The Purpose of Stress

...is to form memories?

According to the latest volume of Nature:

Neuroscience: Stressing memory

J. Neurosci. 30, 5037–5046 (2010)

The emotional arousal associated with a class of stress hormones may be required to form long-term memories, say Benno Roozendaal at the University of Groningen in the Netherlands, Marcelo Wood at the University of California, Irvine, and their colleagues.

The authors gave glucocorticoid hormones to rats and mice and tested how well the animals remembered objects and their locations. They found that the hormones improved memory by boosting acetylation, the addition of acetyl groups to nuclear targets.

This modification appears to facilitate some of the gene transcription required to consolidate memories. But promoting acetylation in the absence of the hormone didn't improve memory. The hormone had to first activate receptors on the cell membrane in order to trigger a cascade of events involved in laying down memories.
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SO STRESS YOURSELF OUT IF YOU WANT TO REMEMBER MORE. Well seeing how detrimental everyone is saying these stress hormones are its probably... expected that they have some other role other than making your lifespan shorter. :V