair of our
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body's tissues such as our muscle And
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it's a recovery hormone that can help us
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recover from exercise or our daily
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activities and it is elevated actually
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during phase three and phase four sleep
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So this is another reason why it's
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important to maintain a steady
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biological rhythm so we can reach these
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deeper stages of sleep which can help us
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recover from our daily
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activities Continuing forward here with
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just a few more hormones Our next
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hormone that we'll talk about is insulin
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So insulin is typically associated with
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diabetes However it is a helpful hormone
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for our general energy metabolism What
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insulin does is is it takes sugar from
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our bloodstream and deposits it into our
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cells to be used for energy And insulin
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is at its most elevated earlier upon
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waking And so if we're consuming foods
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such as breads or cereals those foods
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are more digested and then placed into
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our cells more readily by insulin
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earlier upon
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waking The next hormone here that we'll
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talk about is testosterone So like
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insulin testosterone is elevated in the
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earlier part of our day and it is
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responsible in both males and in females
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for greater levels of energy
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improvements in libido and greater
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muscle strength So we can capitalize
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upon these benefits earlier upon waking
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through
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testosterone And our last hormone here
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is thyroid hormone So thyroid hormone is
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responsible for cellular energy
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metabolism and energy generally in the
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cells in our body And thyroid hormone is
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increased later after waking So as we
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approach sleep thyroid hormone is our
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general means of energy
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production So as a general takeaway here
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after talking about all these hormones
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the circadian rhythms generally help us
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manage these hormones in a tightly
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regulated process so that we can
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function more as we move throughout our
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day So as a final takeaway here we'll
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just move into a summary of what we've
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learned today Our circadian rhythms are
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an integral part of our general
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functioning in our body and they are
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sensitive to light So the perception of
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light in our environment coordinates
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information to our eyes which then
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coordinates to our brain which
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coordinates to the rest of our body so
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that our body knows what time it is And
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what this does is it oscillates our
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release of various hormones that help us
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manage our energy levels Now there are
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tips to help maintain our circadian
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function whether we're night owls or
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early birds One of these tips is to just
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maintain a consistent sleep schedule And
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this can be done by just coordinating
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what time we go to bed and what time we
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wake up every day even on days when
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we're not working And this helps our
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brain to know when to release hormones
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like melatonin so that we can more
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effectively prepare for sleep The next
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tip here is just coordinating and making
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sure that we're eating our meals at
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consistent times every day so that our
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digestive hormones can know when to be
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released to help us more effectively
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deposit the food that we're eating into
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our cells and utilize them for energy
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The next tip here is to get natural
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light exposure as early as possible upon
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waking so that we can get the release of
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those helpful hormones such as cortisol
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to help us feel more alert and to have
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an improvement in our memory and
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cognitive function And then our last tip
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here is to avoid uh exposure to
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artificial light as we reach our time to
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sleep And the reason for this is because
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as we prepare for our time to sleep we
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see the release of melatonin And if our
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eyes are perceiving light then our brain
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thinks that it is daytime and that will
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impair the release of melatonin which
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can impair our ability to sleep And so
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if we can remember these tips we can
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more tightly coordinate our circadian
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rhythms and function better and be more
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energetic as we move throughout our day
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And so that is all I have for today I
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will see you at our next lesson Thank
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you for listening to Night Owl