医学英语阅读：为何辛苦劳累却仍难以入眠

 Lack of sleep complicates matters even more. Experts say adults need at least 7 to 8 hours of sleep a night to function properly. When you get less sleep than that on consecutive nights， you begin to accrue "sleep debt." As sleep debt increases （and functionality decreases）， your body experiences a stress response and begins to release adrenaline（= adrenalin肾上腺素）。 Now a vicious cycle has been created： You experience the feeling of being more and more tired， but your body is increasingly stimulated. "Power sleeping" for more hours on weekends is only a temporary solution. "There is no substitute for getting a good night's sleep on a regular basis，" says Hunt.