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Ch. 11 Introduction to the Nervous System and Nervous Tissue
All textbooksErin C. Amerman 2nd EditionCh. 11 Introduction to the Nervous System and Nervous TissueProblem 11.3a
Chapter 11, Problem 11.3a

Albert accidentally ingests the poison tetrodotoxin from the pufferfish, which you know blocks voltage-gated Na+ channels. Predict the symptoms Albert will experience from this poisoning.

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Understand that tetrodotoxin blocks voltage-gated Na+ channels, which are crucial for the initiation and propagation of action potentials in neurons.
Recognize that blocking these channels will prevent the influx of Na+ ions, which is necessary for depolarization of the neuron membrane.
Consider that without depolarization, action potentials cannot be generated or propagated along neurons, leading to a failure in nerve signal transmission.
Predict that the symptoms will likely include muscle weakness or paralysis, as motor neurons cannot transmit signals to muscles effectively.
Acknowledge that sensory neurons will also be affected, potentially leading to numbness or loss of sensation, and severe cases may involve respiratory failure due to paralysis of the diaphragm.

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Key Concepts

Here are the essential concepts you must grasp in order to answer the question correctly.

Tetrodotoxin

Tetrodotoxin is a potent neurotoxin found in certain species of pufferfish. It works primarily by blocking voltage-gated sodium channels in nerve cells, preventing the influx of sodium ions necessary for action potentials. This disruption in neuronal signaling can lead to paralysis and respiratory failure, making it a critical substance to understand in toxicology.

Voltage-Gated Sodium Channels

Voltage-gated sodium channels are integral membrane proteins that open in response to changes in membrane potential, allowing sodium ions to flow into the cell. This influx is essential for the depolarization phase of action potentials in neurons and muscle cells. When these channels are blocked, as with tetrodotoxin, it results in a failure to propagate nerve impulses, leading to muscle weakness and loss of sensation.
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Symptoms of Poisoning

The symptoms of tetrodotoxin poisoning can include numbness, tingling, muscle weakness, and paralysis, particularly in the limbs and respiratory muscles. As the toxin affects the nervous system, it can also lead to cardiovascular issues and potentially fatal respiratory failure. Understanding these symptoms is crucial for diagnosing and managing cases of poisoning effectively.
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Related Practice
Textbook Question

Mark the following statements as true or false. If a statement if false, correct it to make a true statement.


c. An inhibitory postsynaptic potential causes the membrane potential of the postsynaptic neuron to approach threshold.

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Textbook Question

​​What would happen if the drug blocked K+ channels instead?

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Textbook Question

During a surgical procedure, an anesthesiologist administers to the patient an inhaled anesthetic agent that opens Cl− channels in the postsynaptic membranes of neurons in the brain. Explain why this would put the patient 'to sleep' for the duration of the surgical procedure.

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Textbook Question

Explain how an action potential is propagated down an axon in continuous conduction. Why is saltatory conduction faster than continuous conduction?

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Textbook Question

Albert, the patient in question 3, takes the drug lithium, which reduces the permeability of the neuronal axolemma to Na+ (that is, it allows fewer Na+ to enter the axon). Predict the effect this would normally have on his neuronal action potentials. Do you think this drug would be beneficial or harmful, considering his condition?

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Textbook Question

P​​redict the effect that tetrodotoxin would have on Albert's muscle fiber action potentials (see question 3). Would it affect end-plate potentials at the motor end plate? Why or why not? (Connects to Chapter 10)

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