Brain's not clear. What's going on?

The brain is not awake, considering that there are generally two reasons. One is excessive mental stress, excessive tension, in order to enable brain cells to work and learn normally, the body has a self-regulatory system, including the awakening system and the sleep system. Under normal circumstances, in the waking state, brain cells are active and excited, which can meet the life, work and study of the body. In the sleep state, cells rest. When excessive tension, mental stress, brain cell activity is too strong, beyond its maximum tolerance, leading to regulatory system dysfunction, will produce the above symptoms. Another reason to consider the lack of blood supply to the brain, brain tissue has blood vessels, carrying oxygen and nutrition supply, if there are cervical spondylosis, arteriosclerosis, hyperlipidemia, hyperglycemia and other performance exists, affecting blood viscosity and blood flow speed, leading to brain cells oxygen supply, blood supply deficiency, will also show this situation.