Secretions Of The GI Tract & Pancreas-1/22/16

Question 1

___ cells of the salivary gland secrete initial saliva

When stimulated by neural input, ____ cells contract to eject saliva into the mouth

The ___ duct contains myoepithelial cells and saliva in this duct is similar in ionic composition to plasma

Answer 1

Acinar

Myoepithelial

Intercalated duct

Question 2

The ___ duct is lined by columnar epithelial cells and modify the initial saliva to produce the final saliva that is HYPOTONIC

Answer 2

Striated

Question 3

___ is a protease involved in the production of bradykinin (vasodilator)

Answer 3

Kallikrein

Question 4

The formation of isotonic, plasma-like saliva is done by ___ cells

The modification of this isotonic solution is later done by the ___ cells

Answer 4

Acinar

Ductal

Question 5

In the mechanism of salivary secretion, ___ is secreted into the lumen and ____ is reabsorbed into the bloodstream

Answer 5

HCO3 and K are secreted

Na and Cl are reabsorbed

Question 6

List the transporters on the luminal (apical) membrane for salivary secretion/reabsorption

Answer 6

Na-H exchanger (Na reabsorbed, H secreted)
Cl-HCO3 exchanger (Cl reabsorbed, HCO3 secreted)
H-K exchanger (H reabsorbed, K secreted

Question 7

Patients with cystic fibrosis have a defect in this channel:

Answer 7

Cyclic AMP-activated CFTR channel (secretes both Cl and HCO3)

Question 8

How does saliva become hypotonic as it flows through the ducts?

Answer 8

Ductal cells are impermeable to water

Question 9

At decreased flow rates, final saliva has lower concentration(s) of ___ and higher concentration(s) of ___

Answer 9

Na and Cl

K

Question 10

What ganglion does the pre-synaptic fibers of the facial nerve synapse on? Where does the post-synaptic fiber travel to for synapsing?

Answer 10

Pre-ganglionic travels on Facial Nerve and synapses on Submandibular ganglion –> Post ganglionic travels and synapses on both Submandibular and Sublingual glands

Question 11

What ganglion does the parasympathetic pre-synaptic fibers of the glossopharyngeal nerve synapse on? Where do the post-ganglionic fibers synapse?

Answer 11

Preganglionic travels on Glossopharyngeal nerve and synapses on Otic Ganglion –> Post-ganglionic synapses on parotid gland

Question 12

Preganglionic sympathetic nerves originate at the ___, whose postganglionic fibers extend to the glands in the ____ spaces

Answer 12

cervical ganglion

Periarterial

Question 13

What effect does conditioning, food, nausea, and smell have on parasympathetic innervation for salivary secretion?

What effect does fatigue, dehydration, fear, and sleep have on parasympathetic innervation for salivary secretion?

Answer 13

Stimulatory

Inhibitory

Question 14

The blood supplied to the salivary glands is distributed by branches of the ____ artery

Answer 14

Branches of the external carotid

Question 15

What are the main components of gastric juice?

Answer 15

HCl (H+)
Pepsinogen
Mucus
IF
Water

Question 16

___, together with pepsin, initiates the process of protein digestion and is necessary for the conversion of pepsinogen to pepsin

Answer 16

HCl (H+)

Question 17

____, together with HCO3, neutralizes acid and maintains the surface of the mucosa at a neutral pH

Answer 17

Mucus

Question 18

___ is required for the absorption of vitamin B12 in the ileum

Answer 18

Intrinsic Factor

Question 19

The ____ gland is located in the proximal 80% of the stomach (body and fundus) and secretes acid

The ____ gland is located in the distal 20% of the stomach (antrum) and synthesizes and releases gastrin

Answer 19

Oxyntic

Pyloric

Question 20

The result of the cellular mechanism by gastric parietal cells is net secretion of ___ and net absorption of ___

