There are at least two possibilities here. One
is that you are getting scared by the dream and
getting a shot of adrenaline. Scary things in
dreams can cause a release of adrenaline just like
scary things when you’re awake. And what’s
scary in a dream might not really be scary.
There’s another possibility. When you dream,
your brain has to sort of disconnect from the rest
of your nervous system. Normally you would get
incoming signals from all your sensors, like the
ones in your skin and ears. But in sleep, your
brain responds to the signals that it creates.
You think you hear, see, and feel things that are
only happening in your brain. Your brain also has
to disconnect from the nerves that control your
muscles so that when you are fighting that dragon
in your dreams, you’re not running around the
house knocking things over. The nerves aren’t
really unplugged, the signals just don’t get sent,
or a tiny bit of the signal get sent, so you only
hear loud noises, or your leg twitches instead of
There’s an area in your brain stem called the
reticular formation that is in charge of
disconnecting and reconnecting the signals as you
fall asleep and wake up. Usually you don’t even
notice this, but sometimes the timing is slightly
off, so when you start to fall asleep, you feel
like you’re falling and wake up scared. Other
times you might be awake but feel paralyzed for a
few moments before the signals get going again.
Some people hear loud bangs or roars, or see
flashes of light just as they wake up. What’s
happening to you could be like that. It’s called
“exploding head syndrome.” Sounds scary!
But there’s nothing dangerous about it.
Sleepwalking is another problem that can
happen when the reticular formation isn’t quite
working right. The person is somewhere between
sleeping and waking and can hurt themselves. A
prescription sleeping drug was pretty well known
for causing this problem. Often people ate in
their sleep and didn’t remember it in the morning.
Sometimes people taking this medication would fall
down stairs, or even drive. That’s scary.
What do you think is going on? Which part of
what is happening to you seems to match these
Thanks for asking.