Over the past week, I've been reading this very interesting (for me) book.
In order not to misrepresent the author, I'm going to quote some paragraphs
from the opening chapter.
For animals like zebras, the most upsetting things in life are acute physical
crises. You are that zebra, a lion has just leapt out and ripped your stomach
open, you’ve managed to get away, and now you have to spend the next hour
evading the lion as it continues to stalk you. Or, perhaps just as
stressfully, you are that lion, half-starved, and you had better be able to
sprint across the savanna at top speed and grab something to eat or you won’t
survive. These are extremely stressful events, and they demand immediate
physiological adaptations if you are going to live. Your body’s responses are
brilliantly adapted for handling this sort of emergency.
The half of the autonomic nervous system that is turned on is called the
sympathetic nervous system. Originating in the brain, sympathetic projections
exit your spine and branch out to nearly every organ, every blood vessel, and
every sweat gland in your body. They even project to the scads of tiny
little muscles attached to hairs on your body. If you are truly terrified
by something and activate those projections, your hair stands on end;
gooseflesh results when the parts of your body are activated where those
muscles exist but lack hairs attached to them. The sympathetic nervous system
kicks into action during emergencies, or what you think are emergencies. It
helps mediate vigilance, arousal, activation, mobilization. To generations of
first-year medical students, it is described through the obligatory lame joke
about the sympathetic nervous system mediating the four F’s of
behavior—flight, fight, fright, and sex. It is the archetypal system that is
turned on at times when life gets exciting or alarming, such as during stress.
The nerve endings of this system release adrenaline. When someone jumps out
from behind a door and startles you, it’s your sympathetic nervous system
releasing adrenaline that causes your stomach to clutch.
The other half of the autonomic nervous system plays an opposing role. This
parasympathetic component mediates calm, vegetative activities—everything but
the four F’s. Sprint for your life across the savanna, gasping and trying
to control the panic, and you’ve turned the parasympathetic component down.
Thus, the autonomic system works in opposition: sympathetic and
parasympathetic projections from the brain course their way out to a
particular organ where, when activated, they bring about opposite results. The
sympathetic system speeds up the heart; the parasympathetic system slows it
down.
Another important class of hormones in the response to stress are called
glucocorticoids.
The body synthesizes these glucocorticoids, but we can also be given
synthetic glucocorticoids, a good example being Prednisone that is a
potent synthetic corticosteroid used to quickly reduce inflammation,
suppress an overactive immune system, or replace natural cortisol. It is
prescribed for a wide variety of conditions, including severe allergies,
asthma, arthritis, and autoimmune diseases like lupus.
The
neurologist1gave me a referral for a head CT, using a contrast dye. In Israel
(and probably elsewhere), someone who has a bad reaction to such dyes is
considered to be allergic to Iodine, although this is not accurate as iodine
is a required micronutient for the thyroid gland. Reactions to intravenous
X-ray/CT contrast media are typically caused by the physical properties (e.g.,
hyperosmolarity) of the solution itself, not the iodine it contains. I am not
sure whether I am 'allergic to Iodine'; it is written in my medical history
and so everyone has to be careful. I underwent a procedure some 40 years ago
to do with my kidneys and had a bad reaction to the 'iodine' although whether
that is considered to be severe enough to be an allergy is uncertain. I have
an appointment with an allergy doctor in August to settle this once and
forever.
The connection between this scan (which was done yesterday) and the
glucocorticoids is that I had to undergo a 'preparation protocol' that
involved taking prednisone three times at various hours of the day along
with another medicine an hour before the test. Everyone at the hospital
checked that I had taken the medicines although obviously they had to rely
on my answer.
I am going to go into detail about what I felt from the scan onwards,
primarily so that I will have it documented. During the test itself, the
only abnormal thing that I felt was as if part of my testicles had been
lowered into warm water; the rest of the body felt fine. My hands were
shaking slightly but that's something that I've noticed over the past few
weeks. After I got home, I took the dog for a walk then had a light supper.
I felt slightly warm but I thought that this was due to walking the dog. By
the time I came to measure my blood pressure at 9 pm, I was surprised to see
that it was high (relatively for me) at 125/82 with a pulse of 102. For
comparison, the readings on Sunday evening were 103/78 and pulse 77. When I
got into bed, I felt quite warm, despite the air conditioner, and slept for
some time uncovered.
Obviously the prednisone had activated the sympathetic nervous system, and
the iodine was having its effect.
Going back to zebras and why they don't have ulcers: humans have both
external sources of stress and internal souces, or psychological stresses.
Unfortunately, the body can't distinguish between the two sources and so the
sympathetic nervous system gets unnecessarily mobilised, moving blood to our
arms and legs and taking it away from other areas of the body. One familiar
source of psychological stress is how much control we feel we have over our
lives, otherwise known as locus of control. Those with a low locus of
control have more stress than those with a high locus.
My job affords me with a very high locus of control, but I remember that
when I was in the army (compulsory service and reserve duty) I had a very
low locus, and I used to say that if something were about to happen and I could
think of two alternatives, the army would always choose a third option which
would be worse than anything that I could think of.
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[1] 2095
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