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GIT Flashcards

1
Q

Muscle fibers are electrically connected with one another allowing low resistance movement of ions from one muscle to the next

A

gap junction

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2
Q

When an AP is elicited anywhere within muscle, it generally travels in all directions

A

syncytium

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3
Q

Activity of GI smooth muscle

A

1 slow wave
2 spike

continual, slow, intrinsic electrical activity

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4
Q 
Rhythm determined by frequency 
Not action potentials 
Slow, undulating changes in RMP 
5-15 mv ; 3-12 freq per minute
3 in the stomach
12 in duodenum
8-9 in ileum
A

Slow wave

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5
Q

Electrical pacemakers for smooth muscle cells controlling slow waves

Undergo cyclic change in membrane potential due to unique ion channels that periodically open and produce inward (pacemaker) currents to generate slow wave

A

Interstitial cells of Cajal

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6
Q

Slow waves only cause contraction in

They mainly excite appearance of intermittent

A

stomach

Spike potentials that inturn actually excite ms contraction

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7
Q

True action potentials
Automatic when RMP of GI sm becomes more + (-50/-60 -> -40mv)
Each time peaks of slow waves become more + than -40, these appear

The higher the slow wave potential, the frequency becomes:

A

Spike potential

greater

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8
Q

AP of GI sm are

1
2

Than nerve fibers

A

longer 10-40x

run by calcium-sodium channels (slower to open and close) therefore longer AP

Ca ion is responsible for contraction

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9
Q

Cranial parasympathetic

A 
Mouth
Pharyngeal region
Esophagus
Stomach
Pancreas
First half of large intestine
-vagal
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10
Q

Sacral parasympathetic

A

2nd, 3rd, 4th sacral segment of spinal cord
Pelvic nerves
Distal half of large intestine to anus
-defecation

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11
Q

Postganglionic neurons of GI parasympathetic system are located in

A

myenteric and submucosal plexus

inc activity of entire enteric system

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12
Q

Depolarization of membrane is triggered by

A

1 stretching of muscle
2 stimulation by acetylcholine from parasympathetic nerves
3 stimulation by GI hormone

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13
Q

Hyperpolarization of membrane is caused by

A

1 NE and Epi on fiber membrane

2 sympathetic nerve stimulation by NE

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14
Q

Slow waves are propelled by these ions

A

sodium

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15
Q

Spike potentials from slow wave are generated by these ions

A

calcium

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16
Q

Continuous, lasting minutes to hours increasing or dec in intensity but still continues
Caused by continuous repetitive spike potentials or hormones that bring about continuous partial depolarization of smooth muscle without action potential
Calcium entry without change in membrane potential

A

Tonic contraction

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17
Q

Outer plexus between longitudinal and circular ms layer

Controls mainly GI movement

A

Myenteric Auerbach’s plexus

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18
Q

In submucosa
Inner plexus
Controls mainly GI secretion and local blood flow

A

Submucosal meissner’s plexus

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19
Q

Myenteric Auerbach’s plexus generate

A

1 inc tonic contraction
2 inc intensity of rhythmical contraction
3 inc rate of rhythm of contraction
4 inc velocity of conduction of excitatory waves (peristaltic)

But not entirely excitatory bec has inhibitory fxn through transmitter

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20
Q

Inhibitory trasmitter secreted by Myenteric Auerbach’s

A

Vasoactive intestinal peptide

Act on the pyloric and ileocecal valve

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21
Q

Submucosal Meissner’s plexus regulates

A

1 secretion
2 absorption
3 contraction
of submucosal muscle (infolding)

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22
Q

Excites GI activity

A

acetylcholine

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23
Q

Inhibits GI activity

A

norepinephrine

epinephrine

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24
Q

Neural control of gut (3)

A

1 post sympathetic/pre paraganglionic
2 enteric
3 sensory (to enteric the prevertebral ganglia and spinal cord)

