B4 The upper GI tract 3 Flashcards
What is released by the vagus nerve?
acetylcholine
What does ACh act on?
Muscarinic M3 receptor
What type of receptor is an M3 receptor
G-protein-coupled receptor (GPCR)
What is histamine?
an endogenous mediator, hormone
What is histamine responsible for?
Skin rashes
gastric acid secretion
What are the 3 histamine receptors?
GPCRs
histamine H1 recpetors
histamine H2 receptors
What do H1 and H2 receptors do and what can be used to treat them?
H1- allergy, antihistamines-lotatadine
H2- gastric acid secretion, antagonist used to treat dyspepsia- ranitidine
What is gastrin?
a peptide hormone
Where is gastrin released for and what does it mediate?
released from antral cells and mediate gastric phase
What is gastrin an agonist for?
CCK2
Is gastrin calcium dependent for activation of proton pump?
yes
What inhibits proton pump action
prostaglandins binding to PG R
What are Prostanoids?
family of endogenous mediators derived from arachidonic acid
How is arachidonic composed?
20 carbon atom unsaturated fatty acid with 4 C=C double bonds
Where is Arachidonic acid located and released by?
located in cell membranes and released by phospholipase A2
What are the two pathways of Arachidonic acid?
Cyclooxgenase (Cox) - release prostanoids
Lipoxygenase- release leukotrienes
What are the family of metabolites prostanoids and prostaglandins belong to? Give 3 examples
AA metabolites
PGI2, PGE2, TXA2
What are the functions of PGI2, PGE2 and TXA2?
PGI2- inhibit acid secretion
PGE2- inhibits platelet aggregation (vasodilation)
TXA2- stimulates platelet aggregation (vasoconstriction)
Give examples of some symptoms prostanoids and prostaglandins do
Pain inflammation raise temp asthma uterine contraction miscarriage
What do PGE2 and PGI2 inhibit and therefore cause?
inhibit increase in cAMP leads to suppression of proton pump activity can cause cytoprotection by releasing mucous and bicarbonate
What are NSAIDs and what do they do?
Non- steroidal anti-inflammatory drugs, which inhibit cyclooxygenase
What are the benefits and disadvantages of NSAIDs?
\+ves - pain relief - anti-inflammatory - anti- pyretic - anti platelet -ves more acid secretion, reduced mucous and bicarbonate
What activates the proton pump?
phosphorylation and calcium
What is meant by dynamic?
produced in cell and cycles to membrane
