L27: Salivary and Gastric Acid Secretions Flashcards by Katlyn Heneghan

What are the three main functions of saliva?

1) Secrete R Protein - Vit B12 absorption

2) Initiate digestion of carbohydrates (a-amylase)

3) Neutralize H+ in distal esophagus (HCO3)

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How does aldosterone secretion affect the absorption of Na by ductal cells? How does it effect the rate of salivary secretion?

Aldosterone
- Increase absorption of Na by ductal cells
-Does NOT change rate of salivary secretion

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True or False: The enteric nervous system controls the rate of salivary secretion

False - the rate of salivary secretion is under neural control via: parasympathetic and sympathetic nervous system.

The rate of salivary secretion is NOT under hormonal control

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True or False: Prior to even taking first bite of food, seeing and smelling the food leads to salivary secretion

True

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___ is the weakest stimulus of salivary secretion
A. Taste
B. Smell
C. Sight
D. Feeling

___ is the most potent stimulus of salivary secretion
A. Taste
B. Smell
C. Sight
D. Feeling

B. Smell (least potent)
A. Taste (most potent)

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While eating a meal, salivation reflex is initiated by ___ and the mechanical act of ____

1) Taste
2) Chewing

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Acidic taste is the ____ taste stimulant while sweet tase is the ___ taste stimulant

Acidic taste = strongest taste stimulant
Sweet taste = weakest taste stimulant

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True of False: Receptors in the oral mucosa, muscles of mastication, and temporomandibular joint are activated s/p chewing

True

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Where is the salivation reflex integrated?

Brainstem

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True or False: The salivation reflex decreases both parasympathetic and sympathetic nerve activity

False - increases both

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Which is more physiologically important for the salivation reflex: the sympathetic nervous system or the parasympathetic nervous system?

Parasympathetic Nervous System

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___ stimulation causes a sustained, high volume secretion of watery saliva

____ stimulation causes a transient, low-volume secretion of thick, viscous saliva

Parasympathetic
Sympathetic

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True or False: Dehydration and Sjogren’s Syndrome increase saliva production

False - decrease saliva production

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Medications with which four features will DECREASE salivary production?

1) Interact with pancreatic acinar muscarinic receptors
2) Reduce blood flow to salivary gland
3) Interfere with sodium transport
4) Modify autonomic efferent nerve activity to salivary glands

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What is the electrolyte composition of the final salivary secretion closely linked to?

Salivary flow rate

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True or False: The final salivary secretion is hypertonic at all flow rates

False - the final salivary secretion is hypotonic at all flow rates

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True or False: The concentration of sodium in saliva is always higher than the concentration of sodium in the plasma

False - the concentration of sodium in saliva is always LOWER than the concentration of sodium in the plasma

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At all flow rates, secretion of which molecule is high in the salivary duct?
A. Na+
B. K+
C. HCO3
D. Aldosterone

C. HCO3

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Under what conditions do ductal cells reabsorb most of the NaCl (due to having more time for absorption)?
A. High salivary rates
B. Low salivary rates

B. Low salivary rates

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How does a low salivary rate affect the concentration of NaCl, HCO3, and K+ in the final salivary secretion?

[NaCl] = low
[HCO3] and [K] = high

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True or False: At extremely high flow rates there is MORE time for NaCl to be reabsorbed by ductal cells

False - there is LESS time

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How would you expect the concentrations of NaCl, HCO3, and K to be affected by high flow rate?

[NaCl] and [HCO3] = high
[K] = low

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How would you expect the final salivary concentrations of NaCl, HCO3, and K to be affected by high flow rate?

[NaCl] and [HCO3] = high
[K] = low

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How can aldosterone modify the electrolyte concentration of the final salivary secretion?

-Increasing the ductal Na reabsorption
-Increasing ductal cell K+ secretion

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True or False: Aldosterone increases salivary flow rate

False - aldosterone does NOT change salivary flow rate

What two gastric substances are secreted by enterocytes to protect the stomach lining?

Mucins and Bicarbonate

What are three hormone/paracrine substances that are secreted by the gastric mucosa to modulate HCl secretion?

1) Gastrin (G cells) 2) Histamine (ECL cells) 3) Somatostatin (D Cells)

Which four substances are secreted by the gastric mucosa to aid in food digestion?

1. HCl (parietal cells) 2. Pepsinogen (chief cells) 3. Gastric Lipase (chief cells) 4. Intrinsic Factors (parietal cells)

____ is secreted by the chief cell and is responsible for protein digestion _____ is secreted by the chief cell and is responsible for TG digestion

Pepsinogen: protein digestion Gastric lipase: TG digestion

Which cell secreted intrinsic factor? What is Intrinsic Factor important for?

The Parietal Cells secrete Intrinsic Factor - Intrinsic Factor is required for B12 absorption

What are four reasons that HCl secretion by Parietal Cells is helpful to the human body?

1) Denatures proteins in food 2) Kills ingested bacteria 3) Dissolves CT in food 4) Maintains low pH for pepsin activty

HCl is secreted by ___ cells of the gastric mucosal

parietal cells

Which membranes of the parietal cell contains a H-K ATPase proton pump that actively transports K+ into the cell and H out of the cell? A. Basolateral Membrane B. Apical Membrane

B. Apical Membrane

Where does the H+ that is ultimately pumped out of the parietal cell by the H-K ATPase proton pump come from?

CO2+H2O combine inside the parietal cell, leads to production of H+ and HCO3 (via: CA)

What happens to the excess HCO3 produced in the parietal cell as a result of CO2 combining with H2O?

