Final answer:
Depressants are the category of substances that depress nerve function, affecting various bodily functions including judgment and muscle control, and are exemplified by drugs such as benzodiazepines and alcohol.
Step-by-step explanation:
The category of substances that depress nerve cells, affecting judgment, voluntary muscle control, and eventually respiration and heart action is c) Depressants. These substances lower neurotransmission levels in the brain which leads to a reduced level of arousal or stimulation. Common examples of depressants include alcohol, barbiturates, and benzodiazepines such as Xanax. Depressants can also serve as agonists of the gamma-Aminobutyric acid (GABA) neurotransmitter system, which has a quieting effect on the brain.
When taken, depressants can result in various effects such as ataxia, anxiolysis, pain relief, sedation, and cognitive impairment. In some instances, they can produce effects like euphoria, muscle relaxation, and lowered heart rate or blood pressure. It's worth mentioning that the use of depressants, like any other drugs, can lead to substance use disorder if misused or abused.