Pharmacology

Question 1

Describe the effects of acetylcholine on heart rate.

Answer 1

1. activates M2 muscarinic cholinoceptors largely in nodal cells
2. Coupling through G Protein:
   -decreases activity of adenylate cyclase & reduces cAMP
   -opens potassium channels (GIRK) to cause hyperpolarisation of SAN
3. Negative chronotropic effect
   ~decreased slope of pacemaker