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Physiology > GIT > Flashcards

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
Q

Sympathetic fibers run from

A 
T5-L2
Preganglionic fibers enter sympathetic chain lateral to spinal column
Celiac ganglion, mesenteric ganglia
Post ganglionic sympathetic neurons 
Secrete NE and EPI
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26
Q

Afferent sensory fibers are stimulated by

A

1 irritation of mucosa
2 distention of gut
3 specific chemical substances in gut

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27
Q

80% of vagal nerve fibers are

A

afferent

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28
Q

GI reflexes (3)

A

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)

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29
Q

Signal from stomach cause evacuation of colon

A

Gastrocolic reflex

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30
Q

Signal from colon and SI to inhibit stomach motility and secretion

A

Enterogastric reflex

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31
Q

Colon to inhibit emptying of ileal content to colon

A

Colonoileal reflex

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32
Q

Secreted by G cells in antrum, duodenum, jejenum
Stimulated by protein, distention, nerve
Inhibited by acid

A

Gastrin

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33
Q

Gastrin stimulates

A

gastric acid secretion

mucosal growth

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34
Q

Secreted by I cells of duodenum, jejunum, and ileum

Stimulated by protein, fat and acid (proteoses, peptone and long chain FA

A

Cholecystokinin

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35
Q

CKK stimulates

inhibits

A

pancreatic bicarbonate secretion
pancreatic enzyme secretion
gallbladder contraction
growth of exocrine pancreas

gastric emptying

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36
Q

Secreted by S cells of duodenum, jejunum and ileum

Stimulated by acid and fat

A

Secretin

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37
Q

Secretin stimulates

Inhibits

A

pepsin secretion
pancreatic bicarbonate secretion
biliary bicarbonate secretion
growth of exocrine pancreas

gastric acid secretion

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38
Q

Secreted by K cells of duodenum and jejunum

Stimulated by protein, fat and carbohydrate

A

Gastric inhibitory peptide

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39
Q

Gastric inhibitory peptide stimulates

Inhibits

A

insulin release

gastric acid secretion

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40
Q

Secreted by M cells of duodenum and jejunum during fasting

Stimulated by fat, acid and nerve

A

Motilin

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41
Q

Motilin stimulates

A

gastric motility
interdigestive myoelectric complexes
intestinal motility

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42
Q

Types of movements of GI tract

A

1 propulsive forward food movement

2 mixing

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43
Q

Contractile ring around the gut that moves anything in front forward

Stimulus:

A

Peristalsis

distention of gut
chemical and physical irritation
parasympathetic signals

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44
Q

Law of gut

A

Peristaltic reflex to anal direction of movement

Receptive relaxation propelling food toward anus

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45
Q

Kinins released that promote vasodilation

A

Kallidin
Bradykinin

Adenosine

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46
Q

Stages of swallowing

A

1 voluntary
2 pharyngeal
3 esopahgeal

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47
Q

Control of stomach emptying resides in

A

1 inhibitory feedback signals from duodenum (enterogastric)

2 CCK

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48
Q

Gastric empyting is slowed by

A

1 too much chyme is already in small intestine
2 chyme is acidic
3 too much fat or hypertonic or hypotonic
4 irritating

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49
Q

Hormones that promote peristalsis in intestine

A 
gastrin
CCK
insulin
motilin
serotonin
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50
Q

hormones that inhibit small intestinal motility

A

secretin

glucagon

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51
Q

Single celled, secrete mucus in response to irritation of epithelium and act as lubricant to protect surface from excotiation and digestion

A

Mucus goblet glands

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52
Q

Invagination of epithelium into mucosa

Deep, contain secretory cell

A

pits

crypts of Lieberkuhn

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53
Q

Acid and pepsinogen secreting gland of stomach and upper duodenum

A

Oxyntic gland

Tubular

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54
Q

Secretion of glands is stimulated by

A

1 tactile stimulation
2 chemical irritation
3 distention of gut wall

55
Q

Sympathetic effect on glandular secretion (2)

A

1 slightly inc secretion

2 superimposed sympa on para significantly reduces secretion bec of vasoconstrictive reduction of blood supply

