What is stressing you out?
Stress is definitely something all of us deal with it in varying degrees throughout our
lives, but what stresses the human body out more than anything and more importantly, how
does the body physiologically deal with that stress?
So, in today's video, we'll of course utilize the good average to go over some of the relevant
anatomy involved in the stress response as well as discuss the amazing physiological
changes that occur and are there ever any situations where the stress response could
be taken too far and lead to potential long-term health consequences?
It's going to be a fun, non-stressful video.
So, of course, let's jump right into this anatomical awesomeness.
[Intro]
So, before we take a look at some of these amazing cadaver dissections and structures
that are related to stress, let's first talk about what actually stresses us out and if
you were to take a look at say like a top 10 list of most stressful life events, two
things almost always hit the top of the list.
One is death of a loved one, two - divorce or other relationship issues.
Now, those top two probably don't surprise you but the rest of the list is composed of
things like moving, major injury or illness, losing a job, or even getting a new job, getting
married, problems at work or school, financial instability, retirement, and even transitioning
into adulthood.
Now, what's interesting about this list is that a lot of those stressors have a future
component or in other words, often times, we stress or our stress is tied to some possible
future event - What happens if I can't pay my bills?
What happens if I lose my job?
I only have two weeks to move.
This is quite the different list than you might see chiseled on the wall of our early
human ancestors that we affectionately to call cavemen and cave women but, do you think
that our early human ancestors were really stressed in the same way like about finances
work or even planning that perfect wedding?
No.
Their stresses were very similar to say like other animals and were centered really around
the here and the now and the necessities of survival.
So, how your body responds physiologically to stress evolved and developed to deal with
some of these more primitive stresses or stimuli that we don't experience in the exact same
way as our early human ancestors.
Don't get me wrong, I'm not trying to diminish the stress that we experience today.
I mention this because that many times a perceived stress regardless if happened thousands of
years ago or today is still a perceived stress of the human body and even though you can
be consciously aware that the stresses we experience are going to have some differences
from the stresses that early human ancestors experienced, our physiological stress response
system is still going to behave in a very similar way.
So, what happens physiologically when the human body gets stressed?
We're going to talk about two main responses.
One, activation of the sympathetic nervous system also known as the fight or flight response
and two, release of a hormone called Cortisol, which is often nicknamed the stress hormone.
So, let's start with that sympathetic response.
Let's say you get scared or injured or maybe you've got this really big test that you're
nervous about.
That sensory information or those signals like the pain, visual, or auditory stimuli
and even the thoughts surrounding that perceived stress will get processed in various regions
throughout the, but much of that info will eventually get relayed to the center of the
brain in a structure that you can see here called the hypothalamus and the hypothalamus
helps to regulate and control the sympathetic nervous system.
The hypothalamus will then activate sympathetic neurons called Preganglionic Neurons that
are found in the spinal cord from T1 to L2 sometimes even in the L3.
So you can see these preganglionic neurons are found originating in multiple spinal levels
throughout the cord and this allows them to get the signal out, synapse with another sympathetic
neuron called the Post Ganglionic Neuron and these post ganglionic neurons can now get
that signal to multiple regions and target organs throughout the body where they will
release a neurotransmitter called Norepinephrine also known as Noradrenaline.
Now, I do realize I probably could have just said the hypothalamus activates a sympathetic
nervous system which causes norepinephrine to be released on multiple organs but then
you'd miss out on the opportunity to discuss pre-ganglionic neurons synapsing with post
ganglionic neurons with your friends at dinner on Friday night.
So, what happens once this norepinephrine is released and binds to the receptors on
these target organs?
Well, we'll see things like increases in heart rate and the heart itself will contract more
forcefully.
We'll also see that the blood pressure will go up.
The airways within the lung tissue will open up - what we call bronchodilation which will
allow for more air in and out of the lungs.
We'll also see that blood vessels supplying certain organs and structures that are necessary
during exercise or fending off dangerous situations will vasodilate or open up thereby increasing
blood flow to things like muscle tissue, the heart itself and even the liver - whereas
organs like the digestive tract or the kidneys, we're going to see that those blood vessels
will vasoconstrict because we're not terribly concerned about digesting food or producing
urine during a fight or flight response.
