“Anaesthesia” means without feeling, and is what is necessary when someone has to undergo a surgical operation or some other painful procedure on the body. “Analgesia” means without pain.
The part of the body that controls consciousness, feeling, pain and movement is the nervous system. Anaesthesia involves the introduction of chemical substances called anaesthetics into the body, and these numb that part of the nervous system to which they are applied. If for example they are introduced into the bloodstream they will reach the brain itself, producing unconsciousness.
Alternatively they can be applied to the spinal cord by way of a spinal or epidural injection, producing loss of sensation to the lower part of the body, or applied directly to the large nerves, producing loss of sensation to the part of the body supplied by that nerve.
Read more:
The Journey
Will your anaesthetic work?