Multiple choice

A man will be unconscious if the blood supply to the brain is stopped for more than

  1. 2 seconds

  2. 5 seconds

  3. 10 seconds

  4. 30 seconds
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

The brain is highly sensitive to oxygen deprivation due to its high metabolic rate and minimal energy reserves. When blood supply to the brain is interrupted, unconsciousness occurs rapidly, typically within 5 to 10 seconds. This quick onset of unconsciousness is why fainting (syncope) happens so suddenly during cardiovascular events. Permanent brain damage begins after approximately 4-6 minutes of ischemia.

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