We must pause with awe when it comes to the human brain. We must wonder to contemplate the marvels and mysteries of the three pounds of pinkish-gray tissue contained within our heads. The brain contains upward of 12 billion nerve cells, each of which may potentially be linked to countless others. Possible ""telephone connections"" in switchboards of the brain are so numerous as to be incomprehensible. A credible estimate sets the figure at 10 followed by 23 zeros. Unconsciousness, that last several minutes or more following a head injury, requires close care. Some brain injuries can cause lasting damage to the brain tissue and leave residuals of severe headaches, dizziness, and even paralysis or convulsions. Very severe brain injury with hemorrhage and swelling of the brain substance (compression) can lead to death! The Brain Is Our Spark of Life.