LECTURE 6

G.I. Tract - Control →

Principle of Control:

Aim: To maximise absorption of nutrients, whilst minimising damage from toxins.

Achieved by:

• Regulating motility.

• Controlling secretion of digestive juices

GI Tract Gut o the idea of gastric motility or the gastric tract really is to maximize the absorption

of nutrients as necessary obviously for energy and for maintenance of tissues.

And it's achieved.

by regulation or using nerves hormones

by controlling secretion of digestive juices from the pancreas and from gastric

glands.

Has little ability to control absorption. So the epithelium is Shed from time to

time.

There are some influence by hormones such as pyroxene, which obviously control the

the basal metabolic rate.

but

the way that the the GI tract has evolved makes it an Excellence scavenger. So it's

it's evolved at times when food was scarce. So it's evolved to really maximize the

absorption of nutrients.

So surprisingly functions governed by the gut content not by the needs of the body

of status of the body.

So the way that the gut manages that is by sensing the Lumen content so the volume

and also the the types of food in the stomach, so

It relies on the kind of receptors in the epithelium which distend and then some

send messages to the brain to then respond to that.

It relies on the chemicals in the food that we eat which obviously will have an

influence on the osmolality. So the osmoreceptors will detect changes in osmolality

chemoreceptors, which respond to changes in acidity. So that will influence the

secretion of different hormones and enzymes.

And then the products of digestion themselves or feedback by chemoreceptors. So

there's lots of specific receptors which will feed into this system and because

of the abundance of receptors it effectively makes the intestinal epithelium the

largest sensory organ in the body.

So when these receptors respond to signals, they will initiate long reflexes. So

these are reflexes which go right up to the brain the brain stem and but also the

rush short reflex is so it's not necessary to send signals right up to the brain.

Some of these reflexes are initiated through the enteric nervous system, and it's

going to be a large focus on that in this lecture.

Of course, there are also hormones which bind to specific receptors and that they

they will cause changes in motility and also paracrine transmission. So these are

factors which don't have to travel through the blood they can diffuse over short

distances to cause effects.

So if we think about the GI tract, it's got the same basic structure throughout.

So we've got secretory cells in the mucosa of there. And then we've got layers of

smooth muscle and between those we've got these plaques eyes. So these bodies nerve

cells which are able to influence the the

layers around them

So largely are we going to smooth muscle and there are stink tutors as well, which

can regulate the movement of food circular muscle is constrictor. So that tends

to narrow the tube which squeezes food along.

And the longitudinal muscle around the outside can either shorten or lengthen and

again that will push food along the GI tract.

So this slide shows the structure the track. So if we look at the layer closest

to the Lumen there, so it's the mucosal layer. It's consists of the epithelium surrounded

by lamina propria and then surrounding that got the muscularis mucosa and you can

see that embedded in the mucosa. We've got some submucosal glands. So these are

small glands and also duck.

That's that feed into the Lumen here. We've got some lymphatic tissue. So that's

really important for a man a human or a logical point of view clusters of lymphocytes

will deal with microbes and foreign organisms there if we go out to the submucosa,

you'll see the submucosa is itself has got plans which feed into the Lumen and then

we've got the submucosal plexus or Texas or

of Meisner. So this is cluster of nerve cells which will control secretions and

also blood flow.

And then around that we've got two layers of muscles of got circular muscle and

longitudinal muscle and in between those muscle layers, we've got the my entire

court or backs plexus and these are largely this is largely to control motility

in the guts of controls the contraction of these muscles and then around the outside

but largely connective tissue, so that holds the guts in place.

So we've got intrinsic nerves. So autonomic nerves which are nerves which control

the gut motility. They will fine-tune the contractions controlled by the the my

enteric Lexus.

So parasympathetic nerves impacting on the enteric nervous system largely increased

motility. They will increase secretion from glands.

They're responsible for long reflexes. So we have sensory vagal fibers, which will

feed back to the brain stem.

Stimulate efferent fibers are sympathetic parasympathetic fibers, which will then

cause contraction of these muscles. So 80% of these Bagel fibers are actually sensory.

If we look at sympathetic innervation, it largely reduces motility and it will reduce

blood flow. So we know that this is a an important function because if you need

fight or flight if you need blood supply to be direct to the muscles, obviously,

you don't want to get you need to get that blood from elsewhere.

Digestion absorption is not important at that time. So therefore largely the GI

tract gets shut down in order to prioritize the muscles.

