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Physiology Flashcards

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1
Q

What are the 4 major functions of the GI Track

A
  1. Motility
  2. Secretion
  3. Digestion
  4. Absorption
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2
Q

What are the 3 ways in which peptides are delivered to their targets?

A
  1. Endocrine
  2. Paracrine
  3. Neurocrine
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3
Q

Gastrin

A

17 AA whose 4C terminal AA make up active cneter

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4
Q

Cholecstokinin

A

33AA closely related to gastrin structurally and functionally

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5
Q

Differences in activities in Gastrin & CCK

A

-depends on whether tyrosine is the 6th or 7th position from the C-terminus and whether or not it’s sulfated

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6
Q

GI Endocrine Cell

A

-hormone containing granules at the basal lateral membrane and the apical membrane adjacent to the gut lumen

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7
Q

VIP SIte of Release & Actions

A

Released: mucosa and smooth muscle of GI tract
Actions: relaxes sphincters
relaxes gut circular muscle
stimulates intestinal secretion
stimulates pancreatic secretion

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8
Q

Bombesin or GRP SIte of Release & Actions

A

Released: gastric mucosa
Actions: stimulates gastrin release

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9
Q

Enkephalins SIte of Release & Actions

A

Released: mucosa and smooth muscle of GI tract
Actions: inhibits intestinal secretion

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10
Q

Somatostatin

A

Action: inhibits gastrin release & other peptide hormone release
Site of release: GI mucosa, pancreatic islets
Releasers: acid, vagus inhibits release

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11
Q

Histamine

A

Action: stimulates acid secretion
Site of release: oxyntic gland mucosa ECL-cell
Releasers: gastrin, Ach

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12
Q

Gastrinoma: Zollinger-Ellison Syndrome

A
  • overproduction of gastrin
  • duodemal ulcer, diarrhea, steatorrhea
  • high rates of acid secretion
  • inactivation of pancreatic lipase
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13
Q

Pancreatic Cholera: Werner-Morison Syndrome

A
  • over production of VIP
  • diarrhea, metabolic acidosis, dehydration, hypokalemia
  • high rates of intestinal secretion
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14
Q

Gastric Esophageal Reflux Disease (GERD)

A
  • acid reflux
  • heartburn
  • hiatal hernia, pregnancy, failure of secondary peristalsis
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15
Q

Impaired Gastric Emptying

A
  1. Failure to empty
    • fullness, loss of appetite, nausea
    • obstruction-ulcer, cancer
    • vagotomy
  2. Increased Emptying
    • inadequate regulation
    • diarrhea, duodenal ulcer
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16
Q

GI Motility

A

Interaction of 3 neural network

  • central nervous system (CNS)
  • autonomic nervous system (ANS)
  • enteric nervous system
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17
Q

Enteric Nervous System

A

-neurons located in the gut wall comprise the intrinsic neural network, which is called the enteric nervous system

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18
Q

Other factors of GI Motility

A

-include neurotransmitters, neurohumoral factors-Serotonin, food and mechanical stretch

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19
Q

Autonomic Nervous System

A
  • both sympathetic and parasympathetic nervous system innervates GI tract
  • In General: sympathetic systems slows down GI motility, parasympathetic stimulates GI motility
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20
Q

Enteric Nervous System

A
  • present in the gut
  • comprises of 2 components
    1. myenteric plexus
    2. meissner plexus
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21
Q

Myenteric Plexus

A

-present b/w circular and longitudinal muscle layer

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22
Q

Meissner Plexus

A

-located in submucosa

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23
Q

Peristalsis

A
  • gut/intestinal contraction or peristalsis has rhythmicity
  • results from pacing from pacemaker present in ENS
  • pacemaker cells are interstitial cell of Cajal
  • Peristalsis results from a complex interaction b/w interstitial cell, other enteric neurons and smooth muscle
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24
Q

