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Physiology II > L27: Salivary and Gastric Acid Secretions > Flashcards

L27: Salivary and Gastric Acid Secretions Flashcards

1
Q

What are the three main functions of saliva?

A

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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2
Q

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

A

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

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3
Q

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

A

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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4
Q

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

A

True

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5
Q

___ 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

A

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

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6
Q

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

A

1) Taste
2) Chewing

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7
Q

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

A

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

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8
Q

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

A

True

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9
Q

Where is the salivation reflex integrated?

A

Brainstem

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10
Q

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

A

False - increases both

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11
Q

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

A

Parasympathetic Nervous System

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12
Q

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

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

A

Parasympathetic
Sympathetic

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13
Q

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

A

False - decrease saliva production

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14
Q

Medications with which four features will DECREASE salivary production?

A

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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15
Q

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

A

Salivary flow rate

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16
Q

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

A

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

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17
Q

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

A

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

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18
Q

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

A

C. HCO3

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19
Q

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

A

B. Low salivary rates

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20
Q

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

A

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

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21
Q

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

A

False - there is LESS time

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22
Q

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

A

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

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23
Q

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

A

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

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24
Q

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

A

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

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25
Q

True or False: Aldosterone increases salivary flow rate

A

False - aldosterone does NOT change salivary flow rate

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26
Q

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

A

Mucins and Bicarbonate

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27
Q

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

A

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

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28
Q

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

A
  1. HCl (parietal cells)
  2. Pepsinogen (chief cells)
  3. Gastric Lipase (chief cells)
  4. Intrinsic Factors (parietal cells)
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29
Q

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

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

A

Pepsinogen: protein digestion
Gastric lipase: TG digestion

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30
Q

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

A

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

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31
Q

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

A

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

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32
Q

HCl is secreted by ___ cells of the gastric mucosal

A

parietal cells

33
Q

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

A

B. Apical Membrane

34
Q

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

A

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

35
Q

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

A

Exchanged for Cl- on the basolateral membrane

36
Q

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

A

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

37
Q

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

A

A. Apical membrane transporter

38
Q

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

A

Passive diffusion of water

39
Q

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

A

Availability of ATP for the H-K ATPase

40
Q
A
41
Q

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

A

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

42
Q

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

A

HCl

43
Q

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

A

True

44
Q

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

A

increase; Somatostatin; Prostaglandins

45
Q

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

A

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

46
Q

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

A

B. Hormone

47
Q

What are three function of gastrin secretion?

A

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)

48
Q

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

A

True

49
Q

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

A

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

50
Q

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

A

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

51
Q

Both GRP and Ach are released from ___ neurons

A

enteric

52
Q

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

A

False - short neural reflex only

53
Q

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

A

Long and short neural reflexes

54
Q

Which molecule DECREASES gastrin secretion from G cells?

A

Somatostatin

55
Q

Under which conditions is somatostatin released?

A

When pH is less than 3

56
Q

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

A

C. Paracrine

57
Q

Histamine stimulates the secretion of ___ and ___

Histamine inhibits the secretion of ___

A

HCl and Intrinsic Factor

Somatostatin

58
Q

____ and ___ increase histamine secretion

_____ decreases histamine secretion

A

Gastrin, Ach
Somatostatin

59
Q

Which cell secreted Histamine

A

ECL cells

60
Q

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

A

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

61
Q

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

A

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

62
Q

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

A

Ach; Histamine; decrease

63
Q

How does the pH of gastric contents alter somatostatin secretion?

A

pH of less than 3 = increases SS

pH of more than 3 = decrease SS

64
Q

Under what conditions is the vagus n activated?

A

While eating a meal

65
Q

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

A

Ach; cholinergic (Nn receptors)

66
Q

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

A

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

67
Q

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

A

Ach; HCl

68
Q

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

A

Ach and GRP

69
Q

True or False: Enteric neurons can release Ach and GRP

A

True

70
Q

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

A

somatostatin

71
Q

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

A

gastrin

72
Q

Histamine activates H2 receptors to directly ___ release of ___

Histamine activates H3 receptors to directly ___ release of ___

A

Increase; HCl
Decrease; somatostatin

73
Q

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

A

True

74
Q

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

A

distended; protein

75
Q

Which reflexes are activated by stomach distension?

A

Short neural reflexes
Long vagal reflexes

76
Q

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)

A

GRP; gastrin

77
Q

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

A

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)
78
Q

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

A

secretin

79
Q

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

A

True

Physiology II (23 decks)

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