We think about the origin of this extrinsic nerves. So sympathetic nerves come from

the for a so lumbar regions of the spinal cord preganglionic neurons feed into the

sympathetic chain, which runs alongside the spinal cord and the postganglionic neurons

will stimulate the Mind tarek plexus they'll

late nerves in the submucosal plexus and they're also directly stimulate the epithelia

epithelial cells and this occurs throughout that the GI tract

and obviously the the neurotransmitter postganglionic neurotransmitter is noradrenaline.

We look at the parasympathetic Branch. You can see that the preganglionic nerves

actually signups in the the - Eric metaxas itself.

in the submucosal plexus as well and the interesting thing about the parasympathetic

nervous system is it's divided up into the the brainstem nerves which will feed

the esophagus and the stomach whereas the sacral region gives rise to nerves which

will stimulate the distal part of the large intestine down to the

now to the anus

and these are going to influence activity in the flex site.

Also in the the submucosal plexus the nerves here have their own transmitters. So

as well as acetyl choline, we've got nitric oxide gastric releasing peptide and

vasoactive intestinal peptide.

So these are all on your GI hormones table that I put on that boat last week.

We look at the structure of the the GI muscle like other smooth muscle is going

to add in a regular arrangement of actin and myosin.

And the reason for that is that it's got its own basil tone. It can still generate

tone when it's stretched.

The cells are very long and thin.

So five hundred to Five Hundred microns by five microns and the grouped into bundles

of cells, which are got a diameter of about two hundred micrometers. The cells are

electrically coupled. So they have Gap Junctions which allowed the flux of electrolytes

between cells and what that does is it generates a functional unit. So the cells

are able to communicate with each other and they are able to contract

in a unit

in the GI tract, the membrane potential is is unstable. So it varies by 5 to 15

millivolt. And that's really important because it allows the generation of slow

waves, which will generate this sort of resting tone. And this slow wave activity

could be modified to cause larger contractions.

So they were determined the frequency of contractions. So for example, the frequency

of these slow waves and the stomach is is 34 minutes. So every 20 seconds, whereas

it increases in the duodenum up to 12 slow waves four minutes.

And as I mentioned that causes a bay producers of Basil electrical Rhythm amazing

basic electric rhythm.

So resting membrane potential of these cells is between - or T and minus 60.

And the slow waves occur all the time.

And what happens is if the slow wave increases if we get depolarization here if

the depolarization reaches the threshold there it will generate an action potential

known as a spike potential.

And frequency of these Spike potentials depends on the extent of depolarization.

If we look at how that's transfers to contraction during slow-wave. There's there's

very little contraction when these spikes occur. We get small contractions there

and the size of the contraction is dependent on the frequency of the spikes and

the generated up to a point here where we get maximum contraction.

So the size of these slow waves is modified by nerves but also hormones.

And we rely on these voltage-gated calcium channels. So this Spike potentials and

unlike neuronal Action potentials. They're not just caused by sodium influx. They

also are reliant on calcium influx. And what that does is it extends the duration

of the spike potential and the calcium takes longer to reach.

Which batik?

Once calcium has entered the cells it binds to calmodulin and this initiates a contraction.

so if they like the heart the

there is a pacemaker or the pacemaker regions within the gut and the cells which

make up this pacemaker regions of called the interstitial cells of kejal. And this

is a scanning electron micrograph here. So this whole that here is that the interstitial

cell of occasional it's got this fusiform body and then it's got these projections

coming off that and these projections will interact with the my enteric nervous

that my

The enteric nerves here and underneath here. You can see the interaction with the

smooth muscle. So these are smooth muscle fibers underneath.

so

these ICC cells you can see how and it's cartoon how the interacts with the neurons

of the monitoring of access. They have mechanic sensors on them. They have receptors

for neuropeptides.

And they also interact with the smooth muscle cells here. They can interact with

blood vessels. So they control control blood vessel diameter as well.

And basically they generates these slow waves and this is then transmitted to the

the smooth muscle.

So how do those slow waves look and how do they relate to the activity in the smooth

muscle so you can see here? We've got an action potential generated. So at this

point here voltage-gated calcium channels open up calcium rushes in here up to this

maximum.

And then we've got non-selective cation channels open too cause this Plateau phase

and then repolarization occurs at this point here.

If we can if we see how that affects the activity in their smooth muscle cells,

you can see that the smooth that the slow waves in the smooth muscle and much smaller

in amplitude. But this one's got a spike at the beginning which is due to l-type

calcium channels opening. So there's an action potential here, which is superimposed

on the slow way.

