 |
Business | Industries | Finance | Tax |
| Index: > A B C D E F G H I J K L M N O P Q R S T U V W X Y Z |
|
|||||
| First Prev [ 1 2 3 ] Next Last |
Death is a term that can refer to either the termination of life in a living system, or the state of that organism after that event. A common perception of death is a grim reaper or the color black.
Biologically, death can occur to wholes, to parts of wholes, or to both. For example, it is possible for individual cells and even organs to die, and yet for the organism as a whole to continue to live; many individual cells can live for only a short time, and so most of an organism's cells are continually dying and being replaced by new ones.
Conversely it is also possible for the organism to die and for cells and organs to live and to be used for transplantation. In the latter case, though, the still-living tissues must be removed and transplanted quickly or they too will soon die without the support of their host. Rarely, cells can be immortal as in the case of Henrietta Lacks HeLa cell line.
Irreversibility is often cited as a key feature of death. Accordingly by definition it would not be possible to bring an organism back to life; if an organism lives, this implies that it has not died earlier, even if that seemed the case. Nonetheless, many people do not believe that death is always and necessarily irreversible; thus some have a religious belief in bodily or spiritual resurrection, while others have hope for the eventual prospects of cryonics or other technological means of reversing death.
Some biologists believe that the function of death is primarily to permit the operation of evolution.
By far the most important sort of death to human beings is human death. Thinking about human death raises a number of questions.
First, how can we identify the exact moment at which death has occurred? This seems important, because identifying that moment would allow us to put the correct time on death certificates, make sure that the deceased's will is enacted only after the deceased is truly deceased, and in general guide us regarding when to act as one should act toward a living person and when to act as one should toward a dead person. In particular, identifying the moment of death is important in cases of organ transplant, as organs must be harvested as quickly as possible after death.
Historically, attempts to define the exact moment of death have been problematic. Death was once defined as the cessation of heartbeat ( cardiac arrest) and of breathing, for example, but the development of CPRSurvival skills For other meanings of CPR, see CPR (disambiguation). This article details Cardiopulmonary resuscitation (CPR) procedure. It is intended as a reminder for those with previous CPR training. It is not intended as a "teach yourself CPR" guide. and early defibrillationDefibrillation is a medical technique used to counter the onset of ventricular fibrillation, a common cause of cardiac arrest, and ventricular tachycardia, which sometimes precedes ventricular fibrillation but can be just as dangerous on its own. The equi posed a challenge: either the definition of death was incorrect, or techniques had been discovered that really allowed one to reverse death (because, in some cases, breathing and heartbeat can be restarted). Generally, the first option was chosen. (Today this definition of death is known as " clinical death".)
Today, where a definition of the moment of death is required, we usually turn to " brain deathBrain death is defined as a complete and irreversible cessation of brain activity. Absence of apparent brain function is not enough; evidence needs to be available that the condition is irreversible. Traditionally, death was defined as the cessation of al" or "biological death": people are considered dead when the electrical activity in their brain ceases. It is presumed that a stoppage of electrical activity indicates the end of consciousnessConsciousness is a quality of the mind generally regarded to comprise qualities such as self-awareness, sentience, sapience, and the ability to perceive the relationship between oneself and one's environment. In common parlance, consciousness denotes bein. However, those maintaining that only the neo-cortex of the brain is necessary for consciousness sometimes argue that only electrical activity there should be considered when defining death. In most places the more conservative definition of death (cessation of electrical activity in the whole brain, as opposed to just in the neo-cortex) has been adopted (for example the Uniform Definition of Death Act in the United States).
Even in these cases, the determination of death can be difficult. EEGs can detect spurious electrical impulses when none exists, while there have been cases in which electrical activity in a living brain has been too low for EEGs to detect. Because of this, hospitals often have elaborate protocols for determining death involving EEGs at widely separated intervals.
Medical history contains many anecdotal references to people being declared dead by physicians and coming back to life, sometimes days later in their own coffin or when embalmingEmbalming in most modern cultures, is a process used to temporarily preserve a human cadaver to forestall decomposition and make it suitable for display at a funeral. It has a long history, and other cultures had embalming processes that had much greater procedures are about to get underway. Stories of people actually being buried alive (which must assume embalming has not occurred) led at least one inventor in the early 20th Century to design an alarm system that could be activated from within the coffin.
Because of the difficulties in determining death, under most emergency protocols, a first responder is not authorized to pronounce a patient dead; some police training manuals, for example, specifically state that a person is not to be assumed dead unless there is clear and obvious indications that death has occurred, such as decapitationDecapitation or beheading is death caused by removing a living being's head. This may be done by hand with an axe, sword, or knife, or by guillotine. In rare cases it may also be the result of an explosion, automobile accident or other violent injury. or extreme damage to the body. If there is any possibility of life and in the absence of a do not resuscitate order, emergency workers must begin rescue and not end it until a patient has been brought to a hospital to be examined by a physician. This frequently leads to situation of a patient being pronounced dead on arrival.
It might also be worthwhile to entertain the possibility that death does not occur at a particular moment, but unfolds as a process over a period of time. Perhaps, in the end, it is not terribly meaningful to speak of "the exact moment of death".
| Politics | Business | Finance |
 |
 |
 |
|