How do CNS stimulants primarily affect the central nervous system?

CNS stimulants primarily speed up the operation of the brain and spinal cord by increasing the activity of neurotransmitters responsible for signaling in the central nervous system. This heightened level of stimulation results in enhanced alertness, increased concentration, and improved energy levels.

Stimulants such as amphetamines and cocaine can elevate mood and decrease fatigue, which is reflected in the performance of various mental tasks. They work by promoting the release of neurotransmitters like dopamine and norepinephrine, which are crucial for processes that govern attention, arousal, and emotional responses. As a result, users often experience heightened cognitive function, faster reaction times, and increased physical activity.

In contrast, options that suggest slowing down brain function or inducing calmness are indicative of depressants, which have the opposite effect on the central nervous system. Enhancing memory retention may occur as a secondary effect, but it is not the primary mechanism by which stimulants operate. Thus, the correct answer emphasizes the stimulatory effects on cognitive and physical activity rather than any calming or memory-specific functions.