Tetanus Toxin

Summary

Tetanus is a painful disease caused by the bacterium *Clostridium tetani*. It leads to continuous muscle spasms due to a disruption in the normal balance of excitatory and inhibitory signals in the nervous system. The toxin produced by the bacteria interferes with the ability of inhibitory neurons to release neurotransmitters, causing unopposed excitatory signals that result in uncontrollable muscle contractions. The hallmark symptoms include a stiff back, flexed arms, and extended legs. If untreated, it can lead to death through asphyxiation due to respiratory failure caused by the spasms.

Takeaways

• 😀 Tetanus is a painful disease caused by continuous and involuntary muscle contractions.
• 😀 Normally, muscle contractions are regulated by both excitatory and inhibitory neurons.
• 😀 In tetanus, inhibitory neurons fail to release their neurotransmitters, leading to unopposed excitatory signals.
• 😀 Tetanus is caused by the bacterium *Clostridium tetani*, which is found in soil and enters the body through wounds.
• 😀 The bacterium releases a potent exotoxin called tetanospasmin, which affects motor neurons.
• 😀 Tetanospasmin travels along motor neurons and enters the spinal cord, where it binds to inhibitory neurons.
• 😀 The toxin disrupts normal neurotransmitter release by cleaving specific proteins, preventing muscle relaxation.
• 😀 Tetanus causes muscle spasms, leading to symptoms like arching of the back and flexion of the arms with extension of the legs.
• 😀 Without treatment, severe tetanus can lead to death, often due to asphyxiation caused by muscle spasms.
• 😀 Tetanus is treated by managing symptoms and administering antitoxin to neutralize the toxin.

Q & A

What is tetanus, and how does it affect the body?

Tetanus is a disease caused by a bacterium called *Clostridium tetani*. It leads to continuous, involuntary muscle contractions and spasms due to the failure of inhibitory neurons to release their neurotransmitters, resulting in unopposed excitatory signals to the muscles.

How do muscles normally contract in the body?

Muscles contract based on signals from both excitatory and inhibitory neurons. Excitatory neurons stimulate the motor neurons to send signals to muscle fibers, while inhibitory neurons balance the excitatory signals to modulate the strength of muscle contractions.

What happens to the neural signaling in the body during tetanus?

During tetanus, the inhibitory neurons fail to release their neurotransmitters, allowing the excitatory neurons to act unopposed. This leads to continuous muscle contractions and spasms characteristic of the disease.

What bacterium causes tetanus, and how does it enter the body?

*Clostridium tetani* is the bacterium that causes tetanus. The spores of this bacterium are commonly found in soil and can enter the body through wounds, where anaerobic conditions support their growth.

What role does the tetanus toxin play in the disease?

The tetanus toxin, called tetanospasmin, affects motor neurons by preventing the release of neurotransmitters from inhibitory neurons. This disruption of normal neural function leads to unopposed excitatory signaling, causing continuous muscle spasms.

How does the tetanus toxin travel to the spinal cord?

The tetanus toxin enters motor neurons and is transported in a retrograde manner up the long axon to the spinal cord, where it binds to inhibitory neurons and interferes with their function.

What is the molecular mechanism that prevents neurotransmitter release in tetanus?

The tetanus toxin acts as a protease that cleaves a protein called BAM (VAMP), which is necessary for synaptic vesicles to fuse with the plasma membrane and release neurotransmitters. Without this fusion, inhibitory neurotransmitters cannot be released, leading to excessive excitatory signaling.

How does the lack of inhibitory signals cause the symptoms of tetanus?

Without inhibitory signals, the excitatory neurons send uncontrolled signals to muscles, leading to persistent muscle contractions and spasms. This results in symptoms such as a rigid, arched back and flexed arms and extended legs.

What can happen if tetanus is left untreated?

If left untreated, tetanus can lead to severe muscle spasms, affecting the diaphragm and potentially causing asphyxiation, which can lead to death.

How can tetanus be prevented?

Tetanus can be prevented through vaccination with the tetanus toxoid vaccine, which provides immunity against the tetanus toxin. Proper wound care and hygiene are also important in preventing infection.