Fan - Gut Motility

Question 1

Secondary esophageal peristalsis

Answer 1

When food gets stuck in the esophagus you begin a peristaltic wave just above where the food got stuck.

Question 2

How much time in various compartments?

Answer 2

Stomach - 2-4 hours
SI - 2-4 hours
- these two make up the digestive period

LI - 10-18 hours
- this makes up the interdigestive period

Swallowing - 10-15 seconds

Question 3

What are the anti-reflux mechanisms? Which do/don’t an infant or women have?

Answer 3

High LES tone - neither have this
Secondary esophageal peristalsis - woman still has this
Pinching of LES by the diaphragm - baby has this
Reflex (LES contracts in response to gastric and abdominal pressure increases) - neither have this

Question 4

What 4 things happen in the stomach during the digestive period?

Answer 4

Storage (upper stomach)
Mixing (lower stomach)
Size reduction (lower stomach)
Emptying

Question 5

How do ECAs work?

Answer 5

The stimulus is either the vagus nerve sensing distension of the stomach or Gastrin sensing peptides.

• This causes the activation of pacemaker cells in the stomach.
• This causes the contraction of muscle surrounding the stomach in a wave format all the way down to the pyloris.
• Once it gets to the bottom the pyloris and Antrim both contract at the same time, which grinds the food and then some is propulsed while whatever doesn’t fit gets repulsed back into the stomach. - called natural systole.
• Happens 3.7x per minute

Question 6

Why is it that we excreted significantly more water than we ingest?

Answer 6

gastric secretions

Question 7

Once the food has moved into the the SI what happens?

Answer 7

• acid from stomach stimulates the release of secretin.
• The FAs AAs and peptides stimulate the secretion of CCK
• glucose stimulates the secretion of GIP
• – all three of these then act to inhibit gastrin either directly or through somatostatin.
• – in addition, there are stretch receptors in the duodenum as well that tells the stomach not to put more food in the duodenum. Once the food passes, more food can go from the stomach into the duodenum.

Question 8

Migrating myoelectric Complexes

Answer 8

Intermittent contractions during the interdigestive period that are actually stronger than the consistent contractions that occur during the digestive period.

• pylorus stays open
• motilit is the mediator
• removes indigestible material and prevents bacterial overgrowth

Question 9

Why do we need a small pylorus. During the digestive period?

Answer 9

We don’t want emptying too fast.

- Dumping syndrome.

Question 10

What ions are involved in creating an ECA?

Answer 10

Depolarization - Na and Ca influx
Plateau - Na and Ca influx WITH K efflux
Repolarization - K efflux

Question 11

ERA

Answer 11

ECAs only cause muscle contraction when they reach threshold AND have spike potentials.

Question 12

Which neuroendocrines cause excitatory action in ECAs and which inhibitory?

Answer 12

As we mentioned earlier, Ach and Gastrin cause excitatory stimulation and will cause spike potentials to occur.
NE and NO will cause inhibitory action and will make an ECA less likely to occur.

• this was exhibited through an experiment in a beaker where not ECAs that reached threshold occurred without Ach. Once Ach was added, they occurred. Once it was washed off and NE was added, no ECAs that reached threshold occurred.

Question 13

How do the neuroendocrines affect peristalsis?

Answer 13

They exhibit their inhibitory affects on the forward piece of colon in order to make it relax and exert their excitatory affects on the piece behind in order to make it contract and move the bolus of food onward.
- The circular muscle is the part that will contract in order to move food forward, longitudinal muscle will do the opposite of whatever the circular muscle did.

Question 14

How is the neuroendocrine affect on peristalsis modulated?

Answer 14

As a bolus of food passes through the colon, it will activate baroreceptors, osmoreceptors, and chemoreceptors, which go to inter neurons in the smooth muscle and stimulate the ones in front to relax and the ones behind to contact.

Question 15

COntractile behaviors during:
Digestive
Interdigestive
Diarrhea

Answer 15

Digestive - you will have frequent, small contractions called segmentation
Interdigestive - uses MMCs to make large infrequent contractions
Diarrhea - there will be a lot of water excreted out into the colon, which induces the baroreceptors a lot and causes stretching of the colon.

Question 16

Stimulators reflexes

Answer 16

Gastroileal - entry of food into the stomach results in relaxation of the ileo-Cecil sphincter so that you can make room in the SI.
Gastrocolic - entry of food into the empty stomach or chyme into the duodenum results in increases in forward movement in the colon - to make room in the colon for the plus coming through.
Colonocolonic - distend one part of the colon and relax a later part in order to ensure forward movement.

Question 17

Inhibitory reflexes

Answer 17

Duodenogastric - duodenal distension causes decreases gastric emptying. - cause there is no room in the SI for the food from the stomach
Ileogastric - ileal distension leads to decreased gastric emptying -same reason as before.

Intestino-intestinal reflex - over-distention of a segment of intestine results in a generalized inhibition of intestinal muscle activity.
Conolic-intestinal reflex - over-distention in the colon resulting in a generalized inhibition of intestinal muscle activity.
Peritoneo-intestinal reflex - handling of peritoneum or after peritoneal irrigation results in generalized inhibition of intestinal muscle activity.