Neuropathophysiology of functional gastrointestinal disorders

Figure 4 Mechanoreceptors are connected “in-series” with the long axes of the smooth muscle fibers that form the intestinal circular muscle layer. Either contraction of the muscle or distension of the intestinal wall “stretches” the receptors and evokes firing of impulses in the sensory afferent fibers connected to the receptor. Firing frequency of the receptor increases in direct relation to the amount of “stretch” or, in some receptors, the rate at which the length changes. Mechanosensory information generated in this manner is transmitted by spinal afferents to the spinal cord or vagal nerve afferents to the dorsal vagal motor complex in the brain stem.