Lecture 10 -Gastrointestinal Flashcards
(59 cards)
What are the control of gastric acid secretion?
Vagus: sight, smell, taste Release of gastric: presence of food (protein) Histamine CCK GIP Somatostatin
What is the PH in the stomach controlled by?
Gastric acid secretion
Why is secretion of HCL needed?
To get a low PH to get activation of relevant stomach enzymes (e.g. pepsin)
Why is carbonic anhydrase needed?
Generation of free H+ ions
What are the forms gastric secretion can take?
HCL Pepsinogen Mucus Bicarbonate ions
What is the acidic environment in the stomach maintained by?
Action of parietal cells
What do parietal cells do?
Secrete H+ against concentration gradient
Where does ATPase get hydrogen ions from?
Carbon dioxide and water
What are the bicarbonate ions exchanged for?
Chloride ions, the chloride ions will be transported along with K+ into gut lumen via a symporter mechanisms
When do peptic ulcers arise?
When the protective layer is disrupted Elevated prolonged acidity in the gut
What are the causes of peptic ulcer?
Stress: activation of vagus nerve NSAIDs: e.g. aspirin Diet: disrupt gut favouring breakdown and degradation of cell types within cell wall Alcohol Zollinger-Ellison Syndrome: tumour of cells tjat product gastric leading to altered HCL Bacterial: helicobacter
What may Helicobacter pylori be involved in?
Pathology of peptic ulcer
Why was it difficult to establish cultures?
Gut helicobacter pylori takes longer period to be established in the gut
What does G cell create?
Gastrin
What does gastrin interact with?
Cholecystokinin receptors to promote the release of local hormone histamine
What does histamine act upon?
Histamin receptor (H2) that stimulate the production of pumping of H+ ions in the target cell (parietal cells)
What does somatostatin regulate?
H+ ion level at many different sites at 3 different cell types
How may you be prone to stress ulcers?
Activation of the parasympathetic nerve system and the vagus nerve Elevation of ACH -> activate muscarinic receptors and cause reduction in HCL
What does prostaglandin receptor have negative effect on?
Histamine release
What is Aspirin mode of action?
Inhibit the enzyme that concert arachidonic acid into prostaglandin Inhibit enzyme: cyclooxygenase
What is Aspirin involved in?
Inflammatory pathways
What happens in the presence of Aspirin?
Prolonged and elevated secretions of H+ and formation of HCL in the gut which can lead/contribute to peptic ulcer
How can Aspirin contribute to peptic ulcer?
Manipulation of gastrin, enterochrokaffin-like, parietal cell axis
What are Antacids?
Medicines that counteract (neutralise) the acid in your stomach to relieve indigestion and heartburn
