The Question is from neet-zoology neural-control-and-coordination , and it was created by the author K SUNKANNA

Question

A neuron poisoned with tetrodotoxin (TTX) is stimulated. Which of the following would be observed?

K SUNKANNA · Accepted Answer

## CORE INFORMATION
✓ **Answer**: C
## CONCEPT FRAMEWORK
 **Primary Concept**: Action potential generation and the role of ion channels
 **Related Topics**: Neurotoxins, membrane potential, sodium channels, potassium channels
 **Prerequisites**: Understanding of the action potential mechanism, the role of voltage-gated sodium and potassium channels.
## SOLUTION PATHWAY
**Given Information**:
A neuron is poisoned with tetrodotoxin (TTX).
The neuron is stimulated.
**Method & Steps**:
1. Understanding the role of TTX:
  Reasoning: Tetrodotoxin (TTX) is a potent neurotoxin that selectively blocks voltage-gated sodium ($Na^+$) channels.  These channels are crucial for the initiation and propagation of action potentials.
  Formula/Rule:  None directly applicable, but understanding the role of $Na^+$ channels in action potential generation is crucial.
2. Analyzing the effect of blocked $Na^+$ channels:
  Working: When $Na^+$ channels are blocked, the influx of $Na^+$ ions into the neuron during depolarization is prevented.  Depolarization is the initial phase of an action potential, where the membrane potential becomes less negative. Without this influx, the neuron cannot reach the threshold potential required to trigger an action potential.
  Key Point: The rising phase of the action potential is directly dependent on the opening of voltage-gated $Na^+$ channels.
3. Determining the observed outcome:
  Result: Since the $Na^+$ channels are blocked, no action potential will be generated.
  Verification: This aligns with the known mechanism of TTX action.
 ## OPTION ANALYSIS
A :x: Normal action potential generation is impossible because TTX blocks $Na^+$ channels.
B :x: Delayed action potential generation is not observed; the action potential is completely blocked.
C ✓: No action potential generated due to blocked $Na^+$ channels is the correct observation. TTX directly inhibits the opening of voltage-gated sodium channels, preventing depolarization and action potential generation.
D :x: Hyperexcitability and spontaneous action potentials are not observed; instead, the neuron is functionally silenced due to the blocked $Na^+$ channels.
 ## LEARNING AIDS
 **Common Mistakes**:
  1.Confusing the effects of TTX with other neurotoxins:  Other neurotoxins may affect different ion channels or have different mechanisms of action.
  2.Assuming that the neuron will still partially function: TTX's effect on $Na^+$ channels is quite potent, leading to a complete block of action potential generation.
 **Quick Tips**:
  1.Remember the key role of $Na^+$ channels in the rising phase of the action potential.
  2.Associate TTX with the complete blockage of action potential generation.

K SUNKANNA · Answer

Normal action potential generation

K SUNKANNA · Answer

Delayed action potential generation

K SUNKANNA · Answer

The correct Option is "No action potential generated due to blocked $Na^+$ channels"

K SUNKANNA · Answer

Hyperexcitability and spontaneous action potentials

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