Bsf Exam 5: Gi Secretions

Front 1

what are the substances that exocrine glands or secretory cells of the GI tract secrete into the GI lumen?

Back 1

digestive enzymes, mucus, HCL, water, electrolytes, intrinsic factor

Front 2

what are the three phases of GI secretion?

Back 2

cephalic, gastric and intestinal

Front 3

in what phase is food NOT in the GI tract?

Back 3

cephalic

Front 4

what reflex is associated with the cephalic phase?

Back 4

Pavlov's reflex

Front 5

what affect does parasympathetic simulation have on the rate of GI secretion?

Back 5

it increases it.

Front 6

what affect does sympathetic stimulation have on the rate of GI secretion? how does it do that?

Back 6

It has a dual effect: It may slightly increase secretion or it may decrease secretion if secretion is already increased by parasympathetic/hormonal stimulation. It is able to do that via vasoconstriction and reduction of blood supply.

Front 7

what are the GI hormones?

Back 7

gastrin, cck, secretin, GIP, and somatostatin

Front 8

what salivary gland(s) secretes only serous saliva?

Back 8

parotid

Front 9

what salivary gland(s) secrete both mucous and serous saliva?

Back 9

submandibular and sublingual

Front 10

which salivary gland(s) secretes only mucous saliva?

Back 10

buccal

Front 11

what two glands account for 90% of total secreted of salivary glands?

Back 11

parotid and mandibular.

Front 12

what are the five functions of saliva?

Back 12

lubrication, protection, hygiene, digestion and excretory

Front 13

what enzymatic component of saliva is a precursor for bradykinin, a strong vasodilator?

Back 13

kallikrein

Front 14

what are the three enzymes that are a part of the composition of saliva?

Back 14

ptyalin, lingual lipase, and kallikrein

Front 15

what Immunoglobulin is present in saliva?

Back 15

IgA

Front 16

Besides the main components of saliva (water, mucus, electrolytes), enzymes and immunoglobulins, what three categories of substances does saliva contain?

Back 16

bactericidal (lysozyme, lactoferrin),
blood group antigens, and
sex steroids (testosterone, estrogen and progesterone)

Front 17

*In regards to neutral pH, is the initial saliva hypertonic, isotonic, or hypotonic?

What are the primary secretions?

Back 17

isotonic


1. ptyalin, 2. mucus, 3. extracellular fluid

Front 18

before entering the oral cavity, in regards to neutral pH, does the saliva become hypertonic, isotonic or hypotonic? why?

Back 18

hypotonic; due to electrolyte modifications

NOTE: saliva is hypotonic to plasma at all flow rates

Front 19

along the striated duct that will produce saliva, two molecules are secreted and three molecules are reabsorbed. what are they?

Back 19

secreted: HCO3 and K
reabsorbed: Na, Cl, and water

Front 20

What affect does parasympathetic stimulation have on the rate of salivary secretion? sympathetic?

Back 20

they both increase.

Front 21

which stimulation is dominant, parasympathetic or sympathetic?

Back 21

parasympathetic

Front 22

Via what mechanisms does Parasympathetic stimulation affect salivation rate?

Back 22

via increased acinar and duct cell secretory activity and vasodilation

Front 23

what type of salivary secretion is secreted by the Parasympathetic Nervous system?

Back 23

copious, watery secretion

Front 24

what type of salivary secretion is secreted by the SNS (sympathetics)?

Back 24

thick, viscous secretion

Front 25

via what mechanisms does sympathetic stimulation affect salivation rate?

Back 25

via stimulation of myoepithelial cell contraction and causes vasoconstriction.

Front 26

Aldosterone causes an increase in secretion of _____ and an increase in reabsorption of ______.

Back 26

K+ and Na+

Front 27

?saliva osmolality and pH are partly determined by _____________ rate

Back 27

saliva secretion

Front 28

which molecule(s) in saliva has the highest resting composition? what is the value?

