Calcium uptake by mitochondria makes heart beat harder in fight-or-flight response

In a life-threatening situation, the heart beats faster and harder, invigorated by the fight-or-flight response, which instantaneously prepares a person to react or run. Now, a new study shows that the uptick in heart muscle contractility that occurs under acute stress is driven by a flood of calcium into mitochondria -- the cells' energy-producing powerhouses.