Final answer:
The headache your friend is experiencing after cutting down on their caffeine intake is due to Rebound Adenosine inhibition. When your friend consumed a large amount of caffeine regularly, the adenosine receptors in their brain became desensitized, leading to a dependence on caffeine for alertness. The correct option is a.
Step-by-step explanation:
The headache your friend is experiencing after cutting down on their caffeine intake is due to Rebound Adenosine inhibition.
Caffeine is thought to block the activity of adenosine, a neurotransmitter that helps regulate sleep and wakefulness.
When your friend consumed a large amount of caffeine regularly, the adenosine receptors in their brain became desensitized, leading to a dependence on caffeine for alertness.
When your friend abruptly reduced their caffeine intake, the adenosine receptors in their brain became overactive, causing a rebound effect.
This leads to vasoconstriction and an increase in blood pressure, which can result in a headache. The correct option is a.