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Difficulty: MediumHuman Physiology, Health, and Diseases

Which of the following human physiological systems is directly affected by the neurological toxin secreted during an infection by Clostridium tetani, leading to persistent skeletal muscle spasms?

  1. A
    Inhibition of motor neuron signal transmission by destroying acetylcholinesterase at neuromuscular junctions
  2. Blockade of inhibitory neurotransmitter release such as GABA and glycine in the central nervous systemAnswer
  3. C
    Viral destruction of anterior horn cells in the spinal cord leading to flaccid paralysis
  4. D
    Protozoan destruction of red blood cells causing systemic hypoxia and muscular tetany

Answer

Blockade of inhibitory neurotransmitter release such as GABA and glycine in the central nervous system
Tetanus is caused by the bacterium Clostridium tetani. Its exotoxin, tetanospasmin, selectively prevents the presynaptic release of inhibitory neurotransmitters (such as GABA and glycine) across spinal interneurons. Loss of inhibition leads to hyper-reflexia and violent muscle spasms.

Step-by-Step Solution

1
Identify the pathogen and its specific toxin mechanism
Clostridium tetani is an anaerobic bacterium that produces the potent neurotoxin tetanospasmin.
Understanding the pathogen category (bacterial exotoxin) helps distinguish tetanus from viral or protozoan neuromuscular disorders.
2
Analyze the physiological effect of tetanospasmin on neurotransmission
Tetanospasmin retrogradely travels to interneurons in the central nervous system and blocks the release of inhibitory neurotransmitters (glycine and GABA).
Without inhibitory signals, motor neurons fire uncontrollably, resulting in reflex spasms and lockjaw (spastic paralysis).

Key Concept

Tetanus Neurotoxic Pathology and Neuromuscular Physiology
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Topics

Human Physiology, Health, and Diseases

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