Or any other poison that causes “instant death”. I am unfamiliar with medical topics, and the only explanations that come to mind seem rather “mechanical” (for lack of a better word) like internal hemorrhaging or swelling-induced airway obstruction. But even that doesn’t seem “instant”.
Also, I’ve read that some kinds of poisons like sarin “attack the nervous system”, but I’m unclear how that actually works.
Can anyone explain, or point me to a site with a decent explanation for a layman?
DHR
IIRC, cyanide, being a very good ligand (sticks to metals), takes over all the available sites in haemoglobin normally reserved for diatomic oxygen and carbon dioxide. Respiration stops. You die.
So I assume that cyanide molecules make their way into the bloodstream either through the mouth or the stomach and attach themselves to red blood cells, and the red blood cells thus don’t have room to carry oxygen when they next swing by the lungs. Does that lead to instant–i.e., within seconds–death? I thought you’d have to suck down carbon monoxide at least for a couple of minutes in order to get the same effect. Why does cyanide act so much more quickly?
Not that I doubt your answer–I am just curious about the actual sequence of events.
DHR
"The cyanide ion forms a reversible complex with the respiratory cytochrome oxidase enzyme system, an enzyme system essential for oxidative processes within cells. This results in impairment of cellular oxygen utilisation. The central nervous system, particularly the respiratory centre, is especially susceptible to this effect and respiratory failure is the usual cause of death. "
Cyanogen Agents and military uses.
Another site that is much better on the technical stuff Toxicity, Cyanide
“seconds to minutes for inhalation/intravenous …minutes to several hours for skin absorption”
Thanks for the links, funneefarmer.–DHR
So I was talking bollocks then. Teach me to post drunk. No it won’t.
The effects of cyanide on human tissues vary considerably depending upon the time frame or type of dose. If you ingest cyanide, the tissue effect is a combination of the ions interfering with oxygen transport OUTSIDE of the cells by poisoning hemoglobin, and also by affecting electron transport INSIDE the cell, specifically inside the mitochondria, by poisoning the cytochromes.
But gaseous inhalation is supposed to work much quicker because it blocks the oxygen transport system fairly rapidly. This is why gaseous cyanide is such a killer, compared to the solid form (which still isn’t a bouquet of roses).
But Sarin and other organo-phosphates are a heck of a lot cooler in their action. Most of these “nerve gasses” act by blocking an enzyme in your synapses that clean out a neurotransmitter called acetylcholine.
The autonomic nervous system has been logically divided into two subsystems called the symapthetic and the parasympathetic nervous systems. The former for “fight or flight,” the latter for “rest and digest.” As it happens, the parasympathetic nervous system uses mostly cholinergic compounds (acetylcholine being the biggy). The sympathetic uses the catecholamines like epinephrine/adrenaline, if you can remembr back to that bitching heart stick in Pulp Fiction.
The part of the nervous sytem that you can actively control by thought also uses acetylcholine, specifically in the neuro-muscular junctions, but we’ll get into that later.
Anyway, a nerve works by puffing out a small amount of neurotransmitter into a small gap, it diffuses across the gap, and then the neurotransmitter is chnaged/destroyed/taken up so that it cannot signal again. The crux of this matter, though, is the speed at which this works. So I must digress somewhat.
When your nerves send signals that change over time, such as “lift one ounce now, okay, now lift one-thousand ounces,” it doesn’t send MORE electricity down the nerve axon, it sends the same usual signal just a lot more often, basically just increasing the frequency of the signal. The gap, or synapse, has to clean itself out before another signal crosses so that the receiving cell can get an idea of the frequency of the incoming signal.
The receiving cell or muscle can therefore say “a few pings per second, I’ll lift gently; a crapload of pings per second, and I’ll give it my all!” Our muscles usually respond to signals that occur around 50-60 Hz, or 50 to 60 times PER SECOND.
Think about that. A puff of acetylcholine has to be spit out, travel across the gap, be received by receptors on the other cell, and excess aceycholine cleaned out of the gap in a time frame quicker than 20 milliseconds if it wants to detect another puff. The enzyme doing the cleaning for acetycholine (acetylcholine esterase) therefore works pretty damn quick.
