Death

Death has many potential causes: disease, injury, poisoning, among others. Any of these may damage to tissues and organs, and disturb the inner balance that allows vitality (homeostasis). All living creatures die, even if they have no particular affliction. Furthermore, every species has its own typical life expectancy. Humans, for example, don't usually pass the 100-year mark, even when they are generally healthy and living in a secure environment. In humans, similar to most mammals, one can discern a slow deterioration in the body's vitality, which eventually results in death.

Current research aims to discover the cause of the body's natural deterioration upon entering old age. Even though findings are generally inconclusive, several theories have been proposed. One theory proposes that the body's deterioration is caused by genetic reasons, as the human genome contains a self-destructive mechanism that kicks off after a specific length of time. Another theory suggests that there is a limit on the rate of cell division which ultimately leads to cell demise (see Telomere).[2] However, many studies show that a proper diet and nutrition together with regular physical activity can extend life expectancy.

In third world countries, inferior sanitary conditions and lack of access to medical technology makes death from infectious diseases more common than in developed countries. [citation needed]Predation is a common cause of death for many organisms.

[edit] Determining when death actually occurs

Human remains found in scrub, circa 1900-1910.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, but the development of CPR and prompt defibrillation posed a challenge, rendering the previous definition inadequate. This earlier definition of death is now called "clinical death", and even after it occurs, breathing and heartbeat may be restarted in some cases. Events which were causally linked to death in the past are now prevented from having an effect; even without a functioning heart and lungs, a person can be sustained with life support devices. In addition to such extremes, there are a growing number of people who would quickly die if their organ transplants or artificial pacemakers failed.

Today, where a definition of the moment of death is required, doctors and coroners usually turn to "brain death" or "biological death": People are considered dead when the electrical activity in their brain ceases (cf. persistent vegetative state). It is presumed that a stoppage of electrical activity indicates the end of consciousness. However, suspension of consciousness must be permanent, and not transient, as occurs during sleep, and especially a coma. In the case of sleep, EEGs can easily tell the difference. Identifying the moment of death is important in cases of transplantation, as organs for transplant (the brain excluded) must be harvested as quickly as possible after the death of the body.

Among human beings, brain activity is a necessary condition to legal personhood in the United States. "It appears that once brain death has been determined ... no criminal or civil liability will result from disconnecting the life-support devices." (Dority v. Superior Court of San Bernardino County, 193 Cal.Rptr. 288, 291 (1983))

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. Eventually it is likely that the criterion for death will be the permanent and irreversible loss of cognitive function, as evidenced by the death of the cerebral cortex. All hope of recovering human thought and personality is then gone. However, at present, 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 Determination Of Death Act in the United States). In 2005, the case of Terri Schiavo brought the question of brain death and artificial sustenance to the front of American politics. Generally, in such contested cases the cause of death is anoxia. Oxygen deprivation for roughly seven minutes is sufficient to kill the cerebral cortex.

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.

There are many anecdotal references to people being declared dead by physicians and then coming back to life, sometimes days later in their own coffin, or when embalming procedures are just about to begin. Owing to significant scientific advancements in the Victorian era, some people in Great Britain became obsessively worried about living after being declared dead. Premature burial was a particular possibility which concerned many; inventors therefore created methods of alerting the outside world to one's status: these included surface bells and flags connected to the coffin interior by string, and glass partitions in the coffin-lid which could be smashed by a hammer or a system of pulleys (what many failed to realise was that the pulley system would either not work because of the soil outside the coffin, or that the glass would smash in the person's face, covering them in broken glass and earth).

A first responder is not authorized to pronounce a patient dead. Some EMT training manuals specifically state that a person is not to be assumed dead unless there are clear and obvious indications that death has occurred.[citation needed] These indications include mortal decapitation, rigor mortis (rigidity of the body), livor mortis (blood pooling in the part of the body at lowest elevation), decomposition, incineration, or other bodily damage that is clearly inconsistent with life. If there is any possibility of life and in the absence of a do not resuscitate (DNR) order, emergency workers are instructed to 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 (DOA).

In cases of electrocution, CPR for an hour or longer can allow stunned nerves to recover, allowing an apparently-dead person to survive. People found unconscious under icy water may survive if their faces are kept continuously