L3 - How Drugs Work - Part 3

Question 1

what are the uses of calcium signalling

Answer 1

• first signal following fertilisation
• muscle contraction
• secretion
• metabolism
• neuronal excitability
• cell proliferation

Question 2

What is Ca²⁺

how does it work

what are its actions

Answer 2

• second messenger
• neither produced nor destroyed
  
  • moved between compartments
• effect are conc-dependant
• actions
  
  • activation of specific protein kinases, ion channels
  • regulation of activity of many enzymes

Question 3

How is Ca²⁺ transported

Answer 3

• calcium release activated channels (CRAC)
  
  • = store operated Ca²⁺ channels
• Ca²⁺ transporters (PMCA)
• Voltage operated channels (VOC)
• ligand-gated channels

Question 4

What are the Ca²⁺ channel blockers used for

give examples

Answer 4

• nifedipine, verapamil
• used to modulate muscle contraction

Question 5

intracellular Ca²⁺ release channels

Answer 5

• 2 receptors
  
  • Inositol trispjposphate receptor (IP₃R)
  • ryanodine receptor
• trans-membrane proteins of intracellular Ca²⁺ stores (organelles, e.g. nucleus, ER/SR)
• release Ca²⁺ in cytosol
  
  • in response to an increase in intracellular IP₃ or Ca²⁺
• functional effect
  
  • e.g. contraction, proliferation

Question 6

how does excitation-contraction coupling in smooth muscle work

Answer 6

Question 7

What is the function of parietal cells

Answer 7

produce HCl

Question 8

what are the chemicals that influence the activity of the proton pump

Answer 8

• histamine
• acetylcholine
• gastrin

Question 9

How does histamine influence the rate of the proton pump reaction

Answer 9

• binds to the Histamine H₂ receptor
• cAMP released as secondart messenger

Question 10

How does acetylcholine and gastrin influence the rate of the proton pump reaction

Answer 10

• bind to receptor
• release Ca²⁺ as secondary messenger

Question 11

How is acid secretion controlled

Answer 11

ACh is acetylcholine

prostglandin inhibit proton pump

Question 12

target for drugs in GI tract

Answer 12

• histamine receptors
  
  • e.g. ranitidine
  • target: parietal cells - gastric acid secretion
• opioid receptors
  
  • e.g. loperamide
  • target: Myenteric plexus – decreased peristalsis, increases tone of anal sphincter (Ca²⁺ channel blocker)