CVS Practice Test

True or False: M2 receptors have a negative effect on chronotropy, dromotropy, and inotropy in the heart.

1. True

2. False

3. Only on dromotropy

4. Only on inotropy

The correct answer is: True

M2 receptors are a subtype of muscarinic acetylcholine receptors that play a crucial role in modulating the activity of the heart. When activated, M2 receptors exert a negative effect on chronotropy (the rate of heartbeats), dromotropy (the conduction speed through the heart's conduction system), and inotropy (the force of heart muscle contraction). This negative effect occurs primarily due to the inhibitory influence of the parasympathetic nervous system, mediated by acetylcholine binding to these receptors. In particular, activation of M2 receptors leads to a decrease in heart rate by slowing down the firing of the sinoatrial (SA) node, which is responsible for initiating heartbeats. Furthermore, it also decreases conduction velocity through the atrioventricular (AV) node, affecting dromotropy, and reduces the overall contractility of the cardiac muscle, impacting inotropy. Thus, the statement is true; M2 receptors do indeed have a negative effect on chronotropy, dromotropy, and inotropy in the heart. This understanding is important for grasping the pharmacological actions of drugs that influence the autonomic nervous system and their clinical implications in cardiovascular health.