Tasks 4-5

4. Effects of Acetylcholine

1. measure the heart rate before and at 20s after the application of acetylcholine.
2. observe any changes in the amplitude (force) of both atrial and ventricular contraction.
3. explain the observed actions of acetylcholine and suggest how acetylcholine might affect pacemaker activity. At what type of receptor on cardiac muscle cells does acetylcholine act. Briefly explain this action.

5. Effects of Acetylcholine in the presence of Physostigmine (eserine)

1. measure the heart rate before and at 20s after the application of acetylcholine against a background of physostigmine. Record control heart rate, heart rate after physostigmine alone and heart rate after physostigmine and acetylcholine.
2. explain the action of physostigmine.