The neurobiology of panic disorder is rooted in the fear circuits, which is mediated by the amygdala, an almond-shaped structure in the temporal lobes of the brain. In panic disorder, this fear circuit has malfunctions intermittently, and these malfunctions are unexpected and random. These unexpected malfunctioning of the fear circuits are what causes the unexpected panic attacks in panic disorder.
In addition to the fear circuit malfunctioning unexpectedly, the worry circuit based on the CSTC (cortico-striatal-thalamic-cortical) circuit is hyperactive due to the anticipatory anxiety about having the next panic attack. So this overactive worry circuit triggers and kindles the fear circuit, which increases the intensity and frequency of future panic attacks.
So knowing this neurobiology of panic disorder serves to help you eradicate your anxiety. For more detailed self-help on eradicating panic disorder, please obtain a copy of Anxiety Protocol.