CVS Practice Test

Stimulating M2 receptors in the heart primarily leads to a decreased heart rate and decreased conduction speed. M2 receptors are a subtype of muscarinic acetylcholine receptors that are primarily located in the heart, particularly in the atria and the sinoatrial (SA) node, which is responsible for regulating heart rate. When these receptors are activated, they have a direct inhibitory effect on the pacemaker cells in the SA node, resulting in a reduction in heart rate, also known as negative chronotropic effect.

Additionally, the stimulation of M2 receptors slows down conduction through the atrioventricular (AV) node, leading to decreased conduction speed. This negative dromotropic effect means that the electrical impulses that travel through the heart are slowed, which can be beneficial in certain situations, such as in reducing rapid heart rates or arrhythmias.

The other choices do not correctly reflect the physiological responses associated with M2 receptor activation in the heart. For instance, increased heart rate and decreased vascular tone would imply sympathetic stimulation rather than the parasympathetic effects mediated by M2 receptors. The options involving increased contractility and vasoconstriction are not aligned with the primary roles of M2 receptor activation, which tends to counteract those effects.