What effect does parasympathetic stimulation have on pacemaker potential?

Parasympathetic stimulation, primarily through the action of the neurotransmitter acetylcholine, exerts an inhibitory effect on the activity of the pacemaker cells located in the sinoatrial (SA) node of the heart. This stimulation leads to a decrease in heart rate by decreasing the slope of the pacemaker potential, which is the gradual depolarization that occurs during the diastolic phase of the cardiac cycle.

When the slope is decreased, it results in a slower rate of depolarization, meaning it takes longer for the pacemaker potential to reach the threshold necessary to trigger an action potential. Consequently, this reduced slope slows down the overall heart rate. The balance between sympathetic and parasympathetic stimulation is crucial for regulating heart rate and ensuring it responds appropriately to the body's needs.