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So let's compare thermoregulation, the body's thermoregulation,
the brain's thermoregulation to your thermostat at home.
So here in Chicago.
We set our, or I set my thermostat
at 65.
And every time it's in winter, so it's
at 65 and then it slowly drops, because it's very cold outside.
And then it drops below some level, and the heat kicks in.
It comes back up just around 65, and then drops again.
And the heat kicks in.
So what you can see is that,
the thermostat is going to maintain the temperature.
But only as a feedback system.
We, we have to have an error before we
get back to the right, to the desired temperature.
Well, the brain is way smarter than that.
So.
What, if you took a temperature probe.
And you put it into the hypothalamus, what you would see is, let's,
let's mix our temperature, so 65, I don't know what that is in
Centigrade, but 37 C in the hypothalamus which is 98.6 in Fahrenheit.
And what you would see is that it's a rock steady,
temperature.
It never varies.
In fact, you can go outside into the cold and this will not vary.
And the reason why is because you have all these sensors.
So you're sensing the cold on your skin.
You're making anticipatory, adjustments such as vasoconstriction
of the skin to keep the warmth inside.
To keep the brain warm.
And so this is never, you could go out to zero degrees Centigrade,
you could go to negative 20 Centigrade and this would still sit there at 37.
Okay, it would never move in the hypothalamus, your skin
temperature would change, but the
hypothalamatic temperature would not change.
And this has given rise to the concept that this is a set point.
This is a temperature that the body defends.
And so there's, there's a this, this makes sense, is a very useful way to
think about it and that for instance, if
the temperature of the body increases above this.
What you get is something called hyperthermia.
And if it decreases below that, you get something called hypothermia.
But what happens is, are there any
circumstances when the set point itself changes?
And there is one very important one.
And it's called fever.
So in fever, let's, let's put it, let's put a fever down here whereas normally
our set point is at 37, you give, a
person is sick or you give is exposed to a pyrogen, something that makes a fever.
And what happens?
The te, the set point goes up, to say, 39 or 40.
And now, as the set point goes up, the temperature of the body is going to lag.
So the temperature of the body is 37, but now it's going to slowly go up
to, to 40, but right here it's below set point.
Before we get, before we got sick, when we were at
37 and the set point was at 37, we felt comfortable.
Now we're at 37 or even 38, but the set point's at 40.
What do we feel?
We feel cold.
So we feel cold, we feel chills and as you make a
fever and you do make a fever, you feel cold and chills.
When you meet the set point
you don't, you stop feeling chilled.
And then you take some aspirin, take some
antifever, antipyrogine, and what happens?
Now, the set point comes down, but the body lags, and what do you feel here?
You feel all sweaty and hot.
So the important thing is, just like we saw in perception, we don't
perceive absolute values of sound, of light, of, of anything.
What we perceive is relative.
And in the case of thermoregulation, in the case of the thermal system.
We perceive our temperature relative to the set point.
It doesn't matter what the absolute temperature of our body is,
where it matters is, is it above or below the set point.
So we are making a fever.
It's interesting to note that reptiles also make a fever.
They can't make it using metabolism as we can.
But they make it, by going and baking themselves in the sun.
And they, [LAUGH], and they end up elevating their temperature.
And the idea that many people have, is by
elevating your temperature you've actually enhanced your immune system function.
So you're helping yourself fight a, a, an infection.
So that's how fever works.
Now let's look at one last thermoregulatory problem.
And that's something that happens to probably around
80% of women that, that live through menopause.
And so that is these are vasomotor disorders,
more commonly, known of as hot flashes.
And night sweats.
So in both of these, in these situations, what's been done
is people have tried to measure, well, let's go back here.
So there's a thermo neutral zone here.
Where the, the temperature of the body can,
can change within this zone, and everything's fine.
It doesn't, if you're, if you're here it does not elicit a,
a, if you're, if you get slightly colder here it doesn't release,
elicit a metabolic response and if you go up here it doesn't elicit sweating.
And this thermo neutral zone is around one degree
Fahrenheit a half a degree Centigrade something like that.
If you me, if you try to measure that thermoneutral
zone in women with hot flashes, you can't measure it.
It's zero.
There's no thermoneutral zone.
Which means that wherever they are, they always are
on the precipice of feeling too hot or too cold.
So, let's imagine what happens.
You're sitting there at a steady rate but it, it, it ticks up imperceptibly.
And
and then you, what happens is that the body says, oh, well we
got too hot, let's send the blood to the skin.
So you send all this hot blood to the skin.
And what does that feel like?
Well I can tell you from personal experience, it feels really really hot.
And then you want to, get cool.
By taking off clothes and fanning yourself.
And, and doing things like that.
So once you, and sweating.
So once you tick up imperceptibly.
You actually make yourself hot by throwing all of this blood into the skin.
You come back down and now you feel really cold.
And so the problem with, with these vasomotor disorders is
that you just can't exist comfortably at this zero point.
That you, the strategy that I would suggest for people is to
sugge-, is to exist just below that zero point, to be slightly cold.
It's slightly uncomfortable, but it will not elicit a hot flash.
So these are, these are two examples of how
we make our, our own the temperature of our body.
In the case of a fever, it feels
uncomfortable, but it may be for our own good.
And in the case of a hot flashes, it,
it feels uncomfortable and it has no apparent benefit.
But, I think we're living longer than our ancestors
and so accompanying that are some new and different problems.
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