Question

The neurons may get irreversibly damaged if exposed to significant hypoxia for

• A. 8 minutes
• B. 2 minutes
• C. 30 seconds
• D. 15 seconds

Hint:

Standard teaching puts irreversible neuron damage at about 4 to 6 minutes of complete anoxia; this paper's key is self flagged as uncertain.

Answer 1

The Correct Option is A

This question is about the time limit after which oxygen starved neurons cannot recover, a number that different textbooks state slightly differently.

1. 8 minutes: This is the option marked in the original answer key. It falls in the same broad range, several minutes, as commonly quoted teaching values, though it runs a bit longer than the tightest textbook figures.
2. 2 minutes: Some sources treat this as the point where reversible stress starts to build, but most standard teaching still allows a little more time than this before damage becomes permanent.
3. 30 seconds: Far too short. This length of oxygen loss usually causes only brief, reversible symptoms such as light headedness, not lasting neuron death.
4. 15 seconds: Also far too short for permanent injury, this is closer to the time it takes to feel dizzy from a sudden drop in brain blood flow, not to cause fixed damage.

The commonly quoted textbook range for irreversible cortical neuron injury is about 4 to 6 minutes of complete anoxia at normal body temperature. None of the four options match this exactly, and the source paper itself marks its own chosen answer with a question mark, noting the 3 to 5 minute range as the more standard figure.

Let's summarize:

• Neurons have almost no energy reserve and depend on constant oxygen delivery, so anoxia damages them faster than most other tissues.
• Most texts place the irreversible injury point at about 4 to 6 minutes, though this exact paper's key and annotation disagree slightly on the number.

Following the original key, the marked answer here is 8 minutes, with the caveat that standard teaching favors a shorter window of about 4 to 6 minutes.