And we've all experienced stress before, sometimes on
a daily or even hourly basis. Much like anger or joy,
stress can slowly build and simmer, or it can
strike suddenly and with great intensity.
And yeah, stress, certainly the chronic or extreme type
can be bad for your health, but defining stress
is trickier than you might think.
Psychologists would define stress as the process by
which we perceive and respond to certain events, or
stressors, that we view as challenging or threatening.
In other words, stress isn't technically an emotion, it's
more of a reaction to a disturbing or disruptive stimulus.
And our reactions stem in part from our appraisal of that
stimulus. A person can either roll with, or get worked up
about a missed flight, an increased workload, or a
strange thump in the house. These external stressors
typically fall into three main categories: catastrophes, or
unpredictable large scale events like war, natural
disasters and terrorist attacks; significant life changes,
things like moving, having a child, losing or getting a
job, or the death of a loved on; and then just everyday
inconveniences like getting caught in traffic, running
late, or feuding with your roommates.
Any of these stressful events, big or small, even the
good things, can fire up your sympathetic nervous
system and trigger that old fight or flight response.
In this way, it's important to understand that stress
is ultimately natural. You experience it for a reason
and a bit of short-lived stress can actually be a good
thing. It can make you active and alert when you need to
be, like an upcoming chemistry test might be stressing
you out, but that might help you find focus so you can
dominate that thing. And in your body, moderate stress
can kick the immune system into action to do things
like heal wounds, and fight infections. It does this by
triggering the release of stress hormones like
adrenaline and cortisol. These chemical messengers
are what get your organ systems to respond the way
you need them to when you're getting charged by a
bear, or focusing really hard on the gas law
for your chemistry test. But to also why chronic stress
Chronic Stress & the Autonomic Nervous System
can really wreck a body and mind, research has shown
that abused children have a high risk of chronic disease
and people suffering from post-traumatic stress disorder,
PTSD, which we'll talk about in an upcoming episode,
experience higher rates of digestive, respiratory,
circulatory, and infectious diseases. A lot of these
negative connections between your body's systems
have to do with the fact that many of its most basic
functions, like blood pressure, breathing, body
temperature, digestion, and heartbeat, are in part
regulated by the autonomic nervous system.
We've talked before about how the sympathetic side
of that system cranks you up, and the parasympathetic
arm calms you down, but both those systems also
interact with the so-called "brain-in-the-gut", the enteric
nervous system, which helps regulate gastrointestional
functioning. And it's this brain-gut connection that
explains how stress causes digestive problems,
because when that werewolf pops out of the bushes
and a wave of cortisol washes through you, your body
wants to focus its energy on sending blood to your
muscles so that you can react quickly.
Which is good, right?
But it may do that partly by shutting down digestion
or decreasing the amount of digestive secretions
and making your colon spasm; an anxious mind can
lead to an anxious gut. Stress is an even bigger risk
Stress & Heart Disease
factor in North America's leading cause of death:
heart disease, because it contributes to increased blood
pressure, heart rate, and cholesterol levels in a number
of different ways. Essentially, when your stressed out
nervous system is redirecting all of its energy sources to
your muscles and brain, it pulls flow away from your
other organs. And one of those organs is the liver,
whose job includes removing the fat and cholesterol
from your blood. So basically, when a stressed liver
can't filter properly, that extra fat and cholesterol
ends up circulating in your blood, which can settle
around the heart.
Don't believe me?
One study monitored the blood cholesterol and clotting
speed of 40 male tax accountants throughout the year,
and it found that their cholesterol and clotting rates, and
thus risk of heart attacks, increased dramatically during
the weeks before tax day as they stressed out about
finishing their work.
Pessimism & Depression
And physiologically speaking, it's worth pointing out that
some close relatives to stress, when it comes to their
effects on the body, are pessimism and depression,
which also have been linked to stress and heart
disease. Many types of studies have found that people
characterized by their optimism, happiness, love, and
positive feelings often live significantly longer than their
grumpy, dour counterparts. Researchers
don't quite know exactly how chronic negative emotional
states influence health, but it may be some combination
of lifestyle or behavioral factors, like neglecting your
health, or not taking your heart meds when you're
feeling blue, or social factors like the way the depression
can be isolating and thus prevent others from helping
you out. Or biological factors, like increases in certain
kinds of inflammatory proteins released by the immune
system in response to stress and sadness.
So in the end, while stress may not directly cause
disease, you could say that the two walk hand-in-hand.
In that way, it isn't a stretch to say that chronic stress
can kill, so go ahead
take a deep breath,
feel your emotions,
appreciate them,
but don't let them run your life.
Review & Credits
Today, we talked more about how our emotions work
and how we use facial expressions to help us
communicate. We also looked at the 2-dimensional
model of emotional experience and how anger,
happiness, and depression can affect our health.
We also discussed what stress does to your nervous
system and how chronic stress can damage the
functioning of your biological systems.
Thanks for watching, especially to our Subbable
subscribers who make Crash Course possible.
To find out how you can become a supporter just go to
subbable.com.
This episode was written by Kathleen Yale,
edited by Blake de Pastino
and our consultant is Dr. Ranjit Bhagwat.
Our director and editor is Nicholas Jenkins,
the script supervisor is Michael Aranda,
who is also our sound designer,
and the graphics team is Thought Cafe.