We'll also see that the liver will release more glucose increasing blood sugar levels
so we have more access to energy stores and also the pupils will dilate as well as activation
of sweat glands.
One last really cool thing that happens is that the sympathetic nervous system will also
activate the adrenal gland, specifically the center of the gland called the Adrenal Medulla
and the adrenal medulla will release epinephrine, also known as adrenaline and even more norepinephrine
that we talked about earlier.
So then the adrenal gland will just bolster and support the sympathetic response that's
already being initiated by the nervous system.
Now, pretty much all of us have experienced this stress response at some level.
And we all have a pretty good idea that these changes caused by the sympathetic nervous
system occur almost instantaneously and generally, we want these fight-or-flight responses and
even the increase of cortisol that we're going to talk about soon to be short lived.
Activate, help us deal with the stress and then go back down to normal levels.
Unfortunately, this doesn't always occur.
Sometimes, we carry the worry with us.
We continue to worry about some possible event or some other stressor in our life and we
prolong that stress response.
This can be linked to things like anxiety, panic, and even depression and these mental
health concerns are no joke.
They can definitely affect a person's day-to-day life and day-to-day activities and that's
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So, back to another part of the stress response, cortisol.
cortisol again is often nicknamed the stress hormone because yes, it is release during
the stress response but sometimes I think cortisol gets a little bit of a bad rap and
that's because often people will hear that increased cortisol levels can lead to potential
long-term health complications but there's a bit more to it than that.
Yes, prolonged increased levels of cortisol can be associated with certain health conditions,
things like cushing syndrome but you can also have too little of cortisol like what happens
in Addison's disease which is actually a condition that JFK had.
In fact, a person could die if their body stopped producing cortisol altogether.
So, you can see, we do need certain levels of cortisol but cortisol is like any of the
other hormones.
I often tell my students, with hormones, you don't want too little, you don't want too
much, you want just the right amount in that proper range.
So, after this little soap box, what does cortisol actually do during the stress response?
So, this takes us back to the hypothalamus.
Remember, we mentioned earlier that the hypothalamus was receiving information about stress and
activated the sympathetic nervous system.
The hypothalamus will also control the release of cortisol and how it does this is that the
hypothalamus will release a substance called Corticotropin Releasing Hormone and that corticotropin
releasing hormone will diffuse into tiny little blood vessels in this area that you can't
see and those blood vessels will deliver that corticotropin releasing hormone directly to
the anterior pituitary gland and it tells the cells in the anterior pituitary to release
another hormone called Adrenal Corticotropic Hormone or ACTH.
I realize that's a mouthful but in a minute that long name will make sense.
Once the anterior pituitary releases that ACTH into the bloodstream, that ACTH will
circulate throughout the body but it will only bind to ACTH receptors and those receptors
are going to be found in the adrenal gland, specifically the outer portion of the adrenal
gland called the Adrenal Cortex.
It tells the cells in the adrenal cortex to release cortisol.
Now, I realize that I probably could have just said - hypothalamus tells the anterior
pituitary to tell the adrenal cortex to release cortisol but where would the fun in that be?
Details are cool, right Jeffrey?
He said yes.
And finally, what does the cortisol actually do once it's released into the bloodstream?
Cortisol has some powerful metabolic effects on the macronutrients - the carbohydrates,
proteins, and fats.
It causes the liver to increase the rate of Gluconeogenesis which is taking a non-carbohydrate
substance such as a protein and converting it into the carbohydrate glucose.
This cortisol will cause the liver to increase this rate of gluconeogenesis by six to 10
fold.
Cortisol also inhibits or antagonizes the effects of insulin.
Insulin essentially tells your cells to bring in glucose or the sugar from the bloodstream
therefore lowering blood sugar levels.
So, if cortisol is antagonizing or inhibiting that effect, glucose or blood sugar levels
remain high where that glucose can be ready and available.
It's effect on protein metabolism is that there's going to be a reduction in protein
synthesis and mobilization of amino acids.
Amino acids being the building blocks of proteins.
