When You Die, How Long Until You're Actually Brain Dead?

This question originally appeared on Quora. Answer by Mehul Singh Saini.

The speed of nerve impulses varies enormously in different types of neuron. The fastest travel at about 250 mph, faster than a Formula 1 racing car!! Neurons with myelin conduct impulses much faster than those without myelin.

The human brain is quite a heavy organ weighing around 1400 grams or 1.4 kg. But we never feel a 1.4 kg weight on our head giving us headache. Why? Inside the skull, the brain is suspended in Cerebrospinal fluid, effectively floating in liquid and the buoyant force on the brain reduces the apparent weight of the brain by almost 1 kg.

The human brain arises from the germ layer called ectoderm that gives rise to nails, hairs, enamel of the tooth, sensory epithelium of the ear, nose and eye, skin.

The brain has a part called the hippocampus. The structure’s shape resembles that of a sea horse, hence the name. It is located in the inner region of the temporal lobe and forms part of the limbic system, which is particularly important in producing emotions.

The function of the hippocampus is to form long term memories and any damage to the hippocampus hampers this process. This is basically what we have seen in the movie Ghajini (or Memento from which Ghajini was inspired).

The protagosnist suffers from a condition called anterograde amnesia (aka short term memory loss) that happens due to damage to the hippocampus where the brain is unable to commit any information to long term memory.
Amyotrophic Lateral Sclerosis

Amyotrophic lateral sclerosis (ALS), sometimes called Lou Gehrig's disease, is a rapidly progressive, invariably fatal neurological disease that attacks the nerve cells (neurons) responsible for controlling voluntary muscles.

The famous scientist Stephen Hawking suffers from this disease but his is an unusual case as he suffers from a rare sub-type of ALS that is non fatal.

We use 10% of our brain is one of the biggest myths about the human brain. You can't assign a percentage to how much part of your brain is currently active.
Though the brain is only 2% of the body weight it gets whopping 20% of the blood supply of the blood pumped by heart.

There are 100 billion neurons in the brain and the collective electricity generated by them is sufficient enough to power a small light bulb.

For a machine as fast and advanced as the human brain, it has shockingly very low energy requirements - 20 Watts. If we built a supercomputer with the same computing abilities of the human brain it would require at least 10 megawatts to operate. How Much Power Does The Human Brain Require To Operate?

After the death of Albert Einstein his brain was stolen by the coroner who was doing autopsy on his dead body. Thomas Harvey, the pathologist on call at the Princeton Hospital took out Einstein's brain and kept it with him for many years before returning the same to the hospital. The Tragic Story of How Einstein's Brain Was Stolen and Wasn't Even Special

According to a BBC documentary titled Secrets of Superbrands a team of UK neuroscientists scanned the brain of an Apple fan and discovered that Apple products stimulate the same part of the brain as religious imagery does in people of faith. The documentary also likens Apple Stores to cathedrals. Apple stores often feature stone or other types of austere, simple flooring like a church with products mounted on pedestals like individual altars.