The stress response is a complicated process. It involves our nervous and endocrine systems and it stimulates changes in a variety of body processes, including blood pressure, heart rate, muscle tension, and bowel functioning. It is the changes in bowel functioning that tie the stress response and IBS together.
The Brain-Gut Connection
In response to a perceived stressor (external or internal), various parts of the brain begin to communicate with one another, including the sensory cortex, the thalamus, and the brain stem. This process then triggers a response along two major bodily paths. The first is the hypothalamic-pituitary-adrenal axis, resulting in an increase in hormonal secretions, particularly the hormone cortisol.
The second path is the autonomic nervous system, which releases adrenaline (epinephrine) and noradrenaline (norepinephrine) causing cardiovascular, muscular and digestive system changes. These two pathways directly affect the network of nerves found in the bowel, known as the enteric nervous system.
This process, which starts with a perceived stressor, followed by a brain response, and resulting in stimulation along the two pathways down to the gut, illustrates the importance of looking at the stress response in trying to understand the dysfunction that manifests as IBS symptoms.
Physical Changes of the Stress Response
The stress response triggers the following physiological changes:
Heart rate increasesIncreased respirationIncreased muscle tensionInhibition of the immune systemDelay in stomach emptyingIncrease in the speed of colonic contractionsRelaxation of bladder muscles
Research
In an attempt to find effective treatments for the symptoms of IBS, researchers have been investigating the various substances that are released during the stress response. One substance that appears to have major significance in the stress response is corticotropin-releasing-factor (CRF).
CRF is a family of peptides (molecules that link amino acids) that are found in both the brain and the gut. In the brain, CRF receptors are found in the areas related to digestion, emotions and the autonomic nervous system. In the gut, CRF act within the colon to increase mucous and water secretion, affect the speed of colon contractions (motility), and appear to be related to the experience of abdominal pain.
It is hoped that a better understanding of the role of CRF will lead to refinements in the development of medications that target IBS symptoms.
