by Folk wisdom says that it is the only certainty we have in life, but at the same time it remains one of humanity’s greatest mysteries: death. The answers to what might be “on the other side” are given by religion or philosophy, human cultural constructs, but for the last moments of life, it is science that explains.
What happens when we die?
Neurologically, at the moment of death the central nervous system ceases to function permanently and permanently. The mechanisms activated in the body vary, which differ according to how each person dies.
In the case of slow death, such as multiple organ failure, research says the human body tends to prioritize the brain, heart and kidneys.
In CNN Brasil, Fernando Gomes, university professor and professor at the Hospital das Clínicas de São Paulo, explains that, in these cases, “the other organs suffer, until they all stop, as if it were a bus that ‘crashes into a pole’ . .
In cases where death does not initially involve the brain, it is different. “When a patient dies of non-neurological causes, the regulation of blood pressure in the vessels of the head is slowly lost, with a decrease in the supply of oxygen and glucose. As a result, neurons undergo cell death due to hypoxia, which is the lack of oxygen, and ischemia of neuronal cells occurs. They diffuse their contents into the environment around the cells and stop working,” says Felipe Chaves Duarte, a neurologist in São Paulo.
After the neurons die, depending on the type of medical care received, other organs can continue to function with the use of drugs and devices such as ventilation.
This condition, diagnosed by doctors, is called brain death. The patient loses consciousness, cannot think or receive stimuli from the environment. He ceases to exist as a human being and the organs outside the nervous system continue to function artificially,” explains the doctor.
Cells do not all die at the same time.
As experts explain, different cells in the body die at different rates and progressively. The order depends on the cause of death. In cases of brain death, organs can be kept functioning for several weeks.
In cases where the heart stops beating, “organs such as the lung can remain viable for transplantation for up to 4 hours and organs such as the kidney for up to 36 hours, provided they are kept in appropriate containers,” explains Felipe Duarte.
In the brain, some cells can survive hours after the patient is declared dead, but they cannot sustain brain activity on their own. Remember that neurons are the first cells in the body to die, they don’t last more than five minutes without oxygen supply, without irreversible damage.
On the other hand, corneal epithelial cells are the ones that last the longest without oxygen, they can last up to six hours and remain viable for transplantation during this period.
What can we feel at the time of death?
Several studies have tried to find the answer to what we feel when we die. A paper published in the journal Resuscitation in 2014 interviewed 101 people who had suffered a cardiac arrest and survived. Half said they did not remember anything, and 40% had memories, such as people, plants, or an emotion and fear. Of the respondents, 9 indicated what would be compatible with near-death experiences.
In another study, experts recall, published in Frontiers in Aging Neuroscience, images of a brain were analyzed one hour after the patient’s death. At that time, the moments before and after death were recorded, confirming an oscillation of gamma waves and a high rate of electrobrain activity, with a frequency of more than 32 Hertz.
“This points to a possibility for the idea that at the moment of death, before consciousness goes away, we have a moment of superconsciousness, in which very relevant memories, mostly emotional ones, are triggered, as if your life were in a movie. You can’t prove it, but from an electrical point of view it makes sense,” explains neurosurgeon Fernando Gomes.
So what are near-death experiences?
Near-death experiences (NDEs) occur with a reduction in blood flow to the brain, which primarily affects the parietal lobe. It is not enough to cause a stroke, but some level of consciousness is maintained, to the point where there is some kind of memory of the experience.
It’s like that ‘light at the end of the tunnel’ and a feeling of well-being or calmness, probably caused by the release of neurotransmitters like, for example, opioid derivatives, endorphins and others.”
With the loss of functions in different areas of the brain, different sensations can occur, and one possibility is that, through the activation of areas of the midbrain, there is a release of noradrenaline, which is involved in a response to fear or stress, and which is linked with areas of the brain that regulate emotions such as the amygdala or the hippocampus.
“A possible explanation for the sensation of being in a tunnel of light occurs when there is a drop in pressure in the vessels that supply the retina, which occurs during cardiorespiratory arrest,” concludes Felipe Duarte.
