Tetanus is a disease caused by a neurotoxin produced by bacteria that interferes with the nerves that control muscle movement. Which body system is primarily affected?

• A. Nervous system
• B. Digestive system
• C. Circulatory system
• D. Endocrine system

Answer: (A)

Tetanus toxin disrupts neural control of muscles, so the nervous system is the primary target. The toxin blocks the release of inhibitory neurotransmitters like GABA and glycine in motor circuits of the spinal cord and brainstem. Without those brakes, motor neurons fire too much, producing the characteristic rigid, spastic contractions of skeletal muscles. This direct effect on nerve signaling is why the nervous system is the correct focus. The digestive, circulatory, and endocrine systems aren’t the primary sites of the toxin’s action, even though illness can have widespread secondary effects.