The human head can remain conscious for up to 7 seconds (between 3-5 seconds). A study was done on prisoners that would go before the blade. They told the prisoners simple commands, blink, wink close eyes etc after their head was cut off. Indeed they did such commands to over 100 different prisoners and proved it true.
Not for more than a split second. As soon as the blood pressure drops, which would be nearly instantaneous, there would be a blackout. As unpleasant as it sounds, clean decapitation is actually a pretty merciful death.
The cerebellum
The part of the brain that controls conscious activities of the body is the pituitary gland. It is usually located at the base of the skull.
The brain is the endpoint of all conscious sensations from limbs
The reticular system
Without oxygen the brain loses consciousness in a few seconds. 6-8 minutes and you've got permanent brain damage, but it wouldn't matter because in a vacuum the lack of pressure would cause your blood to boil, killing you instantly.
Cerebrum
the sub conscious mind
In the brain but not in any exact place as it is an epiphenomenon of all the nerve connections throughout the brain.
cebrum-parietal lobes
These muscles are called involuntary muscles. They are found in all hollow organs such as your digestive tract.
There are no pain or motion neuroreceptors in the brain proper. This is what allowes the patient to be kept conscious during many neurosurgeries.
Mind is more like a human characteristic due to human brain that allows humans to memorize, think and do other things including being conscious. Consciousness is all about being aware of whatever that is outside or within oneself.