56
Q

Basic Mechanism of secretion

A

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
Q

Daily secretion of saliva

Saliva contains large amounts of ions

A

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
Q

Saliva two types of protein

A

1 ptyalin - serous, alpha amylase for starch dig

2 mucin - mucus for lubrication and protection

59
Q

Parotid glands secrete

While submandib and sublingual secrete

Buccal glands secrete

Saliva pH

A

serous secretions

both serous and mucus

mucus only

6-7 favorable for ptyalin

60
Q

Saliva contains enzymes that destroy bacteria

A

1 lysozyme -attacks bacteria
2 thiocyanate ions - bactericidal, digest and help remove bacteria support
3 antibody

61
Q

Primary secretion

Secondary secretion

A

Ptyalin
Mucus
ECF

Na active absorption
Cl passive absorption
K active secretion
HCO3 secretion

62
Q

Secrete HCl
Pepsinogen
Intrinsic factor
Mucus

On the body and fundus 80% proximally

A

Oxyntic

Gastric glands

63
Q

Secrete mucus for protection of stomach mucosa and gastrin

Located on antrum 20% distal

A

Pyloric glands

64
Q

Stomach oxyntic gland cell and secretion

A

1 mucous neck cell : mucus
2 chief cell : pepsinogen
3 parietal oxyntic : HCl and intrinsic factor

65
Q

Factors that stimulate gastric secretion

A 
1 acetylcholine (excites pepsinogen, mucus and hydrochloric acid secretion)
2 gastrin (HCl)
3 histamine (HCl)
66
Q

Along with secretion of HCl parietal oxyntic cells also secrete this for VitB12 cobalamin absorption

A

Intrinsic factor

Absorption in ileum

67
Q

ECL cells in recess of oxyntic glands release this in relation to the rate and amt of formation of HCl stimulated by gastrin

A

Histamine

68
Q

When protein reaches antrum, this hormone is released by G cells and is then transported in the blood to ECL to release histamine

A

Gastrin

69
Q

Pepsinogen secretion is mediated by

A

1 stimulation of chief cells by acetylcholine from vagus or enteric nerve
2 in response to gastric acid

70
Q

Hormones in the SI that inhibit gastric secretion

A

Secretin
GIP (GDIP)
VIP
Somatostatin

71
Q

Pancreatic enzymes digest all three major type of food. Most important are:

A

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
Q

Trypsinogen is activated by

A

Enterokinase

Trypsin from activated trypsinogen

73
Q

Pancreas also secrete copious amounts of this ion to neutralize gastric acid

A

bicarbonate

74
Q

Acetylcholine and cholecystokinin stimulate

meanwhile secretin stimulates

A

Large quantities of pancreatic enzyme but small water and electrolytes

secretion of water rich sodium bicarbonate soln

75
Q

Secretin causes copious secretion of

While

CKK causes secretion of

A

pancreatic fluid water and bicarbonate also in the second part of bile secretion

pancreatic enzyme

76
Q

Bile amount

Functions

A

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
Q

Bile is concentrated by

A

Na Absorption and secondary chloride ion and water absorption

78
Q

Bile salt formation

A

Cholesterol -> cholic and chenodeoxycholic acid
Acids combine with glycine and taurine -> glyco and tauroconjugates bile acid
Sodium salt secreted in bile

79
Q

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

A

Brunner’s gland of duodenum

pH 8 - 8.9

sympathetic stimulation

80
Q

Crypts of Lieberkuhn in small intestine secrete

A

Watery fluid rich in Cl and bicarbonate creating sodium solute drag and osmotic movement of water

81
Q

Digestive enzyme in small intestines

A 
1 peptidase (AA)
2 sucrase, maltase, isomaltase, lactase (disach to monosach)
3 lipase (fat into glycerol and FA)
82
Q

Regulation of small intestine secretion unlike the rest of the GI is through

A

local enteric nervous reflex

83
Q

Protein fat and carbohydrate digestion mostly takes place in the

A

Small intestine

84
Q

Fructose is absorbed in the small instestine by

Glucose is absorbed by

A

facilitated diffusion

Na-glucose co transport

85
Q

Indole
Skatole
Mercaptan
Hydrogen sulfide

A

Odoriferous products

86
Q

H pylori promotes stomach ulceration by

A

Burrowing into the gastric barrier

Producing ammonia that liquefies barrier and stimulates secretion of HCl digesting wall

87
Q

Factors that inc mucosal ulceration

A

1 excess secretion of gastric juice esp initial portion of duodenum
2 smoking
3 alcohol
4 aspirin NSAID

88
Q

Gluten destroys and blunts microvilli dec absorptive mucosa of twofolds when eating rye or wheat

