What is a primary effect of barbiturates on the central nervous system?

Barbiturates are primarily known for their depressant effects on the central nervous system (CNS). They act by enhancing the activity of gamma-aminobutyric acid (GABA), a neurotransmitter that has inhibitory effects. This results in sedation, hypnosis, and general CNS depression, which can lead to decreased anxiety, muscle relaxation, and even anesthesia at higher doses.

This depressant effect can be beneficial in medical settings for procedures requiring sedation or in managing certain types of seizures. It is critical for healthcare professionals to understand this aspect when considering the use of barbiturates, as it can significantly influence patient care, especially in radiology where sedation may be necessary for imaging procedures.

The other options reflect effects that are not characteristic of barbiturates. Increasing heart rate and stimulating respiration are generally associated with stimulants or certain physiological stress responses, while enhancing alertness contradicts the primary depressant action of barbiturates.