## Exposure to stressful conditions that do not kill the cell can help it survive

A phenomenon known as adaptive response is closely related to stress and the response to it. It can be described as cellular "immunity", where a stress that was not lethal to the cell, nor did it cause serious damage, helped prepare the cell for the action of a more severe stressor. This more severe stressor could kill the cell by its action, if cell was not already prepared thanks to the first impulse. The explanation of this phenomenon is that the first stress impulse activates several repair and defence mechanisms. Subsequently, with the second impulse, the cell no longer had to wait for the necessary proteins to be synthesized and could defend itself immediately.

The adaptive response works under different forms of stress. It was discovered during the action of ionising radiation, when scientists found that after the cells were exposed to ionising radiation, DNA damage was lower in the case that the cells were previously affected by lower doses of radiation. The adaptive response not only manifests when both impulses are the same, but it can also be triggered by another impulse, which must activate appropriate defense mechanisms in the cell. The cell will then use them during the second impulse. However, the condition is that the first impulse must not be too strong, otherwise it could weaken the cell, nor too weak so it is unable to activate all the necessary mechanisms.