Exchanged for Cl- on the basolateral membrane

How does the exchange of excess intracellular HCO3 with Cl- at the basolateral membrane affect the pH of the gastric venous blood?

As bicarbonate enters venous circulation, pH of gastric venous blood increases

How does Cl- leave the parietal cell? A. Apical membrane transporter B. Basolateral membrane transporter

A. Apical membrane transporter

What follows secretion of H and Cl (HCl) from the parietal cell?

Passive diffusion of water

What is the rate limiting step of HCl secretion from parietal cells?

Availability of ATP for the H-K ATPase

True or False: Parietal cells have many receptors located on their apical membranes that, when activated, can directly decrease HCl secretion

False - parietal cells have many receptors located on their basolateral membranes that, when activated, can directly increase HCl secretion

In the absence of parietal cell basolateral receptors agonist, the secretion of ___ is limited

HCl

True or False: The actions of parietal cell receptor agonists are synergistic

True

Histamine ____ generation of cAMP while_____ and ____ decrease generation of cAMP

increase; Somatostatin; Prostaglandins

True or False: When activated, somatostatin receptors on basolateral membranes of parietal cells increase generation of cAMP

False - when activated, somatostatin receptors on basolateral membranes of parietal cells DECREASE generation of cAMP

What type of molecule is gastrin? A. Peptide B. Hormone C. Steroid

B. Hormone

What are three function of gastrin secretion?

1) Increase secretion of HCl, intrinsic factor, and histamine 2) Stimulate growth of gastric mucosa (trophic hormone) 3) Promotes mass movements in colon (gastrocolonic reflex)

True or False: Like parietal cells and D cells, G cells have receptors located on their basolateral membranes that, when activated, increase or decrease gastrin secretion

True

How do protein digestion product in the gastric lumen increase gastrin secretion?

Protein digestion products in the gastric lumen activate GRP-releasing IPAN's to increase gastrin secretion

What are four factors that increase gastrin secretion from G cells?

1) GRP - gastrin releasing peptide 2) Ach 3) Protein digestion products in the gastric lumen 4) Strong gastric distension

Both GRP and Ach are released from ___ neurons

enteric

True or False: Protein digestion products in the gastric lumen are associated with long and short neural reflexes

False - short neural reflex only

Strong gastric distension is associated with which type of neural reflexes?

Long and short neural reflexes

Which molecule DECREASES gastrin secretion from G cells?

Somatostatin

Under which conditions is somatostatin released?

When pH is less than 3

What type of molecule is histamine? A. Endocrine B. Hormone C. Paracrine

C. Paracrine

Histamine stimulates the secretion of ___ and ___ Histamine inhibits the secretion of ___

HCl and Intrinsic Factor Somatostatin

____ and ___ increase histamine secretion _____ decreases histamine secretion

Gastrin, Ach Somatostatin

Which cell secreted Histamine

ECL cells

Cytoplasmic processes of the D cell directly contact __, ___ and ___ cells, allow for locally release somatastatin to tonically inhibit the secretion of which three molecules?

Parietal (HCl) G cell (gastrin) ECL cell (histmaine)

How does decreasing somatostatin secretion affect HCl, gastrin, and histamine secretion?

Decreasing somatostatin secretion removes its TONIC INHIBITION, and allows for increased HCl, Gastrin, and Histamine secretion

D cells have receptors located on their basolateral membranes for __and __ that, when activated, ____ somatostatin secretion

Ach; Histamine; decrease

How does the pH of gastric contents alter somatostatin secretion?

pH of less than 3 = increases SS pH of more than 3 = decrease SS

Under what conditions is the vagus n activated?

While eating a meal

When vagus n is activated, ___ is released and binds to ___ receptors on enteric neurons

Ach; cholinergic (Nn receptors)

How is the activation of enteric neurons, the release of gastrin/somatostatin/HCl affected by activation of vagus n?

Vagus n activation leads to: 1) Activation of enteric neurons 2) Increase gastrin release 3) Increased HCl secretion 4) Suppression of Somatostatin

Enteric neurons release ___, which activates muscarinic receptors to directly increase release of __ from parietal cells

Ach; HCl

___ and ___, released by enteric neurons, directly stimulate release of gastrin from G cells

Ach and GRP

True or False: Enteric neurons can release Ach and GRP

True

Ach, released by enteric neurons, directly inhibits the release of ____ from D cells

somatostatin

When parasympathetic vagus nerve is activated, ___ travels in the plasma to directly increase the release of histamine (ECL cells) and HCl (parietal cells)

gastrin

Histamine activates H2 receptors to directly ___ release of ___ Histamine activates H3 receptors to directly ___ release of ___

Increase; HCl Decrease; somatostatin

True or False: A pH that is lower than 3 in the gastric lumen will increase the release of somatostatin from D cells

True

As food is swallowed and enters the stomach, the gastric smooth muscle becomes ____, digestion of dietary __ starts, and H+ is buffered

distended; protein

Which reflexes are activated by stomach distension?

Short neural reflexes Long vagal reflexes

Protein digestion products, as when there is food in the stomach, increases ___ release from enteric neurons to increase ___ release from G cells (short neural reflex)

GRP; gastrin

How does a pH that is greater than 3 in the gastric lumen affect release of somatostatin from D cells?

Decreased release of somatostatin from D cells - Lower mucosal somatostatin results in a) increase in release of gastrin (G cells), histamine (ECL) and HCl (Parietal)

When chyme enters the duodenum, the low pH in the duodenal lumen stimulates the release of ____ from endocrine cells in the small intestinal mucosa

secretin

True or False: Secretin inhibits H+ secretion by acting at receptors located on parietal cells (negative inhibition)

True