Rewire Your Brain: Think Your Way to a Better Life

atrial natriuretic peptide
(ANP) is produced by 
your heart. ANP tempers your body ’ s stress response by putting the 
brakes on the HPA axis and its fi ght - or - fl ight response. 
ANP does this by going through the blood - brain barrier and attach-
ing to receptors in the hypothalamus to tone down the HPA axis 
activity. Meanwhile, other areas of your brain, including the amyg-
dala, produce ANP. ANP works against the CRF, a term I introduced 
in chapter 2 , which is part of the chain of neurochemical processes 
that induce the fi ght - or - fl ight response and panic. In this way ANP 
eliminates one of the main contributors to panic. It also stems the 
fl ow of epinephrine (adrenaline) and lowers the heart rate, defusing 
another trigger for panic symptoms. All this ANP activity helps you 
feel calmer. 
Aerobic exercise can have an antianxiety effect. The physiologi-
cal changes that occur by exercising can overpower the negative 
effects of the physiological contributors to anxiety. For example, in 
one study, the subjects were injected with CCK - 4, a chemical that 
can induce a panic attack even in healthy adults with no history 
of panic. Thirty minutes of aerobic exercise prior to the injection of 
CCK - 4 lowered the panic scores, whereas resting before the injec-
tion did not. 
Exercise contributes to stress reduction by doing the following: 
•
Providing a distraction
•
Reducing muscle tension
•
Building brain resources (neuroplasticity and neurogenesis)
•
Increasing GABA and serotonin
•
Improving resilience and self - mastery
•
Mobilizing feelings in order to take action
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H e a l t hy H a b i t s : E xe r c i s e a n d S l e e p
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One study showed that a twelve - session aerobic exercise program 
reduced some of the symptoms of PTSD. This is signifi cant, because 
the symptoms of PTSD are long - lasting and intermittent. 
Exercise should be part of the overall strategy of preventing and 
treating general anxiety and PTSD. Exercise increases the levels of 
the specifi c neurotransmitters that promote antianxiety and anti-
depressant effects. One of the ways it does this is by increasing the 
neurotransmitters GABA and serotonin. Simply moving your body 
triggers the release of GABA, your brain ’ s primary inhibitory neu-
rotransmitter. Antianxiety medications like Valium and Ativan target 
GABA receptors to calm you down, but those medications have ter-
rible side effects, including depression, and they are very addictive. 
Once you remove the medication, the anxiety symptoms return — and 
at an increased level. 
Serotonin, which has been associated with depression and anxi-
ety when it is at a low level, is increased by exercise. An increase in 
serotonin level occurs when your body breaks down fatty acids to 
fuel your muscles. These fatty acids compete with the amino acid 
L - tryptophan (the precursor to serotonin) for a place on the transport 
proteins that increase fatty - acid concentration in the bloodstream. 
Once L - tryptophan pushes through the blood - brain barrier, it is 
synthesized into serotonin. Serotonin also gets a boost from BDNF, 
which also increases with exercise. 
In
Spark: The Revolutionary New Science of Exercise and the 
Brain,
John Ratey points out that regular aerobic exercise calms the 
body so that it can prepare to deal with more stress. Aerobic exer-
cise raises the threshold of physical reactions. It helps the brain by 
fortifying the infrastructure of the nerve cells by activating the genes 
that produce specifi c proteins that protect the cells from damage 
and disease. 
Exercise also raises the stress threshold of neurons. Some people 
complain that exercise makes them tired; I respond by saying that ’ s 
a good thing. In fact, you should want to get tired when you exer-
cise, because then you know that you ’ re gaining from it. You ’ re 
pushing your body beyond its comfort level to strengthen it. Ratey 
points out that exercise promotes a stress - and - recovery process 
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122 Rew i r e
Yo u r
B r a i n
that strengthens the body and the brain. At the cellular level, this 
stress - and - recovery process occurs on three fronts: 
•
Oxidation
•
Metabolism
•
Excitation
Oxidative stress occurs in the cells during the conversion of 
glucose into energy that enables the cells to burn fuel. Waste by -
products are produced when glucose is absorbed into the cells. The