Which system can be affected by potentially toxic substances?

The central nervous system (CNS) can be significantly affected by potentially toxic substances, which is why it is the correct choice. Toxic substances, such as heavy metals, certain drugs, or environmental toxins, can disrupt the normal functioning of the brain and spinal cord. This disruption may manifest as neurological symptoms, cognitive impairments, or, in severe cases, life-threatening conditions. The CNS is particularly vulnerable because it is responsible for processing and transmitting information throughout the body, and toxins can interfere with neurotransmitter activity and neuronal health.

In comparison, while the digestive system, respiratory system, and other bodily systems can also be impacted by toxic substances, the CNS is unique in its critical role in regulating and coordinating bodily functions through complex networks. Effects on the CNS can be profound and potentially irreversible, making it a primary area of concern when discussing toxic exposure.