Panic attacks are extreme manifestations of anxiety, which are intermittent and discreet episodes where you experience increased heartbeat, chest pounding, chest pain, heart palpitations, shortness of breath, numbness and tingling in your arms and legs, excessive sweating, tunnel vision, muscle tension and trembling.
Panic attacks can occur in different situations. If you have social anxiety, then exposure to social situations can induce a panic attack. If you have a fear of an object (i.e. spiders) or situation (i.e. flying), then exposure to your feared object/situation can also lead to a panic attack.
Finally, if you experience uncued, random and spontaneous panic attacks, then this reaction may be a manifestation of panic disorder.
So what’s the neurobiology behind panic attacks? Well, a panic attack is a manifestation of your fight or flight response being triggered intensely, for a brief period of time. The fight or flight response is illustrated by the following flowchart:
So when you sense fear, this triggers the amygdala, which is located in the temporal lobes of the brain. The activated amygdala then activates both the sympathetic nervous system (neuron-based) and the HPA axis (hypothalamic pituitary adrenal axis) (hormone-based).
In activating the sympathetic nervous system, the amygdala activates the locus coeruleus, which is located in the brain stem. The activated locus coeruleus in turn sets off the sympathetic nervous system, where the sympathetic neural impulse sets off various organs directly, such as the heart (increased heart rate and contraction), blood vessels (dilates in skeletal muscles, constricts in gastrointestinal organs), sweat glands (increased perspiration), and eyes (dilates pupils).
In addition to the above organs, the sympathetic neurons directly innervates the inner part of the adrenal glands, called the adrenal medulla. The adrenal glands are located on top of each kidney. When the sympathetic neurons activate the adrenal medulla, adrenaline (epinephrine) and noradrenaline (norepinephrine) are released into the bloodstream.
The circulating hormones of adrenaline and noradrenaline then act on various organs such as the heart (increased heart rate and contraction) and the lungs (dilates the bronchioles, or air sacs) to further perpetuate the panic attacks symptoms.
In activating the HPA axis, the amygdala activates the hypothalamus (located just above the brain stem), which in turn secretes corticotropin releasing factor (CRF). CRF travels to the pituitary (located at the base of the brain), and activates it to secrete adrenocorticotropic hormone (ACTH).
ACTH then travels to the adrenal cortex, which is the outer part of the adrenal glands. ACTH activates the adrenal cortex to secrete cortisol, another stress hormone, into the bloodstream. Cortisol is involved with increasing the supply of blood glucose to fuel the panic attack and also suppresses the immune system.
Another manifestation of a panic attack is hyperventilation, where you are breathing fast and can’t seem to catch your breath. As a panic attack starts, you will breathe faster and become short of breath, as the fear-activated amygdala in turn activates the parabrachial nucleus, which is located in the brain stem.
As your rate of breathing accelerates, you will resort to chest breathing, instead of belly breathing, or breathing from your diaphragm muscles. As you increase your rate of breathing, you start to hyperventilate, where you are blowing off too much carbon dioxide (CO2) from your chest breathing.
This situation leads to respiratory alkalosis, which is a rise in blood pH, and can cause numerous symptoms adding to the panic attack, such as dizziness, weakness, fainting, headache, tingling in the hands and feet, and seizures.
The remedy for hyperventilation with a panic attack is to breathe into a paper bag, so that you can recycle the CO2 back into your bloodstream, normalizing your blood pH, and hence reducing your panic attack symptoms and normalizing your breathing.
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Flowchart reproduced with permission from AnxietyBoss.com.