Back 28

K+; 70 mEq/L

*REALIZE higher in saliva than plasma
*however, as flow rate increases, drops slightly and then remains constant

Front 29

which molecule(s) in saliva has the lowest resting composition? what is the value?

Back 29

Cl- and Na+; 15 mEq/L

*REALIZE that these are lower in saliva than in plasma
*both increase as saliva flow rate increases, Na exponential (higher) & Cl linear

Front 30

which molecule(s) in saliva is right in the middle when in resting composition? what is the value?

Back 30

HCO3; 30 mEq/L

*REALIZE higher in saliva than plasma
*increases exponential w/ flow rate increase, but does not increase as much as Na

Front 31

what are the physiological stimulators for salivary sectreion? inhibitors?

Back 31

stimulators- conditioned (Pavlovian) reflexes: chewing, tasting, smelling, nausea

inhibitiors- sleep, fatigue, dehydration, fear

Front 32

what gland in the gastric mucosa produces HCl, pepsinogen, IF, and mucus?

Back 32

oxyntic gland*

parietal-HCL & IF
chief- pepsinogen
mucus- mucus

Front 33

what gland in the gastric mucosa produces mucus and gastrin?

Back 33

pyloric glands*

mucus- mucus
G cells- gastrin

Front 34

what section of the stomach contains oxyntic glands?

Back 34

fundus and body

Front 35

what section of the stomach contains pyloric glands?

Back 35

antrum

Front 36

what 6 things compose gastric juice?

Back 36

HCl, pepsinogen, gastric lipasem mucus, HCO3, and IF

Front 37

what are the functions of HCl?

Back 37

bactericidal (prevents GI infection), denature polypeptides, and it activates pepsinogen into pepsin

Front 38

what is the function of pepsinogen?

Back 38

pepsin initiates protein digestion

Front 39

what is the function of gastric lipase?


what is the function of IF?

Back 39

fat digestion


vitamin B12 absorption

Front 40

what are the functions of mucus and bicarb?

Back 40

lubricates chyme, the alkaline (pH =7) mucus layer is the gastric mucosal barrier, and buffers the gastric acid

Front 41

As the rate of gastric secretion increases, how are the following affected:
Cl-
H+
K+
Na+

Back 41

Cl-: increases exponentially, remains highest
H+: increases exponentially
K+: remains relatively constant
Na+: decreases exponentially *

Front 42

when does basal secretion occur in the stomach?

Back 42

when fasting

(lowest in morning, highest in evening, circadian)

pH 3-7

Front 43

what is the pH level of the stomach post-prandially? What 3 things does the pH depend on?

Back 43

pH< 1

1. gastric acid secreted
2. buffering power of food
3. rate of gastric emptying

Front 44

(post-prandial) stimulated secretion is stimulated by (3)? inhibited by (8)?


What are the phases?

Back 44

stimulated: Ach, gastrin, histamine

inhibited: somatostatin, secretin, CCK, peptide, YY, VIP, GIP, neurotensin

cephalic, GASTRIC, intestinal

Front 45

what is the neural stimuli for HCl (gastric acid) secretion?

Back 45

Parasympathetic nervous system - ach

(acts directly on parietal cells & indirectly by stimulating gastrin & histamine release)

Front 46

what is the paracrine stimuli for HCl secretion?


what is the endocrine stimuli for HCl secretion?

Back 46

histamine (direct)


Gastrin (direct & indirectly by stimulating histamine release)

Front 47

what enzyme is used to produce H and bicarb from CO2 and water?

(parietal cells)

Back 47

carbonic anhydrase

Front 48

How is H+ secretion via H/K ATPase pump regulated?

Back 48

increased activity of pump
--> increased H+ secretion
--> decreased activity of pump
--> decreased H+ secretion

Front 49

what four channels are involved in the secretion of HCl into the gastric lumen?