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25
Sympathetic fibers run from
``` T5-L2 Preganglionic fibers enter sympathetic chain lateral to spinal column Celiac ganglion, mesenteric ganglia Post ganglionic sympathetic neurons Secrete NE and EPI ```
26
Afferent sensory fibers are stimulated by
1 irritation of mucosa 2 distention of gut 3 specific chemical substances in gut
27
80% of vagal nerve fibers are
afferent
28
GI reflexes (3)
1 integrated within gut wall enteric NS (secretion, peristalsis, mixing, contraction) 2 gut to prevertebral sympa and back to GI (gastrocolic, enterogastric, colonoileal) 3 from gut to spinal cord and brain stem and back to GI (pain, gastric moror and secretion, defacation)
29
Signal from stomach cause evacuation of colon
Gastrocolic reflex
30
Signal from colon and SI to inhibit stomach motility and secretion
Enterogastric reflex
31
Colon to inhibit emptying of ileal content to colon
Colonoileal reflex
32
Secreted by G cells in antrum, duodenum, jejenum Stimulated by protein, distention, nerve Inhibited by acid
Gastrin
33
Gastrin stimulates
gastric acid secretion | mucosal growth
34
Secreted by I cells of duodenum, jejunum, and ileum | Stimulated by protein, fat and acid (proteoses, peptone and long chain FA
Cholecystokinin
35
CKK stimulates inhibits
pancreatic bicarbonate secretion pancreatic enzyme secretion gallbladder contraction growth of exocrine pancreas gastric emptying
36
Secreted by S cells of duodenum, jejunum and ileum | Stimulated by acid and fat
Secretin
37
Secretin stimulates Inhibits
pepsin secretion pancreatic bicarbonate secretion biliary bicarbonate secretion growth of exocrine pancreas gastric acid secretion
38
Secreted by K cells of duodenum and jejunum | Stimulated by protein, fat and carbohydrate
Gastric inhibitory peptide
39
Gastric inhibitory peptide stimulates Inhibits
insulin release gastric acid secretion
40
Secreted by M cells of duodenum and jejunum during fasting Stimulated by fat, acid and nerve
Motilin
41
Motilin stimulates
gastric motility interdigestive myoelectric complexes intestinal motility
42
Types of movements of GI tract
1 propulsive forward food movement | 2 mixing
43
Contractile ring around the gut that moves anything in front forward Stimulus:
Peristalsis distention of gut chemical and physical irritation parasympathetic signals
44
Law of gut
Peristaltic reflex to anal direction of movement | Receptive relaxation propelling food toward anus
45
Kinins released that promote vasodilation
Kallidin Bradykinin Adenosine
46
Stages of swallowing
1 voluntary 2 pharyngeal 3 esopahgeal
47
Control of stomach emptying resides in
1 inhibitory feedback signals from duodenum (enterogastric) | 2 CCK
48
Gastric empyting is slowed by
1 too much chyme is already in small intestine 2 chyme is acidic 3 too much fat or hypertonic or hypotonic 4 irritating
49
Hormones that promote peristalsis in intestine
``` gastrin CCK insulin motilin serotonin ```
50
hormones that inhibit small intestinal motility
secretin | glucagon
51
Single celled, secrete mucus in response to irritation of epithelium and act as lubricant to protect surface from excotiation and digestion
Mucus goblet glands
52
Invagination of epithelium into mucosa | Deep, contain secretory cell
pits | crypts of Lieberkuhn
53
Acid and pepsinogen secreting gland of stomach and upper duodenum
Oxyntic gland | Tubular
54
Secretion of glands is stimulated by
1 tactile stimulation 2 chemical irritation 3 distention of gut wall
55
Sympathetic effect on glandular secretion (2)
1 slightly inc secretion | 2 superimposed sympa on para significantly reduces secretion bec of vasoconstrictive reduction of blood supply
56
Basic Mechanism of secretion
1 diffusion of nutrient material or active transport to capillary into base of gland 2 oxidative energy ATP from mitochondria utilized by gland 3 synthesis of secretory substance from ATP and substrate in ER and golgi 4 formation of proteins in secretion by ribosome 5 transport of secretion from ER to golgi (20 mins) 6 modification, concentration and discharge of secretion into cytoplasm in form of secretory vesicle in apical end 7 vesicle storage until use (inc in cell membrane perm by control signal to calcium, ca entry causing vesicle fusion with apical membrane -> exocytosis
57
Daily secretion of saliva Saliva contains large amounts of ions
800-1500 ml K (acini primary secretion along with ptyalin) and bicarbonate (duct by passive exchange of bicarbonate for chloride) sodium chloride conc are several times less in saliva than in plasma Net result: under resting conditions, NaCl conc is about 15 meq/L while K is at 30 meq/L bicarbonate at 50-70 meq/L
