Biology 202
1998 Second Web Reports
On Serendip

There has been a long held rule of thumb that when the heart beat and breathing have stopped, a person was considered dead. One doctor wrote of having to pronounce death on a man when he was still an intern. He relied on a EKG, and electrocardiogram, something that measures the heart rate, to give him his final conclusion of death. To use only that criteria is becoming a grayer and grayer area as medical technology progresses and other issues begin to take the fore. We are now capable of sustaining bodies for extended periods of time and also are now able to transplant organs from one person to another. For obvious reasons you cannot transplant certain organs from human beings without the donor first being dead, and then you have a very limited time within which you must "harvest" the organs. Just because part of the nervous system is functioning does not necessarily mean the rest of the nervous system is. Many people from different walks of life feel that as soon as "higher" functions cease and someone is brain dead, then their organs are fair game if they had previously decided to donate them. (2) That sentiment, while understandable, begs another question, how do you tell when these functions cease?

According to a commission done in 1981, brain death can be determined by the following criteria; unresponsiveness (person does not respond to any external stimulus and cannot communicate with the outside world,) an absence of cerebral and brain stem function (pupils are unchanging, no gag reflex, limbs are flaccid,), nature of coma is known, must rule out hypothermia, drug intoxication and the person is not in shock. Also, you must have 12 hours without an EEG response or other EEG measure. There are also confirmatory things to look at, but these are not required, you can have an EEG with no activity, no cerebral blood flow, and no function in vital brain stem areas. (4) This can be summarized by saying that the brain has to totally cease functioning. If this is the case, then without life support, the body will eventually also cease to function. However, not all cases of brain death are even as cut and dry as the previous description. There is a form of brain death called cerebral cortical death, this is where the cerebral cortex suffers irreparable damage and put the individual in a vegetative state. This state shows arousal, but no conscious awareness of the world around the individual. (3)

In this case of a persistent vegetative state there is little chance of recovery. One documented case had a woman lie in this state for thirty seven years before finally dying. Is the person dead? According to one theory you might assume yes. If you take consciousness as being the criteria for human life, then these people are dead. Defining consciousness as arousal and awareness of the external and internal world, people for whom the cerebral cortex is dead are dead. They have no arousal, no eyelids opening, or arousal is the only rare response they have. According to the legal definition, they are not brain dead, and thus not dead. They have no awareness, no attempts to communicate, no way of recognizing or understanding. (5) The fact that they are not "dead" poses some problems. If you wish to obtain their organs for use in other people, having them stay alive prevents you from acquiring them. Other people die while these vegetables live.

From the perspective of neurobiology this conundrum poses an interesting question. When does the nervous system cease to function? If it were merely the case that we declared a dead nervous system when certain parts stopped functioning, then a person would be dead when they suffered crushed nerves in a hand or leg. That is not the case. We still look at the maintenance functions as indicators of overall functioning. Is one part of the nervous system more important critical to our perception of its functioning? This entire problem is something that is a matter of perception and not a matter of "Truth." Death is not a black and white issue where we can say one is there and one is not there. Our perception of what life is plays a big part in our belief. A neurobiologist feels that life is a functioning nervous system, in part or in whole. Thus people who are still breathing and pumping blood, are alive. Still, even for the neurobiologist, there is a question about when the organism ceases to function. While a nervous system may function in part, even the neurobiologist would claim that it was the whole. Take for example a crayfish whose flipper ganglia have been removed and then are "activated." Nobody would say that they are alive. They are merely performing. They are incapable of action on their own.

Perhaps that is the answer that we are trying to find. Death for a human being is when we are incapable of even initiating action and are merely performing. Our minds no longer think, but our bodies continue working. For the people who love the individual who no longer thinks, the mere fact that something works gives them hope. For people that are in need of an organ transplant the fact that someone no longer thinks and their body is fresh gives them hope. Who is to determine which hope will be dashed? This is a decision that cannot be left to just one individual, and must be thought about by all concerned. Still, the decision must be made and the shadowy world between life and death brought into the light, or thrust into the darkness.

Web References

(1)When is Death

(2)Brain Death: Is That Dead Enough?

(3)Brain Dead, Brain Death

(4)Neurology Carlos Eduardo Reis

(5)A new definition of death based on the basic mechanisms of consciousness generation in human beings