pharmacology Flashcards
What do mucus cells secret in the gastric crypt?
- bicarbonate
- mucus
What do parietal cells secret in the gastric crypt?
- hydrochloric acid
What do enterochromaffin-like cells secrete in the gastric crypt?
- histamine
What do G cells secrete in the gastric crypt?
- gastrin
What do D cells secrete in the gastric crypt?
- somatostatin
What do chief cells secrete in the gastric crypt?
- pepsinogen
What does histamine bind to?
- Histamine H2 receptors in the gastric lumen
- subsequent activation of adenylyl cyclase
What causes the release of histamine by enterochromaffin-like cells?
- stimulation by acetylcholine
What happens to the number of protons pumps when histamine binds to H2 receptors?
- activation of adenylyl cylase
- increase in cAMP
- increases number of proton pumps increasing gastric acid secretion
What is ACh released by?
- parasympathetic cholinergic neurons
what does ACh bind to on parietal cells?
- binds to muscarinic (M3) ACh cells receptors
What happens with an increase in intracellular Ca2+?
- evokes cell signalling pathways
- increases number of proton pumps
- increases gastric acid secretion from parietal cells
What does gastrin bind to on parietal cells?
- CCK2 receptors
- causes an increase in intracellular Ca2+ levels
What does somatostatin bind to and what does it cause?
- binds to SST2R receptors
- inhibits adenylyl cyclase
What affect does somatostatin have on the levels of cAMP?
- decreases cAMP
- Decreases gastric acid secretion from parietal cells
What affects do antacids has and how do they achieve this?
- reduce the symptoms of excessive gastric secretion by buffering HCl
- buffering system
Name 2 examples of antacids?
- gaviscon
- peptac
What do NSAIDs disrupt in terms of gastric secretions?
- inhibit COX-1
- Reduced availability of prostaglandins results in histamine secretion from enterochromaffin-like cells
- promoting HCl secretion
What does misoprostol do?
- analogue of prostaglandin E1
- analogue agonist of prostaglandin E1
- Reduces gastric acid secretions
What are proton pump inhibitors
- irreversibly inhibit H+/K+ ATPase pump
- reduces HCl secretion
- examples: lansoprazole, omeprazole etc.
What is an effect of having a low pH in the stomach?
- reduces defences against infection via the GI tract
Examples of histamine H2 receptor antagonists, and what do they do?
- ranitidine, cimetidine
- block H2 receptor, eventually reduces HCl secretion
Explain the effect of a H.pylori infection on the gastric lining
- The H. pylori bacteria weakens the protective mucous coating of the stomach and duodenum, - - allowing acid to get through to the sensitive lining beneath. -Both the acid and the bacteria irritate the lining and cause a ulcer.
How would you treat a H.pylori infection that forms a peptic ulcer?
- Proton pump inhibitors
- antibiotics (clarithromycin and amoxicillin)
What is vomiting triggered by?
- triggered by the vomiting/emetic centre located in the brain stem
What is unusual about the blood brain barrier in the chemoreceptor trigger zone?
- fairly porus
- toxins can get in and activate the neurons within that area
- eventually resulting in the vomiting reflex
What are the main neurotransmitters involved in nausea/vomiting?
- 5-HT
- dopamine
- ACh
Antihistamines act on what receptor?
- H1 receptor antagonists
What are some examples of antihistamines?
- cyclizine
- promethazine
5 examples of anti-emetic drugs?
- anti-histamines
- anti-muscarinics
- 5HT3 receptor antagonists
- dopamine receptor antagonists
- neurokinin-1 receptor antagonists
Side effects of antihistamines?
- sedation
- because they act at H1 receptors in the brain
Antimuscarinics act at what receptor?
- muscarinic acetylcholine receptor antagonist
Side effects of antimuscarinics
- dry mouth
- tachycardia
- constipation
How do 5-HT3 receptor antagonists work as an anti-emetic?
- antagonist in the chemoreceptor trigger zone of the medulla in the hindbrain and in the GI tract
Side effects of 5-HT3 receptors?
- constipation
- diarrhoea
- headache
What receptors do dopamine receptor antagonists act on for an anti-emetic effect?
- D2 receptors in the chemoreceptor trigger zone of the medulla in the hindbrain and in GI tract
Side effects of dopamine receptor antagonists?
- diarrhoea
How do antidiarrhoeal drugs work?
- electrolyte replacements
- some opiates bind to µ-opiate receptors
What drugs can be used in the prevention and treatment of peptic ulcers?
- Proton Pump Inhibitors
- H2 receptor antagonists
What drugs would be used to treat GORD?
- H2 receptor antagonists
- Proton Pump inhibiotrs
- Alignates and Antacids
- Antiemetics
What are the metabolic functions of the liver?
- regulation of carbohydrate, lipid and amino acid metabolism
What hormones are deactivated in the liver?
- insulin
- glucagon
- ADH
- steroid hormones
What hormones are activated in the liver?
- T3
- 25- Hydroxyvitamin D2
What storage function does the liver have?
- fat soluble vitamins
- water soluble vitamins (B12)
- iron, copper
- glycogen
What proteins are synthesised in the liver?
- albumin
- apolipoprotiens
- carrier proteins
What protection effect does the liver have?
- kupffer cells
- production of immune factors
What dexotification function does the liver have?
- endogenous (bilirubin)
- drugs etc.
What happens to bile between meals?
- produced continously
- stored and concentrated in the gallbladder
- sphincter of Oddi closed
What happens to bile during meals?
- chyme in the duodenum, stimulates the smooth muscle of the gallbladder to contract (CCK, vagal impulses)
- sphincter of Oddi opens
What do secretions from hepatocytes contain?
- primary bile acids
- water and electroylets
- IgA
What drug may be suitable for cholelithiasis?
- ursodeoxycholic acod
What are resins used to treat?
- hyperlipidaemia
- cholestatic jaundice
- bile acid diarrhoea
Explain how hepatic encephalopathy occurs?
- severe hepatic failure
- detoxification of ammonia via urea cycle fails
- blood NH3 levels rise exerting a toxic effect
What may be used as indirect treatments of hepatic encehpaholpathy?
- lactulose
- antibiotics
