I responded to a comment that described the tingling sensations from hitting your funny bone, and then insinuated that a blow to the head would be similar experience but more extreme.
That is just plain false.
I was using it as an example of how trauma can cause nerves to depolarize and stop working.
As others have pointed out, it is far more devastating in the CNS than in peripheral sensory nerves, and HOW we perceive the trauma depolarization is going to be different.
The first thing to assessing impact is understanding WHAT is happening in the body from the trauma.
The trauma to depolarize nerves and make them STOP WORKING is not always that large.
A head blow (boxing or otherwise) can shut down everything in the CNS briefly over wide areas of the brain.
You do not feel anything, or remember anything, since a large area has been affected.
When you strike your head and 'see stars' the area affected is the visual cortex.
Striking it is very likely to be perceived as a visual disturbance.
Strike the area of the brain for hearing and you are likely to perceive sound from the depolarization.
One of the more recent discoveries was that head trauma that results in the cessation of respiration is NOT a death sentence as was previously thought.
If you can get the patient on a respirator and try and limit brain swelling (chemically or surgically or both) the patient may recover.
The brain is acutely sensitive to even minor pressure.
In Multiple Sclerosis the tiny localized swelling in the brain produces most of the symptoms observed, not the actual damage to any single nerve.
The damage from the temporary swelling can become more permanent the longer it is allowed to continue however.
We are talking about the immune system causing swelling around a small section of a nerve.
It can sometimes barely be seen on an MRI because there is a very slight change in the brain density at the site.
The CNS is remarkably easy to disrupt, but it is not always repeatable since the damage is rarely repeatable and every persons brain is slightly different.
The 'areas' that have been mapped as performing different tasks and functions are not hard and fast, just general 'areas' that in a number of patients have appeared to create similar symptoms.
Larger functions can be mapped (left side of brain controls right side of body) but mapping a particular muscle innervation to a spot on the brain is not nearly as sharp a boundary.
It took any years for effective treatment for bacterial meningitis to be developed.
The mortality rate in infants was 80%.
Antibiotics would kill off the bacteria, but the infant died 24-48 hours later from brain swelling (uncontrolled it can force the medulla of the brain through the base of the skull and suppress respiration).
Finally methods were developed to suppress the immune system to prevent the swelling, and the mortality rate dove to less than ~20%.
For self defense the brain is still a small target, inside a nice bone skull for protection.
You need to not just get past the bone, but do enough damage over a wide area.
Damage a less important area or small area and not much may happen.