(parietal cells)

Back 49

H/K ATPASE, Na/K ATPase, HCO3/Cl- exchanger, Cl- channel

*all pumps on basal membrane except for H/K ATPase is on apical membrane

Front 50

which phase accounts for 20-30% of the total daily gastric secretion?

Back 50

cephalic phase

Front 51

What are the stimulatory signals of the cephalic phase?

Back 51

chewing & swallowing
taste, smell, & sight of food

Front 52

via what type of receptors do vagal afferent fibers relay impulses? where are these receptors located?

Back 52

via mechanoreceptors and chemoreceptors. located in the oral and nasal cavities

Front 53

T/F
efferent fibers increase acid secretion through direct and indirect mechanisms.

Back 53

true

Front 54

what is the direct mechanism for regulatory efferent pathways in the cephalic phase?

Back 54

vagal input to parietal cells mediated by ACh- most potent

Front 55

what is the indirect mechanism for regulatory efferent pathways in the cephalic phase?

Back 55

G cell stimulation of gastrin release mediated by GRP, histamine release by ECL cell

Front 56

which phase accounts for 60-70% of the total daily gastric secretion?

Back 56

gastric phase

Front 57

what are the stimulatory signals of the gastric phase?

Back 57

mechanically through the wall distention, chemically through partially digested protein products in chyme (AA and peptides) , calcium, caffeine and alcohol.

Front 58

what are the three regulatory pathways in the gastric phase?

Back 58

vago-vagal (extrinsic), local intramural (enteric NS) and G-cell stimulation

Front 59

What effect does eating have on acid secretion?

Back 59

-Ingested food buffers existing H+ and causes a drop in gastric H+
-In response the rate of H+ secretion rises
-As food leaves the stomach and the H+ concentration increases, the "interdigestive" level (of acidity) is achieved

Front 60

when is gastric secretion maximal?

Back 60

1 hour after a meal
(after buffering capacity of meal is saturated)

*once max is reached, it gradually begins to decrease as chyme enters duodenum

Front 61

what does high acidity of the stomach content inhibit? stimulate?

Back 61

inhibit: gastrin release (neg feedback)

stimulate: release of somatostatin (which directly inhibits secretion)

Front 62

what is the major inhibitory hormone that inhibits gastric acid secretion 1 hour after a meal?

Back 62

secretin
(anti-acid agent "AAA")

*its release is stimulated by chyme in duodenum

Front 63

what are the 5 stimuli for inhibitory hormones secretion?

Back 63

acids, protein digestion products, fat, hyperosmotic fluids, and hypoosmotic fluids = CHYME

Front 64

what reflex does the presence of food in the small intestine initiates? what is its function?

Back 64

a reverse enterogastric reflex that inhibits gastric secretion and stomach emptying

Front 65

which phase is only responsible for less than 10% of the total daily gastric secretion?

Back 65

intestinal

Front 66

what are the stimulatory signals for the intestinal phase? which one is the major stimulus?

Back 66

distention of the intestinal wall, circulating AA and protein digestion products in chyme (AA and peptides).
The major stimulus is circulating AAs.

Front 67

where do absorbed amino acids circulate in blood to during the intestinal phase?

Back 67

gastrin secreting cells (G-cell and parietal)

Front 68

what are the two regulatory pathways in the intestinal phase?

Back 68

gastrin and nervous mechanism

Front 69

**What are the MOST important inhibitors of bile acid (HCl) secretion?

Back 69

H/K-ATPase inhibitors

Front 70

What cells secrete pepsinogen

what stimulates pepsinogen secretion?
what increases pepsinogen secretion?

Back 70

Oxyntic glands secrete pepsinogen (duodenum & pyloric glands)

Ach (mainly via Vagal activation) and acid in the stomach lumen
secretin and gastrin

*pepsinogen---> pepsin (active)

Front 71

what layer lubricates chyme and buffers gastric acid?

Back 71

alkaline mucus layer --> gastric mucosal barrier

Front 72

what are 5 the protective factors on gastroduodenal mucosa?

