Textbook Question
Ergot alkaloids are produced by some strains of the genus _____ .
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21. Principles of Disease
Introduction to Pathogenic Toxins
2:38 minutesProblem 10
Textbook Question
Explain the action of the toxin of Clostridium tetani.
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Identify that the toxin produced by Clostridium tetani is called tetanospasmin, which is a neurotoxin responsible for the symptoms of tetanus.
Understand that tetanospasmin acts by targeting the central nervous system, specifically the inhibitory neurons that regulate muscle contraction.
Explain that the toxin enters the peripheral nervous system at the site of infection and travels retrograde along motor neurons to the spinal cord.
Describe how tetanospasmin blocks the release of inhibitory neurotransmitters such as gamma-aminobutyric acid (GABA) and glycine by cleaving synaptobrevin, a protein essential for neurotransmitter vesicle fusion.
Conclude that this inhibition leads to unregulated muscle contraction and spastic paralysis, which are characteristic of tetanus.
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2mKey Concepts
Here are the essential concepts you must grasp in order to answer the question correctly.
Clostridium tetani and Its Characteristics
Clostridium tetani is a Gram-positive, anaerobic, spore-forming bacterium responsible for tetanus. It thrives in low-oxygen environments like deep wounds, producing a potent neurotoxin. Understanding its biology helps explain how infection and toxin production occur.
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Tetanospasmin (Tetanus Toxin) Structure and Mechanism
Tetanospasmin is the neurotoxin produced by C. tetani, composed of heavy and light chains. It binds to peripheral nerves, travels retrograde to the central nervous system, and blocks inhibitory neurotransmitter release, causing muscle rigidity and spasms.
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Pathophysiology of Tetanus Toxin Action
The toxin inhibits release of inhibitory neurotransmitters like GABA and glycine in the spinal cord, leading to unregulated motor neuron firing. This results in sustained muscle contractions and characteristic symptoms such as lockjaw and muscle spasms.
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