The alarm system

It’s worth remembering that the body’s reactions to trauma or potential trauma are completely unconscious. They’re not something you get to control: they’re automatic, instantaneous. Whether a threat is real or perceived, the body is doing everything it can to protect itself from harm. This is our defence system. This is how, as a species, we have kept ourselves alive and survived for thousands of years.

Our alarm system is largely unchanged from its primitive origins. It’s a biological mechanism that starts in the thalamus in our lower brain, with sensory information that’s constantly being passed at lightning speed to the limbic system where the amygdala is based.

The amygdala is often viewed as the rough and ready part of the brain. It sizes up what’s going on around us, using the data from the senses, and makes quick, no-nonsense decisions based on whether it perceives danger.

The same information from the thalamus is also presented to the nearby hippocampus. This part of the brain is responsible for memories and learning, and for choosing a course of action based on what we did in the past and how well it worked. The hippocampus takes a more considered approach to assessing danger than the amygdala. Together, in synch, the amygdala and the hippocampus handle big life-or-death episodes, as well as the aftermath of such events.

When a potential threat does arise, the information is immediately returned to the hypothalamus (which rests just below the thalamus) and a sudden release of adrenaline and cortisol follows, causing a chain of events that ensure we do one of three things: fight the danger, run away or play dead.

[See next entry for more details]