Back 72

mucus, bicarb, prostaglandins, mucosal blood flow and growth factors

Front 73

what are the 7 damaging factors on gastroduodenal mucosa?

what leaks into the mucosa after a damaged mucosal barrier?

Back 73

H+, pepsin, H.pylori, NSAIDs, stress, smoking and alcohol.

H+ & pepsin

Front 74

what types of cells are damaged by leaking H+? what will that cause?

Back 74

mucosal mast cells --> stimulating release of histamine, platelet-activating factor, leukotrienes, endothelins, & thromboxane (vasoconstriction)

--> histamine acts on mucosal capillaries and causes local ischemia, hypoxia and vascular stasis.

Front 75

What does leaking pepsin cause?

Back 75

pepsin causes plasma proteins to leak into gastric lumen, resulting in bleeding

Front 76

what three factors contribute to peptic ulcer disease?

Back 76

H.pylori, NSAIDs, and Bile acid

Front 77

Via what three mechanisms does H.pylori damage the mucosa?

Back 77

1. produces NH4 and various cytokines,
2. increases H+ secretion
3. inhibits somatostatin secretion

Front 78

how do NSAIDs damage the mucosa?


how does bile acid damage the mucosa?

Back 78

by decreasing mucosal production of prostaglandins by inhibiting COX and causing mucosal damage

increase H+ leakage into the mucosa

Front 79

What do prostaglandins regulate?

Back 79

the secretion of mucus and bicarb

Front 80

where percentage of the pancreas is composed of exocrine cells?

Back 80

90%

Front 81

what comprises the aqueous component of the pancreas? what is the function of this component?

Back 81

bicarb, water and electrolytes; optimize pH for digestive enzymes and prevent ulceration

Front 82

what comprises the enzymatic component? via what cells?

Back 82

digestive enzymes: amylase, lipase and proteases. Via acinar cells

function= digestion

Front 83

what is the major hormone involved in the regulation of pancreatic secretion? what is the stimuli and primary effect?

Back 83

secretin. "nature's anti-acid"
stimuli: acidic (pH <4.5-5) chyme in duodenum.
primary: increased Bicarb from pancreas and liver

Front 84

what is the non major hormone involved in the regulation of pancreatic secretion? what is the stimuli and primary effect?

Back 84

CCK.
stimli: AA, some peptides, fatty acids in small intestine
primary: increase in enymes secretion

Front 85

what is the stimuli for pancreatic secretion under neural regulation (Ach)? what is the primary effect?

Back 85

stimuli: peptides, AAs
primary: increased enzyme secretion and increased aqueous secretion

Front 86

T/F
pancreatic enzyme secretion is able to adapt to the diet?

Back 86

true :)

Front 87

in a high protein, low carb diet, which one will increase: proteases or amylases?

Back 87

proteases

(decreases amylase)

Front 88

what potentiates the secretory responses to CCK and secretin & maintains normal rates of pancreatic protein synthesis & digestive enzymes?

Back 88

insulin

Front 89

where are the cells that secrete fluid and electrolytes into the intestinal lumen usually housed?

Back 89

in the crypts of the mucosa

Front 90

how many L/day are secreted in the small intestine?

What are the components in the secretion?

Back 90

1-2

electrolytes, ENZYMES, mucus, H20 (alkaline & isotonic)

Front 91

what are the functions of the intestinal secretion from the small intestine?

Back 91

chyme fluidity: digestion/absorption/motility, dilute toxins, and buffer

Front 92

what are the components of the secretion from the colon?

Back 92

mucus, K+ and bicarb
(secretes O.2 L/day)

Front 93

How is intestinal secretion in the colon regulated?

Back 93

Neural control (ENS & PNS)
-tactile (Mucosa)
-Distension (wall)
Hormonal (secretin-mucus secretion by Brunner's glands)

Front 94

T/F
composition of pancreatic juice is independent of the secretory flow rate.

Back 94

FALSE: the composition is dependent on the secretory flow rate