Lecture 11 things to work on

Question 1

What causes the release of histamine?

Answer 1

The vagal nerve stimulates the enteric nerves which causes the release histamine from the ECL cells.

Question 2

What receptor does histamine bind to on the parietal cell?

Answer 2

it binds to the H2 receptor

Question 3

What happens when histamine binds to its H2 receptor on the parietal cell?

Answer 3

The H2 receptor is a GPCR when means that when histamine binds, GDP is converted to GTP. The subunit dissociates and activates adenylate cyclase. This converts ATP to cAMP which activates PKA and this phosphorylates the N+/K+ pump and causes it to move to the membrane. This causes H+ to leave the cell, and Cl- leaves apically through CFTR to cause an increase in Hal

Question 4

What happens when ACh innervates the parietal cells?

Answer 4

• Vagal nerve stimulates the enteric nerve
• ACh is released from the vagal nerve
• ACh binds to the M3 receptor
• PLC breaks down PIP2 into IP3 and DAG
• DAG activates PKC
• IP3 binds to its receptor in the ER, Ca2+ is pumped out of the ER
• H+/K+ pump is exocytosed to the apical membrane

Question 5

What is the major stimulus for digestive enzyme secretion from the pancreatic acini?

Answer 5

CCK

Question 6

What is the major stimulus for the duct cells to secrete bicarbonate rich fluid?

Answer 6

secretin

Question 7

How does CCK stimulate the exocytosis of digestive enzymes?

Answer 7

CCK binds to its CCK1 receptor (GPCR) which activates PLC. PLC breaks down PIP2 into IP3 and DAG. DAG activated PKC. IP3 causes the release of Ca2+ from the endoplasmic reticulum. There is then exocytosis of zymogen granules

Question 8

How does secretin stimulate the secretion of bicarbonate rich fluid?