Exam 3 – Dr. Lunsford Gastric Secretions Flashcards
Describe countercurrent oxygen exchange
As much as 80% of blood oxygen diffuses directly from arterioles to venules before reaching the villus tips
What is gastrin secreted by?
G cells in response to proteins in the gastric lumen
What are the actions of gastrin?
Gastrin stimulates the secretion of histamine by enterochromaffin-like cells
Histamine acts on parietal cells stimulating acid secretion
What does increased gastrin lead to?
Increased gastric acid
What secretes gastric acid?
Parietal cells
How do you get a lot of gastrin?
When the kidney is not working properly
What is the hydrogen-potassium ATPase pump unique to?
Parietal cell
What does the hydrogen-potassium ATPase pump do?
Pumps hydrogen against a concentration gradient of 3 million to one
Where does the hydrogen-potassium ATPase pump exist?
Preformed in the cytoplasm of the cell until it is needed
When is the hydrogen-potassium ATPase pump transported to the cell membrane?
Upon stimulation of the parietal cell
What is the cephalic phase of gastric secretions?
The brains response to food
What causes the cephalic phase?
Sight of food
Smell of food
Thought of food
Taste of food
What causes the intensity of the cephalic phase to increase?
Appetite
What is the cephalic phase mediated by?
Neural signals that are transmitted by the vagus nerve
What are the neural signals that mediate the cephalic phase responsible for?
About 20% of gastric secretion
