The nervous system of nematodes is described as consisting of which components?

• A. Nerve cord and ring
• B. Brain and dorsal nerve cord
• C. Nerve net
• D. Ganglia

Answer: (A)

Nematodes have a simple, centralized nervous system organized as a nerve ring around the pharynx and a ventral nerve cord running along the body. The ring acts as a basic processing center, integrating sensory input from around the mouth and pharynx, while the ventral nerve cord carries motor signals to the body-wall muscles to coordinate movement. This arrangement is distinct from a diffuse nerve net (as in cnidarians) and from a brain with a dorsal nerve cord (seen in chordates and other more complex lineages). Therefore, describing the nervous system as a nerve ring plus a nerve cord best reflects the nematode pattern.