Think about something you remember well. Most likely that something produced an emotional response in you. Be it positive or negative, the more intense your emotional response, the stronger your memory of that particular event. It turns out that memories encoded through emotions are the strongest of all our memories.
Cortisol gets released from the adrenal glands (located above the kidneys) in response to strong stimuli, especially if the stimuli causes you some stress, again either positive or negative. Research has shown that cortisol plays a role in memory and learning, although too much of it causes the opposite effect of not thinking or remembering clearly. When the brain perceives strong stress, cortisol partners with adrenaline to deal with fight or flight. A little bit of cortisol is helpful but too much of it can be detrimental.The Human Brain and Stress page at The Franklin Institute Science Museum contains informative explanations of the effects of noise on creating stress within the brain, and the impact of stress on memory and gender. About three-quarters along on the page you will find information about the role of Cortisol.