And what that does is it causes spread of depolarization. It causes calcium entry

into the smooth muscle cells and that will then cause contraction to occur. So these

ICC sells his pacemaker regions they will occur in the submucosal both submucosal

plexus they will occur in the my enteric plexus.

And they can occur in the smooth muscle itself. So between layers of smooth muscle.

And they're very important for generating difference.

Different rates of slow wave activity in different tissues. So the the cells in

the esophagus would be different from the cells in the colon for instance.

So, how are these slow waves modulated so food, we call stretching of the smooth

muscle.

And this will stimulate nerve and hormonal activity which can then increase or reduce

the maximum or the size of the maximal depolarization.

So we've got both intrinsic nerves from the enteric nervous system and extrinsic

nerves from the autonomic nervous system.

Acetylcholine release will cause depolarization so that will increase the size and

frequency of the spike Essentials and that will lead to contraction of the smooth

muscle.

in terms of hormones gastrin and motel in will also cause depolarizations so they

will increase the rate of

these Spike potentials or action potentials

if we look at the neurotransmitters released from the enteric nervous system or

nitric oxide of our Zoo active intestinal peptide. These will lower the memory potential

because it he hyperpolarization and this will reduce the contractions occurring

in in terms of hormones secretin and gastro intestinal peptide will also cause hyper

ization, so they'll reduce

So I wave activity.

So gastrointestinal hormones short chain peptides these include secretary and gastrin

and cck. So these are all secreted by enter our Endocrine cells, which found in

the mucosa.

Secreted into the blood and these Target various regions of the GI tract and also

glands but interestingly they've also been shown to have effects on the central

nervous system.

So cck for example has an influence in society in satiety or hunger and it's also

been implicated in anxiety and depression so cck secreted in the jejunum and it's

has its actions on the pancreas gallbladder and stomach as we've already seen.

So These intro Endocrine cells, so the Endocrine cells of the guts full of that

1% of the epithelium. So they're very distinct cells.

They have meccano sensors. So they have these microvilli and these will sense specific

chemicals in the lumen.

They will respond to the the microbiota so microbes in the guts will cause what

produce fermentation products short-chain fatty acids such as acetate and that will

stimulate the interest site.

To to produce protective functions so we can increase the rate but by producing

hormones, it can increase the rate of contraction of the guts and therefore it can

very quickly clear the guts of any toxins.

90% of these anthro Endocrine cells are term dentro chromaffin cells, and these

are cells which secretes the hormone serotonin or 5-ht.

The remaining 10 percent secrete other hormones that are already mentioned like

cck and secretary.

So how do these entro chromaffin cells function?

So the stimulated by distention so they've got the canno receptors.

This causes the production of 5-ht, so tryptophan is used to express 5-ht these

5-ht stored in these circles.

an influx of calcium will cause these vesicles to fuse with the basolateral membrane

releasing serotonin into the

the cleft their serotonin will then stimulate neurons by 5-ht three receptors.

The the end of this signal is caused by reuptake. So we've got sodium chlorides

dependent react take transporter named cert.

And that will remove 5-ht from the synaptic cleft there terminate the signal.

So what about this receptor? So this was properties of this receptor is discovered

in 2021. And it was important enough that the the author's to get The Nobel Prize

so they discovered that this Piezo channel. So calcium channel had meccano sensory

properties and that was discovered it in a mouse model. So by causing distention

of the

Gut and just distension of this meccano sensor.

It caused a massive influx of calcium and calcium will then bind to these vesicles

and that causes exocytosis to occur.

Think about paracrine transmission. So short hormones don't enter the blood they

will too few directly through the interstitial fluid very good of example of that

with histamine. So we know that histamine will diffuse to the parietal cells because

in gastric secretions,

Prostaglandins are also important paracrine factors. So they stimulate bicarbonate

mucus secretion in the gut.

And that that occurs in response to distension. I don't know if this tension sorry

because in response to acid secretion and also ischemia in the gut Brandy Keenan.

Is released in response to irritation of the gut wall that binds to be rich be receptors

which will in turn stimulate the release of prostaglandins. So particularly prostaglandin

E2

divisions between nerves hormones and paracrine factors are often lured in the guts.

So write the focus now on how food is moved from the the mouth right through to

the anus.