Answer 20

HCl

HCO3-

Question 21

___ is released from ECL cells in the gastric mucosa and stimulates HCl secretion.

Answer 21

Histamine

Question 22

Histamine binds to ___ receptors on parietal cells and its action can be blocked by this drug: ____

Answer 22

H2

Cimetidine

Question 23

Binding of histamine to H2 receptors leads to a 2nd messenger cascade via ___ that ultimately results in secretion of H+ through _____ ATPase

Answer 23

Cyclic AMP

H+/K+

Question 24

___ is released from the vagus nerve innervating the gastric mucosa and stimulates HCl secretion.

Answer 24

Ach

Question 25

Ach binds to ___ receptors leading to this ____ 2nd messenger cascade that ultimately results in secretion of H+ via the ____ ATPase

Answer 25

M3 mAChRs IP3/Ca2+ H+/K+

Question 26

Ach can have an indirect effect on HCl secretion through stimulation of ___ Cells, which release histamine

Answer 26

ECL

Question 27

___ is secreted into circulation by G cells in the antrum and delivered back to the stomach via the circulation. It stimulates HCl secretion

Answer 27

Gastrin

Question 28

Gastrin binds to ____ receptors on parietal cells and binding to these receptors leads to this ___ second messenger cascade that ultimately results in the secretion of H+ through the ___ ATPase

Answer 28

CCKb IP3/Ca2+ H+/K+

Question 29

___ is released from delta cells (mostly located in the antrum) and inhibit HCl secretion

Answer 29

Somatostatin

Question 30

Somatostatin binds to ___ receptors on parietal cells and binding results in inhibition of ____ that ultimately results in inhibition of secretion of H+ (direct pathway)

Answer 30

Somatostatin receptor type 2 (SSTR2) Adenylate cyclase

Question 31

In the indirect pathway, somatostatin inhibits ____

Answer 31

Both histamine release from ECL cells and gastrin release from G cells

Question 32

___ can potentiate the actions of Ach and Gastrin ___ can potentiate the actions of histamine and gastrin

Answer 32

Histamine Ach

Question 33

What drug is an antagonist of H2 receptors that blocks that action of histamine and potentiated effects of Ach and gastrin? What drug is an antagonist of mAChR's that blocks the direct effects of Ach and Ach-potentiated effects of histamine and gastrin?

Answer 33

Cimetidine Atropine

Question 34

___ inhibits the H+/K+ ATPase on gastric parietal cells and is used to treat ulcers to reduce H+ secretion

Answer 34

Omeprazole

Question 35

List the 3 phases of Gastric HCl secretion

Answer 35

Cephalic (30%) Gastric (60%) Intestinal (10%)

Question 36

List the 2 mechanims of the cephalic phase of gastric HCl secretion

Answer 36

Vagus n. --> Parietal cell: innervation releasing Ach to parietal cells, Ach stimulates secretion of HCl from parietal cells Vagus n. --> gastrin --> parietal cell: innervation releasing Gastrin-releasing peptide (GRP) to G cells, G cells release gastrin into circulation, gastrin is delivered back to stomach to stimulate HCl secretion from parietal cells (VAGOTOMY ABOLISHES THIS PHASE)

Question 37

What are stimuli of the gastric phase of Gastric HCl secretion?

Answer 37

Distention of stomach and presence of breakdown of proteins, AAs, and small peptides Distention activates mechanoreceptors in the mucosa of both oxyntic and pyloric glands

Question 38

Describe the mechanism of Distention of Antrum of the Gastric phase of Gastric HCl secretion

Answer 38

Distention of antrum --> local reflex (pyloropyloric reflex) --> gastrin --> parietal cells --> HCl

Question 39

At low secretion rates, final gastric juice is essentially a solution of ____ At higher secretion rates, the concentration of Na+ ___ and that of H+ ____ At peak rates, gastric juice is primarily ____

Answer 39

NaCl decreases, increases HCl

Question 40

Regarding gastric juice, the concentration of H, K, Cl are ___ than those in plasma, and the concentration of Na is ___ than that in plasma