58
Saliva two types of protein
1 ptyalin - serous, alpha amylase for starch dig | 2 mucin - mucus for lubrication and protection
59
Parotid glands secrete While submandib and sublingual secrete Buccal glands secrete Saliva pH
serous secretions both serous and mucus mucus only 6-7 favorable for ptyalin
60
Saliva contains enzymes that destroy bacteria
1 lysozyme -attacks bacteria 2 thiocyanate ions - bactericidal, digest and help remove bacteria support 3 antibody
61
Primary secretion Secondary secretion
Ptyalin Mucus ECF Na active absorption Cl passive absorption K active secretion HCO3 secretion
62
Secrete HCl Pepsinogen Intrinsic factor Mucus On the body and fundus 80% proximally
Oxyntic | Gastric glands
63
Secrete mucus for protection of stomach mucosa and gastrin Located on antrum 20% distal
Pyloric glands
64
Stomach oxyntic gland cell and secretion
1 mucous neck cell : mucus 2 chief cell : pepsinogen 3 parietal oxyntic : HCl and intrinsic factor
65
Factors that stimulate gastric secretion
``` 1 acetylcholine (excites pepsinogen, mucus and hydrochloric acid secretion) 2 gastrin (HCl) 3 histamine (HCl) ```
66
Along with secretion of HCl parietal oxyntic cells also secrete this for VitB12 cobalamin absorption
Intrinsic factor Absorption in ileum
67
ECL cells in recess of oxyntic glands release this in relation to the rate and amt of formation of HCl stimulated by gastrin
Histamine
68
When protein reaches antrum, this hormone is released by G cells and is then transported in the blood to ECL to release histamine
Gastrin
69
Pepsinogen secretion is mediated by
1 stimulation of chief cells by acetylcholine from vagus or enteric nerve 2 in response to gastric acid
70
Hormones in the SI that inhibit gastric secretion
Secretin GIP (GDIP) VIP Somatostatin
71
Pancreatic enzymes digest all three major type of food. Most important are:
1 trypsin, chymotrypsin and carboxypolypeptidase for protein, peptides and AA 2 lipase for fatty acid and monogly 3 cholesterol esterase for hydrolysis 4 phospholipase for FA from phospholipid
72
Trypsinogen is activated by
Enterokinase | Trypsin from activated trypsinogen
73
Pancreas also secrete copious amounts of this ion to neutralize gastric acid
bicarbonate
74
Acetylcholine and cholecystokinin stimulate meanwhile secretin stimulates
Large quantities of pancreatic enzyme but small water and electrolytes secretion of water rich sodium bicarbonate soln
75
Secretin causes copious secretion of While CKK causes secretion of
pancreatic fluid water and bicarbonate also in the second part of bile secretion pancreatic enzyme
76
Bile amount Functions
600-1000ml 1 bile salt emulsify fat particles into minute particles for lipase 2 absorption of digested fat end product 3 excretion of waste bilirubin and cholesterol
77
Bile is concentrated by
Na Absorption and secondary chloride ion and water absorption
78
Bile salt formation
Cholesterol -> cholic and chenodeoxycholic acid Acids combine with glycine and taurine -> glyco and tauroconjugates bile acid Sodium salt secreted in bile
79
Compound mucus glands in the wall of duodenum secreting large amounts of alkaline mucus in resp to tactile or irritation and vagal stimulation and secretin Inhibited by
Brunner’s gland of duodenum pH 8 - 8.9 sympathetic stimulation
80
Crypts of Lieberkuhn in small intestine secrete
Watery fluid rich in Cl and bicarbonate creating sodium solute drag and osmotic movement of water
81
Digestive enzyme in small intestines
``` 1 peptidase (AA) 2 sucrase, maltase, isomaltase, lactase (disach to monosach) 3 lipase (fat into glycerol and FA) ```
82
Regulation of small intestine secretion unlike the rest of the GI is through
local enteric nervous reflex
83
Protein fat and carbohydrate digestion mostly takes place in the
Small intestine
84
Fructose is absorbed in the small instestine by Glucose is absorbed by
facilitated diffusion Na-glucose co transport
85
Indole Skatole Mercaptan Hydrogen sulfide
Odoriferous products
86
H pylori promotes stomach ulceration by
Burrowing into the gastric barrier | Producing ammonia that liquefies barrier and stimulates secretion of HCl digesting wall
87
Factors that inc mucosal ulceration
1 excess secretion of gastric juice esp initial portion of duodenum 2 smoking 3 alcohol 4 aspirin NSAID
88
Gluten destroys and blunts microvilli dec absorptive mucosa of twofolds when eating rye or wheat
Nontropical sprue Celiac disease Idiopathic sprue Gluten enteropathy
89
Inflammation of intestinal mucosa from unidentified infectious agent occuring in tropics
Tropical sprue
90