So, essentially it's going to pull those amino acids from tissues like skeletal muscle so
that those amino acids could be ready and available for things like gluconeogenesis.
It's effect on fat metabolism is mobilization of fatty acids from the adipose tissue.
So, now those fats or fatty acids can be utilized for energy which will help conserve the glucose
and the glycogen.
Glycogen just being the storage form of glucose.
That was a lot.
So you might be wondering how do these changes created by cortisol relate to stress.
Well, as you can see, we've essentially increased availability of energy by creating more glucose
and mobilizing fatty acids or fats that could also be utilized for energy and when we're
talking about the stress or fight or flight response, our body is in a situation where
it's systems and cells are going to need more energy available in order to deal with that
stressful situation.
And if that stressful situation includes trauma or injury, tissue damage and/or infection
the mobilization of those fats and amino acids could be utilized by those damaged or stress
cells for repair and even the conversion to other substances that are essential for the
life of the cell.
Some have even wondered and theorized if this mobilization of fats, amino acids, and the
increase of glucose was partly evolved due to something that really stresses out the
body which our early ancestors probably dealt with much more than we did and that is starvation.
And in the context of starvation, mobilizing all these macronutrients and increasing energy
availability kind of make sense.
But what about inflammation?
Cortisol actually helps to reduce inflammation.
Cortisol can help block the early stages of inflammation as well as help to resolve inflammation
that is already been established and that's why we'll sometimes use anti-inflammatory
steroids in certain situations that will mimic the effects of this steroid hormone, cortisol,
and that can help people with certain inflammatory conditions.
Now, again, these fighter or stress responses, we want them to be short lived - activate,
help the body do with the stress go back down to normal levels but if these cortisol levels
are chronically elevated and the sympathetic nervous system is constantly being ramped
up or firing off like crazy, this can potentially lead to and is linked to potential long-term
health consequences.
Things like cardiovascular effects, increased blood pressure, increased risk of heart attack
and stroke, weight gain, and redistribution of body fat, glucose intolerance because remember,
cortisol would inhibit or antagonize the effects of insulin.
Potentials for muscle weakness as we were mobilizing those amino acids pulling them
from things like muscle tissue.
You also see an increase risk of infection because if the cortisol is over-suppressing
inflammation, that can be a problem because again, inflammation is kind of sharing that
Goldilocks principle that we talked about with the hormones - you don't want too much
inflammation and you also don't want too little inflammation where you can't fight off basic
infections.
You want just the right amount or the proper intensity of the inflammatory response.
And finally let's wrap all this up.
And I know I sound like a little bit of a broken record but again, these stress responses
in the acute phase or in a short lived situation are good, they're necessary, they help us
deal with the stress responses but again, if they're prolonged, that's when we run into
issues and I do think it's interesting to compare the stresses of our early ancestors
compared to say like us.
It doesn't mean we didn't share anything in common.
It's not like our early ancestors have mental and emotional stress.
It's not like they didn't care that people died or couldn't potentially have relationship
issues but in general, they dealt with more physical stresses than we did and in a way
it's kind of shifted in a way that we have less physical stresses that we deal with in
general and more mental stresses and the interesting thing about mental and emotional versus physical
stresses is if somebody's running from a predator, that stress comes up high, they run away,
they get to safety, and that stress response comes down whereas mental and emotional stresses,
not always but often times have an increase likelihood of being perpetuated - perpetuating
in our mind and being longer lasting.
So, I do think it's a very important for us to frolic around and do something that makes
you happy and reduces your stress each day like learning about the human body is awesome
so of course that's going to reduce stress.
You can also do things like leave positive comments, positive likes that's bound to perpetuate
positivity and decrease stress and conveniently, you can do that below.
I know that was a little bit shameless but in all seriousness, if you do find yourself
with a high amount of stress, anxiety, panic attacks or even depression, please do not
hesitate to talk to somebody from a clinical perspective.
When I've sent patients to a good therapist, often times they improve and have a lot of
success in those situations.
So, again, don't hesitate to talk to somebody.
We have that link below, BetterHelp, that can get you link to a therapist and of course,
thanks for watching and we'll see you in the next video.