QuestionSBA
QuestionChoice
This occurs in salivary duct cells, driven by the Na/K-ATPase. This process occurs to reduce sodium content in the saliva, allowing the glial-like cells of the taste buds to more sensitively detect dietary sodium.
10001222
b
Sodium is absorbed from the lumen by apical channels and sodium-proton exchangers and returned to the extracellular fluid
QuestionChoice
Driven by sodium gradients (into the cell, maintained by the Na/K-ATPase), basolateral NKCC1 brings chloride (alongside sodium and potassium) into salivary acinar cells. This creates a chloride concentration gradient from the cell into the lumen which chloride diffuses down via apical channels. This generates an electrochemical and osmolality gradient which results in the para-cellular flux of sodium and water into the lumen, generating saliva.
10001221
a
Chloride is actively secreted using basolateral NKCC1 and apical channels, resulting in passive sodium flux into the lumen
QuestionChoice
This occurs in pancreatic ducts, alkalinising secretions. The bicarbonate is generated by carbonic anhydrase from CO2 and water, and the proton is reabsorbed into the extracellular fluid by a sodium-proton exchanger while the chloride diffuses back into the lumen via apical channels.
10001224
d
Bicarbonate is generated in acinar cells and secreted in exchange for chloride by chloride-bicarbonate exchangers
QuestionChoice
This is part of the mechanism of gastric acid secretion by parietal cells. The bicarbonate is generated by carbonic anhydrase from CO2 and water, and the proton generated is secreted in exchange for potassium by a proton-potassium exchanger ATPase.
10001223
c
Chloride moves down its gradient from the extracellular fluid into cells using basolateral chloride-bicarbonate exchangers and diffuses into the lumen using apical channels
QuestionChoice
This describes some of the ion flux in the large intestine in which sodium and chloride are absorbed to draw water out of the faeces. Potassium may be re-secreted under the control of aldosterone depending on the plasma concentration.

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10001225
e
Sodium diffuses into cells from the lumen using ENaC and potassium exits (apical potassium channels) while chloride diffuses down a para-cellular concentration gradient
Concept
Chapter
2693
3805
Saliva
Topic
149
Gastro-intestinal physiology
12791
Which of the following describes the generation of ion gradients in the production of saliva by acinar cells?
a