Which system is primarily affected by tetanus?
**Core Concept**
Tetanus is a bacterial infection caused by Clostridium tetani, which produces a potent neurotoxin that affects the nervous system. The primary mechanism of tetanus involves the blockade of inhibitory neurotransmitters in the central nervous system, leading to excessive muscle contraction and rigidity.
**Why the Correct Answer is Right**
The tetanus toxin, also known as tetanospasmin, binds to ganglionic neurons and inhibits the release of glycine and GABA, two inhibitory neurotransmitters. This inhibition results in the unopposed action of excitatory neurotransmitters, leading to muscle spasms and rigidity. The toxin also affects the autonomic nervous system, leading to symptoms such as hypertension and tachycardia.
**Why Each Wrong Option is Incorrect**
* **Option A:** The skeletal system is not directly affected by tetanus, although muscle spasms can cause damage to bones and joints.
* **Option B:** The cardiovascular system is affected indirectly by tetanus, due to the toxin's effects on the autonomic nervous system, but it is not the primary system affected.
* **Option D:** The respiratory system can be affected by tetanus, particularly in severe cases where muscle spasms can lead to respiratory failure, but it is not the primary system affected.
**Clinical Pearl / High-Yield Fact**
Tetanus toxin is highly resistant to heat and can survive for extended periods in the environment, which is why tetanus is often associated with wounds contaminated with soil or feces.
**Correct Answer:** C. Nervous system.