1. Although nerve agents are banned in warfare, military personnel may carry atropine to combat nerve gases that block acetylcholinesterase (the enzyme that normally breaks down acetylcholine). a) How would these nerve agents affect firing of the SA node, heart rate, and cardiac output? b) Atropine is carried by many military personnel as an antidote for a potential nerve gas attack. Atropine binds and blocks the acetylcholine receptor. How would atropine affect the frequency of SA node firing, heart rate, and cardiac output? 2. Beta-blockers are receptor antagonists (block the beta receptor) used to treat hypertension. How would this drug affect SA node firing, heart rate, and cardiac output?