Answer 40

Higher Lower

Question 41

Non-parietal gastric juice secretions have a basal ___ secretion of constant and low volume and its primary constituents are ____

Answer 41

Alkaline Na and Cl; K is present at the same concentration as in plasma

Question 42

Parietal gastric juice secretion is slightly ___-osmotic and ___ is the only anion present

Answer 42

Hyper Cl

Question 43

Regarding the regulation of gastrin release, ___ stimulates gastrin release while ___ acts on G cells to inhibit gastrin release

Answer 43

GRP Somatostatin

Question 44

Vagal activation stimulates gastrin release by releasing ___ and inhibiting release of ___

Answer 44

GRP Somatostatin

Question 45

How is gastrin regulated/inhibited?

Answer 45

Negative feedback regulation by gastrin (gastrin itself increases somatostatin) H+ in the lumen of the stomach stimulate release of somatostatin

Question 46

___ is secreted by chief and mucus cells in the oxyntic glands and ____ stimulation is the most important stimulus for its secretion

Answer 46

Pepsinogen Vagus nerve

Question 47

In order for pepsinogen to be converted to pepsin, what is required?

Answer 47

H+ secretion from parietal cells to lower pH of gastric contents (pH H+ triggers local cholinergic reflexes that stimulate chief cells to secrete pepsinogen

Question 48

What is the optimal pH range of pepsin? When is it reversibly inactivated? When is it irreversibly inactivated?

Answer 48

Optimal=1.8-3.5 Reversibly inactivated= >5.0 Irreversibly inactivated= >7-8

Question 49

Failure of Parietal cells to secrete IF may lead to ___

Answer 49

Pernicious anemia

Question 50

List protective components of gastric mucosa List damaging components to gastric mucosa

Answer 50

Protective=HCO3, mucus, PG's, mucosal blood flow, and growth factors Damaging=Acid, pepsin, NSAIDs, H pylori, aspirin, alcohol, bile, and stress

Question 51

___ forms primarily because the mucosal barrier is defective and the major causative agent is H pylori A diagnostic test of this peptic ulcer disease is based on __ activity

Answer 51

Gastric ulcers Urease

Question 52

___ forms because H+ secretory rates are higher than normal and role of H pylori is indirect

Answer 52

Duodenal ulcers

Question 53

Zollinger-Ellison syndrome is associated with ___ ulcers. It is usually a tumor in the pancreas that secretes large quantities of ___

Answer 53

Duodenal Gastrin

Question 54

What are the 2 main components of the exocrine pancreas secretion?

Answer 54

Aqueous solution containing HCO3 | Enzymatic secretion

Question 55

___ activity stimulates pancreatic secretion and ____ activity inhibits pancreatic secretion

Answer 55

Parasympathetic | Sympathetic

Question 56

Pancreatic amylases and lipases are secreted as ___ enzymes by acinar cells and pancreatic proteases are secreted in inactive forms and converted to their active forms in the ___

Answer 56

Active lumen of the duodenum

Question 57

____ cells produce the initial aqueous solution from the pancreatic secretions which is isotonic and contains Na, K, Cl, and HCO3. The initial secretion is then modified by transport processes in the ____ cells

Answer 57

Centroacinar and ductal Ductal epithelial

Question 58

After modification of initial pancreatic secretion by ductal cells, the net result is secretion of ___ into the pancreatic ductal juice and net absorption of ___

Answer 58

HCO3 H+

Question 59

At increased flow rate, what are concentration of HCO3 and Cl in the pancreatic juice? At decreased flow rate, what concentrations of HCO3 and Cl in the pancreatic juice?

Answer 59

HCO3=highest, Cl=lowest HCO3=lowest, Cl=highest

Question 60

Which phase of pancreatic secretion accounts for 80% of pancreatic secretion and is regarded as the most important phase?

Answer 60

Intestinal-Both enzymatic and aqueous secretions are stimulated