A patient exhibits a sudden inability to move their left arm and experiences slurred speech. Which part of the nervous system is most likely affected?

A. Central nervous system: Sudden focal motor deficits (e.g., inability to move one limb) and speech disturbance typically indicate a lesion in the brain (cerebral cortex, internal capsule, brainstem) or spinal cord - structures of the central nervous system (CNS). Common causes include stroke (ischemic or hemorrhagic), intracerebral hemorrhage, or a space-occupying lesion affecting motor or language areas.

B. Enteric nervous system: The enteric nervous system governs gastrointestinal motility, secretion, and blood flow within the gut. It does not control voluntary limb movement or speech, so it is not responsible for these focal neurological signs.

C. Peripheral nervous system: The peripheral nervous system (PNS) includes peripheral nerves and roots. PNS lesions produce patterns such as peripheral neuropathy, mononeuropathy, or radiculopathy (sensory loss, distal weakness, reflex changes) but rarely cause acute combined limb paralysis plus dysarthria from a single focal lesion affecting both motor cortex and language pathways - that pattern points to CNS pathology.

D. Autonomic nervous system: The autonomic nervous system controls involuntary functions (heart rate, blood pressure, digestion, pupil size). Autonomic dysfunction would not cause isolated sudden motor loss of an arm or slurred speech.