Video summary
The autonomic nervous system is responsible for regulating our body's automatic functions and maintaining internal balance, operating through two primary branches that function like a car's gas and brakes. The sympathetic nervous system acts as the "gas pedal," triggering the fight-or-flight response when the brain perceives stress or danger. During activation, this system increases heart rate, speeds up breathing, dilates pupils for better vision, and redirects energy from digestion to muscles by releasing adrenaline and blood sugar. While beneficial for immediate survival, chronic activation can lead to long-term issues such as insulin resistance and metabolic disorders, while also causing tunnel vision and hindering flexible thinking by diverting energy away from the rational mind.
In contrast, the parasympathetic nervous system serves as the "brakes," managing rest, digestion, and the process of rebalancing after a stressful event to restore homeostasis. A critical component of this system is the vagus nerve, which plays a pivotal role in communication between the body and the brain. Approximately eighty percent of its fibers transmit sensory data from internal organs like the gut and liver to the brain regarding safety or stress levels, while the remaining twenty percent send signals down to the body to initiate down-regulation. This system works in opposition to the sympathetic branch to calm the body, but its effectiveness can be compromised if the sympathetic nervous system remains overactive due to chronic stress.
Another important element involved in this regulatory process is the trigeminal nerve, which senses movement and tension in the face, including clenching teeth or furrowing brows. This nerve connects with the vagus nerve in the brainstem to provide the brain with information about facial expressions and muscle tension, helping to assess whether a situation is safe. When an individual experiences chronic stress or grows up in a chaotic environment where high alertness was the norm, they may develop sympathetic dominance. In this state, the body treats constant vigilance as normal, making it increasingly difficult for the parasympathetic system to signal that the threat has passed and allowing the body to return to a state of calm.
Read the full video transcript
The first thing we want to talk about,
we're going to work from the top down,
is the autonomic nervous system. The
autonomic nervous system controls
automatic functions in our body to help
maintain balance. And I always remember
autonomic with automatic. You know, they
kind of sound similar. So, autonomic
controls automatic functions.
It has two parts. The sympathetic
nervous system, which is the stress
response or the gas pedal. So, think
your brain is having sympathy for what's
going on with you right now and it's
going to help you fight or flee.
And the parasympathetic nervous system.
That's the other one.
The parasympathetic nervous system is
responsible for rest and digest as well
as rebalancing. It's the brakes. It
helps down regulate so your body can
divert energy to regaining homeostasis
after a stressful event.
The sympathetic nervous system,
obviously, is there to help you fight,
flee, or respond quickly. It's your
survival brain.
When it's activated, your heart beats
faster, your breathing speeds up, your
pupils get bigger, so you can improve
vision. When people are excited or when
they're stressed out, their pupils will
get bigger.
Digestion slows down because now's not
the time to
send energy to the gut. Now's time to
send energy to the muscles.
And extra energy, blood sugar, is
released. Well, that can be good in the
short term. In the long term, we can see
insulin resistance and other metabolic
disorders developing.
And adrenaline floods your system. And
when we talk about people who are
experiencing a strong stress reaction,
sometimes we talk about being in a in an
adrenaline haze. When we're in that
adrenaline
haze, we tend to get tunnel vision. We
tend to be focusing on whatever we're
fighting or fleeing from. We have
difficulty with flexible thinking
because
energy's not going to our wise mind, our
thinking mind. Energy is going to our
reactions.
The parasympathetic nervous system is
the balancer. It's the rest, digest, and
rebalance branch.
The main
part of the parasympathetic nervous
system is the vagus nerve. And we've
heard a lot about the vagus nerve over
the past few years.
Uh
it works opposite the sympathetic
nervous system to help keep the body in
balance. Now, what's interesting is
about 80% of vagus nerve fibers carry
information from the body to the brain.
And from the gut, from, you know, the
liver, the spleen, everything to the
brain to tell the brain
whether things are safe or whether
things are stressful.
But there are 20% of the fibers in the
vagus nerve that take information once
the brain makes a decision, takes the
information from the brain, and sends it
down to the body.
When the vagus nerve is sending
information to the body, it is sending
information about down regulation. So,
we've only got 20% of those vagus nerve
fibers that are actually involved in
down regulation.
The other part that we want to talk
about, and it's not really part of the
uh
parasympathetic nervous system, but it
is important, is the trigeminal nerve.
And the trigeminal nerve senses movement
in the face, and it connects, you know,
to your eyebrows. It connects down here
kind of to your nose, and your upper
jaw, and then it comes down here to your
lower jaw. It senses tension. It senses
when you're clenching your teeth, when
you're furrowing your brow, or when
you're laughing.
The trigeminal nerve actually meets with
the vagus nerve in the brainstem and
says, "Hey vagus nerve, this is what I'm
picking up from this person's facial
muscles and expressions."
When the sympathetic nervous is
activated too often due to chronic
stress,
people can develop sympathetic
dominance.
Essentially, the gas pedal stays pressed
for so long that the body treats high
alert as the new normal. And we all know
people, we may be people, who
experienced chaotic home environments at
some point, and maybe
we started to believe that chaos was
normal. And we started to believe that
we were unsafe and powerless. Therefore,
high alert is the new normal. If I'm
unsafe and powerless all the time, then
I'm going to be on high alert all the
time.
When that happens, it gets easier to
overwhelm the system, and the shutdown
is much slower. It's harder for the
parasympathetic nerve to get in there
and tell the brain, or tell the body,
"Hey, you know, it it's all good.
Threat's passed. We're