Sprue complication
1 steatorrhea 2 severe nutritional def, wasting 3 osteomalacia bec of lack of Ca 4 inadequate blood coagulation bec of lack of Vit K 5 macrocytic anemia bec of B12 and folic acid
91
Hirschprung’s disease results from lack of
ganglion cell in myenteric Auerbach’s plexus
92
``` Antiperistalsis Deep breath Raising of hyoid bone and larnyx to pull up esophageal sphincter open Closing of glottis Lifting of soft palate to close nares Contraction of diaphragm LES relaxation ```
Vomiting act
93
The liver receives percentage of CO Pressure into the portal vein leading into liver is
27% 9mmHg indicating low resistance inc if cirrhotic -> from fibrosis
94
Promotes liver regeneration Inhibits liver
HGF EDGF TNF IL6 TGFB
95
Liver role in protein metabolism
Deamination of amino acid Formation of urea for excretion of ammonia Forming plasma protein Conversion of AA to other compounds (nonessential AA)
96
Vitamin stored in sufficient quantity in liver
A D (good for 3-4 m) B12 (at least 1 yr)
97
Test that differentiates unconjugated from conjugated bilirubin
Van den Bergh and | Negative urobilinogen in urine (obstructing jaundice)
98
Acetylcholine to gastric contraction
Stimulates
99
Gastrin to gastric contractions
Gastrin
100
Norepinephrine to gastric contractions
inhibits
101
Gastric emptying is slowest after a meal rich in
Fats
102
Factors that lead to increase emptying
Gastrin
103
Forceful retching Hematemesis Alcoholic
Mallory-Weis Tear in the GEJ
104
Increasing the intraabdomunal pressure against a closer glottis is otherwise known as:
Valsalva maneuver
105
Location of CTZ
Roof of the fourth ventricle Area postrema Medulla oblongata
106
Highly specific and selective serotonin 5HT3 receptor antagonist the nerve terminals of vagus peripherally and centrally in CTZ arew postrema Low affinity for dopamine receptors
Ondansentron
107
Inhibits D2 and serotonin 5 HT3 receptors in CTZ Administration leads to prokinetic effects via inhibitory actions on presynaptic and postsynaptic D2 receptora Agonism of 5HT4 Antagonism of muscarinjc receptor inhibition Enhances releae of acetylcholine, inc LES ang gastric tone accelerating gastric emptying
Metaclopromide
108
Most of the length of small intestine is from the
Ileum
109
In the duodenum secrete copious amounts of HCO3
Brunner’s glands
110
Emetogenic drugs such as chemotherapeutic agents promote vomiting by
Release of serotonin from the enterochromaffin cells of small intestine by causing degenerative changes of GI tract Serotonin stimulates the vagal and splanchnic nerve receptors that project to medullary vomiting centers as well as the serotonin receptors in the area postrema thus initiating the vomiting reflex causinf nausea and vomiting
111
Splanchnic blood flow receives
about 25% of cardiac output
112
Blood from GI does not flow directly to IVC because it is shunted to
portal system
113
Contain secretory granules that release regulatory peptides and amines to hell regulate GI function
Enteroendocrine cells
114
Dopamine exerts this effect on GI tract
relaxant
115
Most frequent movement of SI
segmentation
116
Resection of this portion of the gut leads to impaired RBC maturation
Ileum t
117
Mucous neck cell secretes
Mucous
118
Parietal cells secrete
HCl
119
Chief cells secrete
Pepsinogen
120
Enterochromaffin cells secrete
Serotonin | Substance P
121
Enterochromaffin cells Kulchitsky cells produce
Serotonin
122
Enterochromaffin-like cells produce
``` Histamine Chromogranin A (Pancreastatin) ```
123
Destruction of parietal cells as seen in chronic gastritis is accompanied by decreased production of HCl and
Intrinsic factor
124
Pepsinogen maximal activity
pH 2.0
125
Pepsinogen inactivated at
pH 6.5
126
Pepsinogen is activated by
Zymogen HCl Acid pH
127
RBC production is defective caused by autoimmune attack against parietal cells
Pernicious anemia
128
Control of gastric acid secretion 3 physiologic agonists
Histamine Ach Gastrin
129
Elicit release of histamine from ECL cells
Gastrin
130
Endogenous antagonist to acid secretion
Somatostatin Prostaglandin E Prostaglandlin I Epidermal growth factor
131
The stomach secretes about
2 L of gastric juice
132
Most important of pancreatic enzymes for digesting proteins are
Trypsin Chymotrypsin Carboxypeptidase
133
Secreted by I cells Stimulated by fats and protein Promotes pancreatic enzyme secretion Promotes pancreatic bicarbonate Causes contraction of gallbladder -> release of bile
Cholecystokinin
134
Especially when fatty foods reach the duodenum after this long post meal
30 minutes

Physiology (23 decks)

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