Obviously the mouth is important in reducing the size of particles food particles

increasing the surface area allowing the food to mix with the saliva and start of

digestion.

So the first process of motility is

Conducted by the Tongue so that tongue big muscular organ pushes the food to the

back of the throat where it is pushed onto the hard and soft palate and this is

known as the oral stage swallowing and its voluntary. So we have control over that

stage.

So this point here the Airways are opened still breathe, but the upper esophageal

sphincter is closed here. So the food can't at this point move down into the esophagus.

Second phase is known as the pharyngeal days. It's part of the swallowing reflex.

It's an involuntary days. And what happens here is we get elevation of the soft

palate the back of the mouth here and what that does is it blocks off the nasal

cavity, so it's stops nasal breathing from occurring.

You get contraction of the pharyngeal muscles that moves the bolus down through

the pharynx and there's actually a series of pharyngeal constrictors and they contract

in sequence from Superior from the top down to the bottom moving the food down through

the pharynx.

We also get closure of the glottis. So the the bolus of food bends the epiglottis

here. So that covers the trick here stop food from going down the wrong way and

at the same time the upper esophageal sphincter relaxes and opens and that and then

allows the bolus to enter the esophagus.

Third part the esophageal phase is also an involuntary phase and this involves peristalsis.

So coordinated contractions of the esophagus move in the food down towards the stomach

and as the pressure increases their it causes opening of the lower esophageal sphincter

allowing the bonus to enter the stomach.

And this is termed receptive relaxation because the fundus of the stomach relaxes

as swallowing occurs. This is mediated by vasovagal reflex. So those impulses are

taking up to the spinal cord and then the vagus nerve then stimulates relaxation

to occur allowing food to enter the the stomach.

As we know stomach is the main story to organ. It's got the ability to increase

its size greatly.

So first of all, the the food enters the the fundus talked about receptive relaxation

also food moving into the stomach cause some distension and that will buy a feedback

negative feedback mechanism will cause the release of nitric oxide which will relax

the muscle allowing the stomach to expand to about 1.5 liters.

So I mentioned the the basic of basal electrical Rhythm. That occurs is very very

slow.

Rhythm of three slow-wave contractions per minute. So what happens is we get some

very weak peristalsis occurring

and this will move the food down towards the antrum.

as it moves down towards the antrum the

waves of peristalsis get stronger

At the same time the pyloric sphincter is closed so increases the pressure in this

region. So we're getting food basically shove towards the pyloric sphincter. It's

then coming. It's being forced back again. And it's this causes a churning action

to occur, which is really important because it mixes the food with the gastric acid

and pepsin there.

So the pyloric sphincter itself will open very slowly. So we will allow about three

mils per minutes to enter the the duodenum that's really important because we don't

want to overburden the duodenum with masses of acid.

And because of this it retains particles which are greater than 2 mm in diameter.

So will only allow that the most digested food to went to the duodenum.

So how is gastric emptying actually regulated? So the food is in the stomach for

about two to five hours normally.

As the stomach becomes distended we get a release of gastrin and also stimulation

of nerves which will ultimately increase emptying so allow the power of sphincter

to open.

but

emptying of the stomach it is largely controlled by the the duodenum so as the stomach

starts to empty.

Get food entering the duodenum so peptides and hydrochloric acid will stimulate

nerve reflex, which will reduce mixing.

And food entering the peptides and an acid entering the duodenum will also reduce

empting. So it will reduce the tone. Sorry increase the tone of the pyloric sphincter.

We also get the release of hormones such as cck and secretary secretary in response

to fats entering the duodenum.

And these will also feed back to the stomach reducing the the motility.

And in the case of secretin inhibiting gas transactions over reduce stomach acids

release.

So this is a really important protective mechanism as I say, we don't want kind

to enter the duodenum the duodenum too quickly because it will cause too much acidity.

It will inhibits the enzymes pancreatic juice pancreatic enzymes, but it will also

damage the the duodenum.

So the rate of emptying would depend on the constituents of the meal. So if it's

a very high fat meal then gastric emptying will be reduced if it's a larger carbohydrate

meal and gastric emptying will be speeded up.

So when the food enters the small intestine Transit would take between two and four

hours that the function here is further mixing of the the kind with with enzymes

making sure it circulates through the Villi the small intestine giving it maximum

time for absorption to occur.

So in terms of propulsion obviously moves quite slowly through the small intestine,

so that's that's a minor role.

the two types of movement that occur segmentation which is a

responsible for mixing has a large has a small component component of propulsion

and peristalsis, which is really strong muscular contractions, which will move the

food alone.

