Man's good relations with land, fellow beings, and charming and useful things keep a person alive and trun this world into a paradise for him.
Energy. The energy within us is what keeps us alive.
Where does this energy come from?.. Well, different cells in the body have their own ways of getting it. The simplest of them all is oxygen.
Why is oxygen needed?.. Every cell of the body needs it to carry out various oxidative processes that lead to the breakdown of glucose. Glucose which comes from food, is our fuel. We need a constant supply to keep functioning. Glucose gives us energy.
How?.. Cos cells break down glucose in the presence (or absence.. Sometimes when oxygen reaching the cells of that tissue is inadequate) to release ATP. Now wht is ATP?.. ATP or adenosine triphosphate is the energy currency of any cell. It has 2 high energy bonds. When any redox process breaks any of these bonds, large amounts of energy is released. Around 30 kilo joules of energy is liberated when one adenosine triphosphate is converted to it's diphosphate. This ADP can further be broken down to release adenosine monophosphate, along with another 30 kJ of heat. In one cycle of aerobic respiration by one cell 38 ATP molecules are generated. Besides atp there are other such energy storage molecules like nadp, nad, etc.. Which are also generated in that cycle.
So, if you are breathing, all the cells in your body are breathing. Which means that there is continuous breakdown of glucose, continuous generation of ATP, which can be broken down by other cells of the body for energy, as and when required. So there is continuous production and utilization of tremendous amount of energy, in our bodies.
What happens when we die?.. Death due to different reasons is due to alterations in the body physiology. These alterations slowly accumulate to ultimately cause death. Death is a process.
What triggers it?.. Whatever might be the initial trigger factor, death occurs when oxygen supply is cut off from the vital tissue for a time period of duration longer than what the cells can endure. Be it a heart attack or in case of drowning or sleep apnea in old age.
How?.. Simplest example.. Take heart attack. One of the most dreaded conditions which takes away innumerable lives every year.
What happens in a heart attack?.. We eat all sorts of fatty junk food, drink to our hearts content, kill our poor liver with the massive amounts of alcohol intake we do at a regular basis, leisure time is spent sitting on a chair watching TV or a tablet. Our work environment is also such that we don't need to move around much. What happens over the years is that an unhealthy lifestyle leads to buildup of bad cholesterol which gets deposited in the walls of the vessels and narrows it, hardens it.. To such an extent that one day it gets clogged. The day it clogs the coronary arteries supplying the heart.. The part of the wall being supplied by that artery gets no oxygen. If the supply is restored by any means within half an hour. Heart muscles are happy and alive and all pumping, again. If not, there is ischaemia of that region of heart muscles. If that area is too large, pump failure occurs. No pump = feeble pulse. Body organs don't get fresh oxygen. The neurons of our nerves is the most sensitive to them all. Don't give it oxygen for 5 minutes.. It dies. Once it dies, there is no repair. Once the nerve of the center in the brain that control heart rate and breathing are lost, person dies. That is why it is very very important that a newborn baby cries immediately after delivery.. Or at least within 5 minutes. Crying causes his lung alveoli to open up and forces the lungs to do their job. Cos if the time period extends for more than 5 minutes, permanent brain damage starts. A child who cries after 5 minutes is mentally retarded for life. A baby who doesn't cry for 10 minutes, is lost.