Definition of laggard in US English - a person who makes slow progress and falls behind others Definition of laggard in US English - a person who makes slow progress and falls behind others dictionary
Unconsciousness occurs within about 30 seconds, so it's not as if you would have very much time to contemplate what is happening. Once the brain goes unconscious, tissue begins to die after about 5 minutes of oxygen starvation. After this point, there may only be small islands of activity remaining in various brain structures. After ten to fifteen minutes, complete brain death will usually occur. One exception to this is if the brain (and body) are in a state of hypothermia. Extreme cold can induce a process called neuroprotection; metabolism is greatly reduced, and the brain can survive for much longer than it would at room temperature.
By placing a radioactivity counter over the head, one can measure the amount of blood flow into the brain. (See How Nuclear Medicine Works .) The cerebral blood flow study takes 20 to 30 minutes to perform. If there is no blood flow to the brain as demonstrated by this study, the brain is dead.A negative cerebral flow study is indisputable evidence of a dead brain. Normal cerebral blood flow study showing cranial space filled with blood. Cerebral blood flow study showing no blood entering the brain.Another confirmatory test is chemical: The patient can be given 1 mg of atropine IV.In the patient with an intact brain, atropine will dramatically increase the patient's heart rate. In a brain-dead patient, atropine will not influence heart rate.y placing a radioactivity counter over the head, one can measure the amount of blood flow into the brain. (See How Nuclear Medicine Works .) The cerebral blood flow study takes 20 to 30 minutes to perform. If there is no blood flow to the brain as demonstrated by this study, the brain is dead.