So segmentation is

Initiated by circular muscles so we get concentric contraction circular muscles

at regions along the small intestine. So we're talking about very small regions.

So if we get contraction at behind and ahead of the bolus of food, then it will

keep the food in this region. So it will segment the small intestine and the importance

of that is that

Is that the foods got nowhere to go so it circulates?

Round and round and that's really important for mixing. It's important for increasing

the the contact with the dura Dura Dino mucosa there for absorption to occur.

And it's controlled by the basic electrical Rhythm and distension will cause a reflex

that contraction there via the my enteric taxes. So this is largely controlled by

the - Eric faxes. It's a local contraction.

So the the basic electrical rhythm in the duodenum is is around 12 slow Waves per

minute. We compare that to the stomach where it was three. So it's quicker than

the stomach and it slows as we progress through the small intestine. So by the time

we reached the ilium it slow down to these movements are are slower.

And what that does is it gradually moves the kind forward along the duodenum.

So the other major contraction occurs is peristalsis, which is I'm sure you've come

across before so this has got a propulsive roll. So we get a ring of contraction

which occurs behind the kind so it can't move backwards and ahead we get relaxation.

So that sort of squeezes the food along a bit like a toothpaste tube and this will

occur any point along the smooth small.

in testing

So it's initiated by distension as the food moves through it stimulates mechano

receptors, which will then cause a reflex contraction to occur.

So the third then travels on few centimeters point five to two centimeters per second

along small intestine. Obviously, it can be speeded up by neurons neural or hormonal

factors and if you get infected diarrhea then

The the toxins can actually cause a very powerful peristalsis. So the the kind could

be moved through the small intestine in a matter of minutes in response to toxins.

So that's really important mechanism for ridding the body of any toxic agents.

So the sphincter muscles are are under independent control. So Spink tastes mentioned

the sphincter of oddi. So the important thing about sphincters is that they are

able to relax when all of the smooth muscle around. It is Contracting and that's

really important because

Obviously if you got a peristaltic wave you don't want it to be stopped by a sphincter,

which is also Contracting that the sphincters need to open up to allow movement

to occur.

Through this morning testing.

So there are a number of important reflexes that occur in the intestine.

And the important thing is that they can control movement throughout the whole GI

tract.

So the first important one is the gastro ileal reflex. So that occurs in response

to distension of the stomach's as food enters the stomach it will feed on to the

duodenum to increase motility of the duodenum.

So food gets pushed through the duodenum through the small intestine until it gets

to the the interface with the large intestine cecum and the ileocecal valve relaxes

at allowing a small amount of chi through it.

But activity in the stomach is actually largely regulated by what happens in the

small intestine. So as the ilium becomes distended this will feed back to reduce

gastric motility.

And that's important to avoid overburdening the the duodenum.

The ileocecal valve allows food from the ilium into the cecum so it from small to

the large intestine and importantly it doesn't allow backflow. So we don't want

food to go back from the large intestine into the small intestine. It's normally

closed but if we get a wave of peristalsis

Meeting the ileocecal valve then that will allow the ileocecal valve to relax allowing

contents into the large intestine.

It's also part of the gastro allele reflex.

So by the time the the undigested food reaches the large intestine of the: it had

most of its nutrients removed. So the function largely is absorption of the water

and salts.

So also go to a storage function so

Bearing in mind is only a few hours spent in the small intestine. The undigested

food can spend on average 33 hours in the large intestine. So it moves very slowly

through the large intestine.

And in order for water and salts to be removed, we need further mixing to occur.

It needs to be able to spend a lot of time.

Close to the absorptive surface of the mucosa.

So we get this type of segmentation called horse tration house duration and

The slow wave activity is 8 per minute.

And what happens is we get very strong constriction of

the circular muscle at different points along the large intestine and what it does

is it to basically pinches off to 25 cm segments of the the large intestine.

And the way that the longitudinal muscle is arranged is in three strips called taenia

coli.

So it's pinching off parts of the the large intestine and anything which is not

being stimulated in between those points and then bulges out.

to provide these ovoid segment sort of very very

again a bit like a balloon. If you've got one of those long long thin balloons twist

a bit and the the bit between the twist will bulge out.

forming how strong or how stations

and what happens there is that the the fecal material gradually gets turned over

bit like it in a washing machine and it allows for water and salts to be removed.

