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GI > Gastric Motility and Pancreatic Function > Flashcards

Gastric Motility and Pancreatic Function Flashcards

1
Q

Purpose of Gut Motility

A
  1. Moving food from the mouth to the anus

2. Mechanical mixing of food, causing breakdown of larger molecules, increasing surface area for digestive enzymes.

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2
Q

Differentiate tonic and phasic contraction

A

Tonic: Sustained for minutes-hours. Occur in muscle spinchters and in the anterior portion of the stomach.

Phasic: Contraction/Relaxation cycles lasting a few seconds, occurs in the posterior aspect of the stomach and in the small intestine. Associated with slow-wave potentials.

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3
Q

Segmental vs Perstaltic Contraction

A

Segmental - Mixing

Peristalsis - Forward movement

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4
Q

Describe Segmental Contractions

A

Short 1-5cm segments of intestine alternatively contract and relax.

Circular muscle contracts while longitudinal muscle relaxes in the small intestine. Churning the luminal contents and keeping them in contact with the intestinal contents.

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5
Q

Describe Peristaltic Contraction

A

Progressive waves of contraction that moves food forward through the GI tract. Circular muscle contracts just behind the bolus and the circular muscle in front relaxes.

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6
Q

Gastric Peristaltic Waves

A

Travel through the stomach body to the antrum.

As the muscle in the body is thin, the contraction is weak in the body and does not contribute to mixing

In the Antrum the thick muscle, powerful contractions, mix the bolus.

The peristaltic wave continues to the pyloric sphincter

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7
Q

Affect of Peristaltic Waves on the Pyloric Sphincter

A

Contraction of the Sphincter allows some chyme to enter the duodenum, while forcing further mixing as the remaining chyme is forced back toward the body of the stomach.

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8
Q

Peristaltic Rhythm

A

Generated by pacemaker cells found in the longitudinal muscle layer every 3 mins to produce gastric peristaltic waves.

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9
Q

Slow Waves Rhythm/ Basic Electrical Rhythm

A

The basal or basic electrical rhythm (BER) the spontaneous depolarization and repolarization of pacemaker cells in the smooth muscle of the stomach, small intestine, and large intestine.

This electrical rhythm is spread through gap junctions in the smooth muscle of the GI tract

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10
Q

Neural/Hormonal Control of Motility

A

Gastrin -> increases contraction

Distension -> (stretch of stomach) –> increased contraction

Fat/Acid/Amino acid/ hypertonicity in the duodenum –> inhibit mobility.

Number of AP’s determine strength of contraction.

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11
Q

Does BER cause contraction in each slow-wave

A

Slow wave of depolarisation is below threshold and therefore will not contract. It requires further stimuli to reach action potential to induce contraction

.

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12
Q

Control of Strength of Contraction

A

When Stimuli is present, the strength of contraction is then determined by the number of AP’s triggered

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13
Q

How are gastric secretions neutralised in the duodenum

A

Bicarbonate is secreted from the brunner’s glands located in the submucosa.

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14
Q

What controls duodenal secretion of bicarbonate?

A

Acid in the duodenum triggers:

1) Long and Short reflexes triggering bicarbonate secretion
2) Release of Secretin from S cells from the pancreas and the liver

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15
Q

The reflexes of the nervous systems of the gut

A

Vagal - Long Reflexes

Enteric - Short Reflexes

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16
Q

Function of Secretin

A

Secretin stimulates the pancreas&bile duct to release bicarbonate.

17
Q

What inhibits secretin release?

A

Acid Neutralisation (negative feedback control)

18
Q

Components of the Pancreas

A 
Head - wrapped around the duodenum
Endocrine portion (bloodstream) - pancreatic islets, site of insulin production, glucagon, and somatostatin (enzyme controlling insulin/glucagon.

Exocrine portion (tubes) -acinar cells and lobules.

19
Q

Journey of Pancreatic Juice

A

Lobules ->intralobular ducts-> main pancreatic duct >common bile duct > hepatopancreatic ampulla (Sphincter of Oddi) duodenum

20
Q

Function of the Pancreas

A

Secretion of Bicarboate via duct cells

Secretion of digestive enyzymes via acinar cells

21
Q

Zygogens - definition and function and examples from the pancreas

A

The Pro digestive enzyme Trypsin is stored as zymogen granules= inactive moelcules (trypsinogen). To Prevent autodigestion of the pancreas.

Typrsingen is converted by enterokinases on the brush border of the duodenum

Trypsin can then convert other zymogens to active forms

22
Q

Function of Trypsin

A

Enterokinase Bound to the brush border of duodenal entreocytes, converts trysinogen to trypsin which then converts the other pancreatic enymes.

23
Q

Classes of Pancreatic Enzymes

A 
Proteases
Nucleases
Elastases
Phopholipidases - 
Lipases
A-amylase
24
Q

Function of Proteases

A

Cleave Peptide bonds

25
Q

Function of Nucleases

A

Hydrolyse DNA/RNA

26
Q

Function of elastases

A

collagen digestion

27
Q

Phopholipases

A

Phospholipids to fatty acids

28
Q

Lipases

A

Triglycerides to fatty acids glycerol

29
Q

a-amylase

A

Starch to maltose and glucose

30
Q

Function of the endocrine portion of the pancreas

A

Islets of Langerhans cells, pancreatic islets, produce insulin and glucagon, somatostatin (controls secretion insulin and glucagon)

31
Q

Function of exocrine portion portion

A

Acinar cells in the lobules. Acini feds–> through ducts–> Pancreatic duct.

Secretion of bicarbonate by duct cells. Secretion of digestive by acinar

32
Q

Origin and function of secretin. What triggers it’s release

A

Secretin - modulates pancreatic activity and is stimulated by S cells in the duodenum in response to acid in the duodenum. Stimulates release of bicarbonate.

33
Q

What stimulates release of zymogens?

A

Release of zymogens is stimulated by cholecystokinin

34
Q

What stimulates the release of CCK?

A

Cholecystokinin is released in response to fat/amino acids in the duodenum.

Release is also under neural control (long/short) reflexes triggered by arrival of organic nutrients in the duodenum

GI (20 decks)

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