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Control of Motility

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Control of Motility

Part of the control of gut motility is via hormones which are secreted when the presence of a particular type of food is sensed by receptors present in the lumen of the GI tract.
A good example is the secretion of the hormone Cholecystokinin (CCK) by the presence of fatty acids in the lumen. This hormone causes the contraction of the gall bladder to allow the release of pancreatic enzymes into the duodenum.
The other major controlling system is the nervous system which functions via the sympathetic and parasympathetic nerve pathways.

The Autonomic nervous system

skeletal muscles at either end of the gastrointestinal tract (mouth, Oesophagus, Rectum, Anus) connect directly with the central nervous system through lower motor neurons and the central nervous system exerts mastery over these muscles.

The central nervous system communicates with the Enteric nervous system via the sympathetic and parasympathetic nervous pathways via chemo and mechano-receptors in the lumen.
The release of Hormones and neurotransmitters in the vicinity of the GI tract also plays a crucial role in this cross talk between the “local brain” and the central brain.

Sympathetic nervous input into the enteric nervous system, glands, blood vessels and muscles of the mucosa normally has inhibitory functions. It may cause constriction of blood vessels to control flow of blood, reduce secretion of digestive juices and hormones, and cause muscle relaxation.
Contraction of Sphincters (e.g. pyloric sphincter) is achieved by this innervation.

Parasympathetic nervous innervation terminates in enteric nervous system and stimulates most gastric functions.

The Vagus nerve innervates GI tract from Oesophagus to Transverse colon

Pelvic nerve innervates from descending colon to the anus.

 

The Enteric Nervous System

(ENS) contains as many neurons as the spinal cord and has the ability to produce every neurotransmitter identified in the Central nervous system.
This network of nerves can integrate and execute gastrointestinal function independent of the central nervous system via local release of Neurotransmitters and Hormones in response to chemical or mechanical stimuli.
Receptors that sense these responses are found in all layers of the GI tract.

It consists of two networks:

Sub mucosal plexus- this lies between submucosa and muscularis externa and functions 
to control of secretion and blood flow
Stimulate glands and epithelium
Sensory neurons respond to chemical or mechanical stimuli to produce secretomotor reflexes
Dilate blood vessels in the submucosa

Myenteric plexus-lies between the longitudinal and circular muscle within the muscularis externa and functions to:
control the function of the muscularis externa by integrating different parts of the GI tract from the Oesophagus to the Rectum.
Contraction of muscle in response to neurotransmitter Acetylcholine.

Respond to chemical and mechanical stimuli via receptors found in all layers of the GI tract.

Many reflex arcs involve interneurons that use the neurotransmitter Acetylcholine to activate receptors on motorneurons.

The Enteric nervous system is mediated by various neurotransmitters (Acetylcholine, Noradrenalin, Dopamine, and Histamine). Many medications prescribed for unrelated conditions may affect gastrointestinal motility by stimulating or inhibiting the receptors for these neurotransmitters. These medications have side effects that may cause diarrhoea, loose bowel motions, constipation or bloating.

 

 

The Enteric Endocrine system

Hormonal control

almost two dozen circulating hormones are known to modify GI tract motility. These hormones are secreted into the blood circulation by epithelial cells lining the lumen of the stomach and small intestine.
Through the circulation they are able to reach other parts of the digestive tube, pancreas, liver and brain where they can affect function.
The two main hormone “families” that influence gastrointestinal motility and secretions are Gastrin and Secretin.
The Gastrin family includes the hormone Gastrin and the polypeptide Cholecystokinin (CCK)
The Secretin family includes Secretin, Glucagon, Glicentin, Vasoactive intestinal peptide (VIP) and Gastric inhibitory peptide (GIP)

Gastrin increases lower oesophageal sphincter pressure and delays gastric emptying
Sectretin , VIP (Vasoactive intestinal peptide), Somatostatin and opiods delay gastric emptying and may decrease small intestinal transit time.

Motilin increases gastric emptying and enhances transit through the small intestine.
Cholecystokinin delays gastric emptying and relaxes the lower oesophageal sphincter in addition to functioning to stimulate secretion of bile from the gall bladder and pancreatic enzymes from the pancreas.

The Enteric Endocrine system

Hormones that promote Peristalsis:

Gastrin
Cholecystokinin (CCK)
Motilin
Insulin
Serotonin
Prostaglandins

How to heal and prevent Bowel disorders

Diet is not about what you should NOT eat, it’s about what you should include in the diet that matters.
As long as your diet includes the correct balance of plant foods containing soluble fibre, insoluble fibre and resistant starch your colon will produce the perfectly formed stool. The important next step is to evacuate this stool without straining so that the body does not suffer from the pressures created each time the bowel is emptied.

In order to heal and prevent bowel disorders you need to make lifestyle changes that last the rest of your life time.

1. Include more fluids and plant food containing soluble fibre, insoluble fibre and resistant starch in the diet so that the perfectly formed stool will be made in the colon and beneficial bacteria will flourish and eliminate disease causing bacteria and fungi.

2. Evacuate the perfectly formed stool by adopting the squat posture to eliminate the need to strain during bowel movements.

It is not possible or safe to squat on the modern raised toilet seat installed in all western homes and it is impossible to squat for any length of time if you have not done this from childhood onwards. This makes the use of any raised platforms impossible to adapt to.

The SquattLooStool is designed to allow you to adopt the squat posture while seated comfortably on your raised toilet seat.
The single best and easiest lifestyle change you will ever make, leading to a healthier body.