So this shows this patient is had a barium meal. So the white but here is where

the the barium is moving through its highlighted where these folds occur between

the pinch ticks.

So

if we want to find a good model for investigating slow wave activity Spike potential

activity in the gut and can look at different species and some species have a very

similar activity to humans and others have very different. If we look at different

parts of the guts will see that the activity there is between different regions

of the gut. So what this slide shows is actually the meringue guts Mouse go.

Utz looks fairly similar to a human guts there. So Mouse models of

the gut useful models to investigate how activities generated

That's the colon.

So between the ileocecal valve and the transverse colon get gradual movement of

undigested material and this is by those how strong contractions which occur.

As we get to the descending colon between the descending colon and the rectum.

The movement has changed slightly. So we get a type of peristalsis called mass movement

mass movements and these occur about three to four times per day and then initiated

by distention of the the large intestine.

So what happens is we get his rings of contraction and it will Propel the chyme

for quite a long distance along the the large intestine.

We get this contractions which will occur for for up to a minute at a time followed

by a period of relaxation and these occur for a period of about 10 to 30 minutes

three or four times to per day usually after meals

And this this obviously propels the undigested material or the feces by this point

quite a long way along the length of the large intestine in ulcerative colitis.

We get very intense mass movement, very strong aerostatic contractions, very uncomfortable.

So at the end of the large intestine we come to the rectum, which is usually empty

or almost empty.

So contraction of the the top of the rectum will impede filling of the rectum. So

it keeps its fairly empty.

So it only fills up in response to mass movements moves fecal matter into the rectum

that will then distend the walls the rectum initiating this wreck toast think tarek

reflex.

And what happens there is the internal sphincter, which is smooth muscle. So it's

under involuntary control.

That will stop start to open up and it's only then at this point of the external

sphincter, which is under conscious control, which will stop thesis from entering

the anus.

Then the internal sphincter will regain control and the the urge to defecate will

will go until there's another mass movement which forces more visas into the rectum.

So the defecation reflex, is it in two parts as a short reflex, which involves peristalsis

in the colon and rectum relaxation of the internal anal sphincter and this is what

propels pieces through into the anus.

It's the long reflex which causes defecation to actually occur. So food entering

the the rectum will.

Stimulates the kind of sensors it will cause very strong peristaltic waves to occur

at the same time. Somebody is ready to defecate.

Then we get closure of the glottis get the valsalva maneuver occurs and abdominal

muscles will contract increases the intra-abdominal pressure.

The pelvic floor will descend and when the rectal pressure is greater than the pressure

across the anal sphincters and that will allow movement of feces through the anus.

This is controlled by the Pew bowrekt Alice muscle which normally it contracts to

choke the rectum or it can relax allowing the straightening of the rectum which

which allows the thesis to to exit.

So we normally produce about 150 grams of thesis today. It's largely composed of

water. So 2/3 of its water the remaining third is solid.

Total Transit time through the guts. It's between 10 and 68 hours.

So finally so motility isn't just when food is in the guts. We get those hunger

pangs when the gut is empty.

So in the presence of food, we're going to increase your nerve activity. We get

hormone release which causes an increase in motility. But in the absence of food,

we get something called a migrating motor cortex complex and this occurs from the

stomach fruit of the small intestine and it stimulated by a hormone called motility.

This is released from the duodenum the jejunum

and the my enteric plexus as well.

So the reason for these contractions there, they have some housekeeping functions.

So any large particulate so bits of bone shell anything that sort of entered the

stomach which it's got lodged there gets pushed through any epithelial cells old

epithelial cells release that needs replacing renewing they will gets left off.

They'll get passed through the

Testing and also it prevents bacteria in the colon from moving back into the small

intestine. So important function.

So these contractions so between meals and known as hunger pans.

disruption to this migrating Motor Court complex activity has been associated with

inflammatory, but

Irritable bowel syndrome obesity and also anorexia nervosa. So in summary gut motility

is regulated by the enteric nervous system. This is under the influence of the autonomic

nervous system, both sympathetic and parasympathetic the basic electrical rhythm

is composed of slow waves that importantly so these are induced by pacemaker cells

called the interstitial cells of kejal depolarization of these causes action.

From potential Spike essential to occur peristalsis can be induced by serotonin

which is released from the enter chromaffin cells.

And the various reflexes which will stimulate or inhibit movement of climb through

the small intestine. And these are on the hormonal and neural influence.