Why do people get knocked out?

[sonicated909]

When people receive a big blow to the head, such as a punch, their whole body freezes and they naturally hit the floor. Why is this?

What does the brain do, or does not do, when this happens? Why do most muscles in the body, such as the legs, go limp but the heart carries on? (unless in extreme circumstances)

[Ouisch]

I'm not a doctor, but I would imagine it's because such a strong blow to the head causes the brain to sort of "slosh" around within the skull, getting bruised and battered.  The outermost part of the brain, the cerebrum, controls voluntary muscle movement, and that is the area that gets crunched in most head punches.  The brain stem, located at the top of the neck and underneath the brain, is the area that controls heartbeat and respiration.

[El D]

Essentially thats correct. The head is moved so violently that the brain bashes into the inside of the skull and shuts down to prevent damage. This is why rotational blows to the head offer a greater chance of a ko i.e. straigh blows cause little head movement.

[undercovers]

i was always under the impression that unconsciousness was not fully understood e.g. they know the situations in which it occurs but don't understand exactly why. I agree with El D that rotational blows tend to knock people out more but have always put this down to the thin protective layer of the skull at the side of the head compared to the front. As for shutting down the brain to prevent damage, I find this unlikely as surely more damage will occur when under attack if you become unresponsive. But would be very interested to see some references or further explanation El D

[Scarlett]

I think I read somewhere that the brain doesn't "shut down" as such, but it stops certain bits from operating for a minute- like when you faint. The brain puts all it's efforts into repairing the injured or stressed body, so (like when you are asleep), stops the body from moving or making itself worse, conks it out, and sorts it out from there.

[pjm007]

You sometimes see on films, people getting karate chopped on the top of the back, (just below the back of the neck) thus, rendering the victim unconscious. How is that possible ? and does it really work ?

[Impret-Sir]

The point about heart muscle is that it has a special property not shared by any other type of muscle in the body. That is, it has a contractile reflex that is not dependant upon signals from the brain. If this were not the case then people with spinal cord injuries would die because their heart would stop. This also explains why people who are called "brain stem dead" still have a pulse. The medulla oblongata, or "brain stem", does not control the heart rate, but it does control the respiration rate, by monitoring carbon dioxide levels in the blood, thus, if your CO2 levels go up, it commands the respiration rate to increase, and vise versa.

[ian22]

I am not a doctor, but unfortunately have some personal experience. I am told that the brain moves when the body is moving and then suddenly stops as in an auto accident or hit against an object....and yes, rotational force, can cause the most damage. When this has happened to me, I have had associated amnesia and don't remember anything about the incident except what I have been told by doctors.