Cobras belong to the sub-group of snakes known as
elapids; there are over 270 species of cobras and their relatives. An elapid's venom contains postsynaptic neurotoxins that spread rapidly in its victim's bloodstream, causing respiratory failure and, eventually, death.
Cobra venom is an example of a molecule that prohibits the interaction of acetylcholine molecules (transmitted from nerve endings surrounding the diaphragm muscle) with the receptor sites on the diaphragm muscle. (See the section on
Human Respiration for more details). It binds to the receptor sites, blocking them from interacting with acetylcholine molecules. Even worse, the venom molecule will not immediately break down and vacate the receptor site, effectively removing the site from active duty.
It has been determined that even if only 75 to 80% of the receptor sites on your diaphragm become blocked by venom, you will cease breathing. With cobra venoms, this process can take as little as 30 minutes. The only way to counteract the effects of cobra venom (or most other poisonous snake venoms) is to inject the appropriate antivenom shortly after the bite occurs. If antivenom is unavailable, your life can still be saved by putting you on an artificial respirator until the paralysis of the diaphragm muscle wears off.