Stress and the GI Tract December 17, 2010Posted by ljsteele in Behavior, Biology, Chemistry, Ecology, Environment/Conservation, Health, Neuroscience.
The mechanics of stress and the gut.
Stress is shown to have a huge effect on the body, whether or not it is experienced as an acute or chronic stress. A major topic of interest is what effects stress has on the gastrointestinal tract in organisms. According to a multi-part scientific paper entitled “Stress and the Gastrointestinal Tract”, there are many different stressors that can be examined within a variety of organisms. Examples of the stressors explored include food deprivation, fearful sounds, weather changes, and water avoidance ( an acute stressors explored in lab organisms such as mice, rats, and guinea pigs). It has also been shown that acute stressors in humans, such as pain exposure, anger, fear, and intense exercise can cause gastrointestinal shut down.
From the stressors listed above, research has explored how stress influences gastro muscles to slow contraction, thus inhibiting the processing of food. An interesting reaction to this slowing of peristaltic movement is the fact that many organisms lose control of their colon, showing defecation in response to certain stimuli such as fear and water avoidance. Corticotropin releasing hormone, also known as CRH (or CRF, as identified in the aforementioned paper), is released from the hypothalamus, and blocks the effects of the vagas nerve, while also traveling through the solar plexus, and attaching to receptors in the stomach.
Once bound, this hormone has been shown to inhibit gastro movement, and thus preventing emptying of the stomach. The difference between the stomach and the colon is that the stomach requires contraction of the muscles to push food through, whereas the colon requires contraction to keep bowel movements inside the body. With the effect of CRH binding to the receptors, relaxation in gastrointestinal muscles occur, which is why the release of the colon sphincter results. However, the results explored here were in response to short term stressors. The effects of long-term stressors have yet to be studied.
Stress and Ulcers
What does this research mean to you? Well, the results we glean from research like this offer powerful implications for human medicine and today’s society. Many people not only experience acute stress, but chronic stress as well. Short term affects of acute stress include accelerated of heartbeat and an increase in metabolism, but it is only natural to ponder the long term effects of chronic stress. We can extrapolate from the results of acute stress that it would make sense that we, as humans, would not want these effects to be long lasting. Major problems would arise with the decrease of gastro movement. Problems manifest from a build up of bile and stomach acids in the stomach. Since gut motility is decreased when stressed, less movement would mean that more bile, which is highly acidic, would sit in the stomach longer and could lead to stomach or intestinal ulcers.
Chronic stress can also lead to a decrease in the immune system of the organism as well as a decrease in the second messenger systems within the body. An example of this effect on a second messenger system is the attachment of CRH to CRH-receptors in the solar plexus. The binding of these receptors causes the effect of the decrease in gastro movement.
How much stress is too much stress?
Lastly, with chronic stress and chronic stimulation of the CRH/CRF system, we might see a scenario in that the more that these receptors are activated, the more desensatized they can become. This could cause problems for people and their response to stress. If the are “desensitized” this may mean that these people have a problem when trying to properly responding to an acute stressors when needed.