Final answer:
The tetanus toxin produced by Clostridium tetani affects voluntary muscles by preventing the release of neurotransmitters that normally relax muscles, leading to permanent muscle contraction and symptoms like lockjaw. The correct answer is b. Voluntary muscles.
Step-by-step explanation:
The toxin produced by tetanus, known as tetanus toxin or TeNT, primarily affects voluntary muscles. Tetanus toxin is produced by Clostridium tetani, a gram-positive bacterium. This neurotoxin consists of a light A subunit and heavy chain B subunit and binds to inhibitory interneurons at the neuromuscular junction. These interneurons are normally responsible for the release of inhibitory neurotransmitters glycine and gamma-aminobutyric acid (GABA), which are essential for inhibiting acetylcholine release and thus relax muscles. However, tetanus toxin inhibits the release of these neurotransmitters, leading to permanent muscle contractions. This results in symptoms such as lockjaw and violent muscle spasms and can lead to respiratory failure and death if the spasms affect the respiratory muscles. Tetanus can result in either localized or generalized forms. In generalized tetanus, the toxin can spread and affect voluntary muscles throughout the body, not just near the wound site. Therefore, the correct answer is b. Voluntary muscles.