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from chapter 4:
Smart Belly


Your "gut brain"
Serotonin
Irritable Bowels
The Mind-Belly Connection


Your "gut brain"

As mentioned in chapter 3, your belly is home to a major portion of the nervous system — the enteric nervous system, or ENS — that lines your entire gastrointestinal tract, beginning with your esophagus.

Your "gut brain" and the brain that's up top in your skull, the "cranial brain," are derived from the same embryological tissues and produce the same biochemicals, called neurotransmitters, which turn nerve impulses into physiological action. One such biochemical, which plays a major role in relieving depression, is serotonin. Popular antidepressant drugs, such as Prozac, likely work by maintaining a generous supply of serotonin in the cranial brain.

Serotonin

Your enteric nervous system not only produces serotonin — it produces a lot of it. In fact, your gut produces and stores 95 percent of your body's total supply of serotonin. The serotonin in your gut plays many roles in managing your digestion. It starts the process by stimulating the secretion of enzymes from the pancreas. And it orchestrates the pace and rhythm of peristalsis, the wavelike muscular contractions that move food through your digestive tract.

You may already be aware of the action of serotonin in your belly. Too much or too little of this biochemical speeds up or slows down peristalsis. The result? Diarrhea or constipation.

Your gut brain doesn't share its abundant supply of serotonin with your cranial brain, but its serotonin does influence the cranial brain by stimulating the tenth cranial nerve (also known as the vagus nerve). This nerve descends from the cranial brainstem through the neck to the abdomen, allowing for two-way talk between the gut and cranial brains. The gut is the chatty one, sending up nine nerve impulses for every one it receives in return. Even with all this checking in, the enteric nervous system in the gut can operate largely independently of the cranial brain — making its own measurements and assessments, initiating its own decisions, and learning its own lessons.

Irritable Bowels

The enteric nervous system also comes into play in conjunction with an immune response that the cranial brain initiates. Here's one possible scenario: When substances threaten to breach the gut's lining — substances including stress hormones, as well as natural and industrial pathogens — the cranial brain activates the immune system's special agents, its mast cells, and appoints them to guard the gut wall. Doing their job, the mast cells secrete biochemicals, such as histamines, that induce inflammation. The inflamed tissues make the enteric nerves overly sensitive and overactive, deregulating the production of serotonin. Chronic inflammation gets on the gut's nerves. It would make anyone irritable.

Although the causes of irritable bowel syndrome (IBS) may not be well understood, many women are familiar with the signs of this functional bowel disorder. Common symptoms include abdominal bloating, cramping, and pain, and sometimes constipation alternating with diarrhea. According to the International Foundation for Functional Gastrointestinal Disorders, this particular kind of misery affects as many as one out of five adults, mostly women. Colitis, Crohn's disease, and other forms of inflammatory bowel disease (IBD) affect many more.

The Mind-Belly Connection

The connection between your mood and how your bowels are moving extends to anxiety and depression. As Dr. Emeran Mayer, Director of the Center for Neurovisceral Sciences & Women's Health at the University of California, Los Angeles, asserts, "The majority of patients with anxiety and depression will also have alterations of their GI function." He goes on to reveal that nearly three-quarters of those he has treated for chronic gastrointestinal disorders have suffered severe stresses as children. They've witnessed their parents divorcing, for example. Or they've endured a parent's death. Such events can disrupt the sense of security and connection — the sense of being mothered, being nurtured — that a child needs to digest experience and absorb nourishment throughout her life.

Compassionate body awareness, movement, and breath might contribute to healing gastrointestinal distress. How? Since your belly is home to your entire digestive tract except for your esophagus, your belly also encompasses the major portion of your enteric nervous system. When you're energizing your belly, you're interacting with this system of nerves.

As Dr. Michael Gershon, a leading investigator in the expanding field of neurogastroenterology and author of The Second Brain, says, "The gut monitors pressure." Here's what I suspect: When you breathe deeply, rhythmically contracting and expanding your belly, you're sending soothing signals to your enteric nerves. You're reducing their arousal....

2006 Self-Health Education

 

 

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