A

Nontropical sprue
Celiac disease
Idiopathic sprue
Gluten enteropathy

89
Q

Inflammation of intestinal mucosa from unidentified infectious agent occuring in tropics

A

Tropical sprue

90
Q

Sprue complication

A

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
Q

Hirschprung’s disease results from lack of

A

ganglion cell in myenteric Auerbach’s plexus

92
Q 
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
A

Vomiting act

93
Q

The liver receives percentage of CO

Pressure into the portal vein leading into liver is

A

27%

9mmHg indicating low resistance
inc if cirrhotic -> from fibrosis

94
Q

Promotes liver regeneration

Inhibits liver

A

HGF
EDGF
TNF
IL6

TGFB

95
Q

Liver role in protein metabolism

A

Deamination of amino acid
Formation of urea for excretion of ammonia
Forming plasma protein
Conversion of AA to other compounds (nonessential AA)

96
Q

Vitamin stored in sufficient quantity in liver

A

A
D (good for 3-4 m)
B12 (at least 1 yr)

97
Q

Test that differentiates unconjugated from conjugated bilirubin

A

Van den Bergh and

Negative urobilinogen in urine (obstructing jaundice)

98
Q

Acetylcholine to gastric contraction

A

Stimulates

99
Q

Gastrin to gastric contractions

A

Gastrin

100
Q

Norepinephrine to gastric contractions

A

inhibits

101
Q

Gastric emptying is slowest after a meal rich in

A

Fats

102
Q

Factors that lead to increase emptying

A

Gastrin

103
Q

Forceful retching
Hematemesis
Alcoholic

A

Mallory-Weis Tear in the GEJ

104
Q

Increasing the intraabdomunal pressure against a closer glottis is otherwise known as:

A

Valsalva maneuver

105
Q

Location of CTZ

A

Roof of the fourth ventricle
Area postrema
Medulla oblongata

106
Q

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

A

Ondansentron

107
Q

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

A

Metaclopromide

108
Q

Most of the length of small intestine is from the

A

Ileum

109
Q

In the duodenum secrete copious amounts of HCO3

A

Brunner’s glands

110
Q

Emetogenic drugs such as chemotherapeutic agents promote vomiting by

A

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
Q

Splanchnic blood flow receives

A

about 25% of cardiac output

112
Q

Blood from GI does not flow directly to IVC because it is shunted to

A

portal system

113
Q

Contain secretory granules that release regulatory peptides and amines to hell regulate GI function

A

Enteroendocrine cells

114
Q

Dopamine exerts this effect on GI tract

A

relaxant

115
Q

Most frequent movement of SI

A

segmentation

116
Q

Resection of this portion of the gut leads to impaired RBC maturation

A

Ileum t

117
Q

Mucous neck cell secretes

A

Mucous

118
Q

Parietal cells secrete

A

HCl

119
Q

Chief cells secrete

A

Pepsinogen

120
Q

Enterochromaffin cells secrete

A

Serotonin

Substance P

121
Q

Enterochromaffin cells Kulchitsky cells produce

A

Serotonin

122
Q

Enterochromaffin-like cells produce

A 
Histamine
Chromogranin A (Pancreastatin)
123
Q

Destruction of parietal cells as seen in chronic gastritis is accompanied by decreased production of HCl and

A

Intrinsic factor

124
Q

Pepsinogen maximal activity

A

pH 2.0

125
Q

Pepsinogen inactivated at

A

pH 6.5

126
Q

Pepsinogen is activated by

A

Zymogen HCl Acid pH

127
Q

RBC production is defective caused by autoimmune attack against parietal cells

A

Pernicious anemia

128
Q

Control of gastric acid secretion

3 physiologic agonists

A

Histamine
Ach
Gastrin

129
Q

Elicit release of histamine from ECL cells

A

Gastrin

130
Q

Endogenous antagonist to acid secretion

A

Somatostatin
Prostaglandin E Prostaglandlin I
Epidermal growth factor

131
Q

The stomach secretes about

A

2 L of gastric juice

132
Q

Most important of pancreatic enzymes for digesting proteins are

A

Trypsin
Chymotrypsin
Carboxypeptidase

133
Q

Secreted by I cells

Stimulated by fats and protein

Promotes pancreatic enzyme secretion

Promotes pancreatic bicarbonate

Causes contraction of gallbladder -> release of bile

A

Cholecystokinin

134
Q

Especially when fatty foods reach the duodenum after this long post meal

A

30 minutes

Physiology (23 decks)

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