The autonomous rule of the second brain is constantly influenced by its previously mentioned CNS-connected communication ‘ bridges ’. This communication constitutes important motor and sensory pathways which are essentially the reason for a dynamic reciprocal influence that the gut has on the brain and by which the brain , in turn , affects the gut . This communication between the two brain centres is of primary interest to bodyworkers as we may be able to influence it substantially to support the re-establishment of balance within the ENS , the ANS and the CNS .
The myenteric plexus originates in the vagal trigone present in the floor of the fourth ventricle . It travels via the medulla oblongata within the ventral part of the brain stem , utilising the vagus pathway to reach the GIT through efferent signals .( 6 ) This neural highway of communication correlates with the cranially connected fascial sheaths that interphase with the abdominal realm and are effective access points for bodywork protocols .
The afferent neurons in turn send their signals via extrinsic ( vagal and spinal ) afferents as well as via several classes of intrinsic primary afferents ( IPANs ) back into the CNS .( 6 ) Both intrinsic and extrinsic primary afferents show mechano- and chemo-sensitivity to both physiological and mechanical stimuli . ( 7 ) It is thought that these stimuli may be directly influenced by bodywork methodologies .
Sub-populations of specific extrinsic primary afferents synapse with the dorsal horn neurons in lamina I of the spinal dorsal horn , or with cell bodies in the vagal nucleus tractus solitarius ( NTS ) located in the medulla oblongata , providing both the spinal cord and the brain with a substantial range of gut related information .( 8 ) This constitutes a key information highway for human interoceptive perception . Interoception is the process by which our body ‘ interprets , integrates and regulates signals from within itself .’( 8 ) The interoceptive signals which the GIT projects into the NTS via primary vagal and spinal afferents relay sensory signals from the gut to the brain . Only a very small proportion of those signals are consciously perceived ( e . g ., signals about ingestive behaviours or defecation ). A wide spectrum of subliminal interoceptive signals from the gut , including those that are generated by intestinal microbes , may have a significant influence on memory formation , emotional responses and affective behaviours .( 7 )
The interoceptive signals travel not only via the vagus nerve and the spinal cord , but also through chemoreceptors such as neuropeptides in the interstitial fluids , thus creating a dynamic bridge of communication between the gut and the brain . This bridge can serve to enhance the functioning of one brain centre positively influencing the other ; however , it can also transfer imbalances where pathology in the one brain centre can bring about imbalances in the other . ( 7 ) Eating disorders such as anorexia nervosa and bulimia are examples of such an expression , and demonstrate the influence the ENS wields on physical as well as mental health .
Bodywork methodologies for the ENS
Just like the brain , the ENS has demonstrated plasticity : it changes and adapts due to the influences of life such as emotional and environmental factors , changing dietary habits as well as mechanical stimuli such as diaphragmatic actions and stimulation of pressure receptors that can be activated during bodywork .( 2 )
Pressure receptors release gut-based serotonin via the mucosa , which is essential for the manifestation of a pressure-induced peristaltic response . ( 1 ) Stroking the intestinal mucosa stimulates mucosal secretion ; this is a nerve reflex that involves the stimulation of intrinsic sensory nerve cells in the submucosal plexus .( 4 )
This secretory reflex is just like the peristaltic reflex that utilizes 5-HT1P receptors and is stimulated by acetycholine , the parasympathetic transmitter .( 4 ) Stroking of the intestinal mucosa is primarily brought about through intrinsic movement of the food chyme through the lumen of the GIT . However , specific and precise touch focus may also stimulate mucosal secretion and peristaltic action within the GIT .
The vagus nerve / NTS
The vagus nerve constitutes the primary parasympathetic pathway reaching from the brain stem into the depth of the abdominal viscera . It is a bilateral nerve pathway emerging from the brainstem and exiting the cranium at the jugular foramina , the connective tissue dynamics of which can be directly influenced by bodywork techniques . The vagal pathway comprises two distinctly different nerve structures that have very specific functions and are both in relationship with the NTS . The NTS projects the vagal sensory information to several regions of the CNS , such as the amygdala and the thalamus , thus influencing memory and emotional response pathways . This nucleus is a key node for all GIT-CNS ‘ bridges ’ and is an important focus for bodywork techniques via the occipital notch .
Both vagal pathways are responsive to bodywork protocols that aim to restore improved function and balance in this
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