GI-Pacemaker Interstitial Cell of Cajal

A
  • interstitial cell are now thought to be pacemaker cell of GI tract
  • not neural in origin
  • they are present in Enteric nervous system
  • slow waves generates from these cell which lead to peristalsis at varialbe rate
  • present throughout GI tract
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25
Esophagus Motility
- conduit of solids/liquids to stomach - upper esophageal sphincter consist of striated muscle - body of esophagus has both striated and smooth muscle - lower esophageal sphincter (LES) let food pass through esophagus into the stomach - LES relaxation is controlled by vagus (NO, neurotransmitter)
26
Peristalsis in Esophagus
- primary: reflex esophageal peristaltic contraction wave associated with swallowing - secondary: residual food in the esophagus, as seen with ineffective peristalsis, may be cleared - tertiary: nonperistaltic contractions
27
Gastric Physiology
- receptive relaxation of fundus - upper - handles liquids - lower - solid pulverized - gastric pacemaker - 3 cycles/min - antrum empties contents in duodenum when particles size 1mm
28
Small Bowel Physiology
- facilitates nutrient absorption - organized motor pattern - motility pattern: fasting/fed pattern
29
Fasting Pattern/Migrating Motor Complex
-sweeping function/house keeping -four phases Phase 1: motor quiescence (40-60%) Phase 2: increasing but irregular contraction (20-30%) Phase 3: intense rhythmic contraction (20%) Phase 4: a transition from phase 3 to 1 (0-5%)
30
Fed Pattern
- following meal ingestion MMC converts in characteristic fed pattern - mixes and propel intestinal content
31
Achalasia
-greek meaning "doesn't relax" -esophageal motor disorder, failure of LES relaxation on swallow Treatment: sphincter dilatation with fish whale bone
32
Incidence & Etiology of Achalasia
- 1 in 100,000 - autoimmune, degenerative, infectious??? - selective loss of post-ganglionic inhibitory neurons (no NO) - Pathology: Lymphocyte infiltrate in myenteric plexus & loss of ganglion cells
33
Symptoms of Achalasia
- Dysphagia for solid (91%) and liquid (85%) - chest pain locating in area of xiphoid process in 40% - heart burn is reported in 40% - weight loss in 60% - regurgitation of food/Globus - association with adrenal insufficiency and alacrimin in children (Allgrove Syndrome)
34
Diagnosis of Achalasia
- history and physical - endoscopy - barium radiography - manometry
35
Endoscopy
- performed to evaluate condition that mimics Achalasia (pseudoachalasia) - dilated esophagus with food and pills - lower esophageal sphincter appear tight - examine gastro-esophgeal junction and fundus of stomach for any malignancy
36
Barium Swallow
- can be used as primary screening test (95% diagnostic accuracy) - dilated esophagus with bird beak appearance of distal part - severe dilation can lead to sigmoid esophagus - poor peristalsis on fluoroscopy
37
Manometry
- involves measurement of pressure using special catheter | - esophageal, antroduodenal and ano-rectal manometry are most common
38
2 Manometry Criteria to Diagnose Achalasia
- incomplete LES relaxation (LES fail to relax in response to swallow) - aperistalsis in the body of esophagus (distal 2/3) - supportive feature hypertensive LES, Low amplitude esophgeal contraction
39
Treatment of Achalasia
1. Medical: calcium blocker, nitrates 2. Endoscopic: Botulinum injection, balloon dilation 3. Surgery: heller's myotomy
40
Complications of Achalasia
- malnutrition - aspiration - malignancy: untreated achalasia is associated with an increased risk of squamous cell esophageal cancer
41
Diseases Associated with Achalasia-Like motility disorders
- malignancy, especially gastric carcinoma - Chagas Disease: secondary to Trypanosoma cruzi infection - Amyloidosis - Sarcoidosis - Neurofibromatosis
42
Motility Disorders Characterized by?
- heartburn, regurgitation, dysphagia | - chest pain
43
Abnormal Pattern Classified in what disorders?
- diffuse esophageal spasm - nutcracker esophagus - hypertensive lower esophageal sphincter
44
Diffuse Esophageal Spasm (Discoordinated Motility)
- repetitive contractions (>/= 3 peaks) | - prolonged duration contractions
45
Nutcracker Esophagus
hypercontracting esophagus | -increased distal peristaltic amplitude and duration
46
Motility
-movement of gut, propels food by smooth muscle
47
Secretion
-salivary glands, lining secrets mucus, acid from parital cells
48
Digestion
-neutrients, proximal small intestine
49
Serosal Surface
outside lining
50
Mucosa
inner lining
51
Endocrine
-release from one part, travels through blood stream, acts on another part of body
52
Paracrine
-acts on cells near their location that have a specific receptor
53
Neurocrine
-synthesized in cell body, migrate down axon and released by action potential
54
Effect of sulfination on gastrin?
no effect
55
Effect of sulfination on CCK?
-must have sulfate group, if not only has effects like gastrin does
56
2 Effects of CCK?`
1. stimulates gallbladder contraction | 2. stimulates pancreatic enzyme secretion
57
Receptor Gastrin acts on?
CCK-2 (B)
58
Receptor CCK acts on?
CCK-1 (A)
59
Why are all amino acids needed for activity of secretin family?
-because it exists in active form in a helical configuration so you need all amino acids to make the tertiary structure
60
Where is gastrin released from?
1. antrum 2. duodenum - also in jejunum
61
Where is CCK released from?
1. duodenum 2. jejunum 3. ileum
62
Where is Secretin released from?
1. duodenum | - also in jejunum and ileum
63
Where is GIP released from?
1. duodenum | 2. jejunum
64
Where is Motilin released from?
1. duodenum | 2. jejunum
65
What causes gastrin release?
protein, distention, nerve -inhibited by acid
66
What causes CCK release?
protein, fat
67
What causes Secretin release?
acid
68
What causes GIP release?
protein, fat, carbohydrates
69
What causes motilin release?
nerve
70
Actions of gastrin?
acid secretion | mucosal growth
71
Actions of CCK?
stimulates pancreatic HCO3- secretion pancreatic enzyme secretion gallbladder contraction pancreatic growth INHIBITS: gastric emptying
72
Actions of Secretin?
inc. pancreatic HCO3- secretion bile HCO33- secretion pancreatic growth INHIBITS: acid secretion
73
Actions of GIP?
insulin release (stimulates) INHIBITS: acid secretion
74
Actions of Motilin?
stimulates gastric motility | stimulates intestinal motility
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