Digestive System 3 Flashcards
What are Parietal Cells?
Parietal Cells Form hydrogen and bicarbonate from water and carbon dioxide
In the Parietal cell
What happens to the H+ once Carbonic Acid is broken down?
Hydrogen crosses into stomach lumen via primary active transport (hydrogen- potassium pump)
Apical Membrane
In the Parietal cell
What happens to the HCO3- (Bircarbonate) once Carbonic Acid is broken down?
Bicarbonate crosses into bloodstream and chloride crosses into parietal cell
(secondary active transport - counter transport)
Basolateral Membrane
In the Parietal cell
Once Chloride enters the Parietal Cell, where does it go?
Chloride flows into the stomach lumen via facilitated diffusion on the Apical Membrane
Once in the Stomach Lumen, what happens to Chloride?
The Hydrogen that left the parietal cell via primary active transport and the chloride that left the parietal cell via facilitated diffusion combine in the stomach lumen to form HCl
In the Parietal cell
What moves via facilitated transport?
K+ & Cl- on apical membrane
move in to stomach lumen
In the Parietal Cell
What moves via Primary Active Transport?
H+ and K+ via counter transport
H+ moves from Parietal cell to Stomach Lumen
K+ moves into Parietal Cell from Stomach Lumen
(On the Apical Membrane)
In the Parietal Cell
What moves via Secondary Active Trasnport?
HCO3- and Cl- via counter transport
HCO3- moves from Parietal Cell into Bloodstream
Cl- moves into Parietal Cell from Bloodstream
(On the Basolateral Membrane)
What Controls how much acid is released into the Stomach Lumen?
Secondary messengers regulate how many hydrogen-potassium pumps inserted on apical membrane.
What Increases Secondary Messengers?
(effectively increasing H+/K+ Pumps on Apical Membrane and releasing more acid)
Gastrin - Hormone
Histamine - Paracrine
Acetycholine (Ach) - Neurotransmitter
can release binded target cells to increase secondary messengers
gastrin (hormone), histamine (paracrine), and/or acetylcholine (neurotransmitter) are classified as what
Inhibitors (increase # of Secondary Messengers)
Which Hormone is Excitatory?
Somatostatin decrease the # of secondary messngers when target cells is released.
Resulting in less pumps on apical membrane and less acis in Lumen
Gastrin, Histamine and Acetycholine target cell release results in what?
increases secondary messengers
more pumps on apical membrane
more acid in lumen
What responds in both directions (pro-acid and anti-acid)?
chemoreceptors
What is Pro-Acid?
- Chemoreceptors detect a decrease in acidity
- Neural, Parasympathetic and Enteric work to increase acid formation
- Secretion of Gastrin (H), Histamine (P), Acetylcholine (NT)
- Increase in Secondary Messengers, Apical Pumps & Acid Formation
What is Anti-Acid?
- Chemoreceptors detect an increase in acidity
- Neural and Sympathetic work to decrease acid formation
- Secretion of Somatostatin (H)
- Decrease in Secondary Messengers, Apical Pumps & Acid Formation
- Negative Feedback
What is the negative feedback in the Anti Acid Response?
if acidity increases, gastrin won’t be released, meaning less secondary messengers
What is the Intestinal phase?
Intestinal phase – food arrives in duodenum –
receptors detect increased acidity, fats, amino
acids, distension