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Imagine you're getting ready to race. The stress you feel makes your brain signal the adrenal glands to produce epinephrine or "adrenaline". Adrenaline increases your heart rate. As a result, more oxygen gets to your muscles. That makes your body ready to react. In a longer-term response to stress, the glands secrete cortisol. Cortisol promotes the release of energy, making you ready to race.
Review Date 9/7/2021
Updated by: David C. Dugdale, III, MD, Professor of Medicine, Division of General Medicine, Department of Medicine, University of Washington School of Medicine. Also reviewed by David Zieve, MD, MHA, Medical Director, Brenda Conaway, Editorial Director, and the A.D.A.M. Editorial team.