Now back to nerve gas. If you get a toxic dose of nerve-gas, it knocks out this “synapse scrubber,” and the receiving cell thinks that it is receiving a monstorous signal from the parasympathetic nervous system (essentially it is receiving a signals of infinite frequency). Since the parasympathetic system is responsible for down-regulating heart rate, a really high frequency signal can literally stop the heart. This can be achieved within 3 heartbeats after breathing in a gaseous nerve agent. Also, the sudden drop in blood pressure caused by acetylcholine overload (vasodilation, etc.) also causes immediate loss of consciousness.
Therefore a good whiff of this stuff will kill you before you have a chance to hit the ground, though it really takes quite a while for the organs to shut down and your brain to die from lack of oxygen. It is like cutting the head of a bronotsaurus with a chainsaw. The back end of the bugger may keep walking and crapping for another hour or so, but baby, that is one dead dinosaur.
Acetylcholine overdose is one of the fastest killers known. But this is only in the case of a gaseous dose. If the stuf gets smeared on the skin, it takes quite a bit longer to be effective, and the dose must be substantially larger.
But I did mention the neuro-muscular junction, didn’t I?
Well, if you ingest a sub-lethal dose of nerve agent, it will load into the control points for your muscles. Therefore a small signal to contract actually appears to be a huge signal to contract, since the frequency of the signal is altered.
This is kind of cool when you do this to frogs with drugs like prostigmine, which are really pharmaceutical nerve gasses. The frog will just sit there and look at you, but if you make it hop, it goes fricking airborn like Michael Jordan, and contracts all its muscles extremely hard until it has used up all its muscular energy stores, then it flops over, exhausted. This is because a small hop signal gets amplified to a maximal hop signal, and the muscle never gets the signal to shut off, as there is still a lot of acetylcholine in the synapses, making the muscle think that it is still getting a real contract signal. It only stops when the muscle does not have enough energy to contract any longer (complete fatigue).
Let it rest, then give it another poke to start it all off again. 
People with sub-lethal doses of nerve agent can also progress to this stage. If every muscle in your body fires as hard as it can, you’ll break quite a few bones, including probably your femurs, and suffer like a bitch the entire time.
Maybe I should mention that the neurotrasmitters used for pain aren’t based on acetylcholine, mostly. They aren’t affected at all.
But this affect is really useful for some people who have muscular problems. Lets say a patient has a disease that limits the amount of acetycholine released, or the muscle doesn’t react strongly to a normal dose of acetylcholine. By giving the patient a small dose of this nerve agent, it will amplify their muscle activity. Some patients that are normally bed ridden can use these drugs to actually get up and walk around.
So what do you do to get rid of nerve gas poisoning, or guard against it? You use a drug from the belladona plant called atropine. It actually blocks acetylcholine from activiating cells, so it is a direct inhibitor of acetylcholine effects.
As you probably surmised from where the drug comes from, it’s deadly as heck, too. But if you get some in you right before you get a dose of Sarin, you might live through it.
But you’ll definitely feel like you just watched an Ally McBeal marathon. Every nerve you have is going to be raw and hurting.
Nice explanation, Xenopus. Now the AHC, ARC, and HSUS representatives would like to have a word with you regarding the use of chemical weapons on frogs and the derivation of pleasure henceforth 
Speak for yourself, i’m off to find a frog, i’ve already got the phospene
Has anyone else seen the old Army instruction film where they kill a goat with
nerve gas ? Not a great way to go - we listened to the lectures on preventive measures very, very carefully. Gas warfare sucks.
Oh, and one of the preventive measures (after identifying the gas) is atropin injections, as Xeno says. Of course, the average soldier might have a hard time injecting himself, especially on the battlefield while under chemical attack - so the powers that be issues spring-loaded automatic syringes. First, the spring drives the needle into your thigh (through your uniform and NBC suit), and then it injects atropin with alarming speed. The demo version could fire a jet of water straight across an auditorium… Gas warfare sucks, indeed.
As to the speed of nerve agents: We were trained to don NBC masks in 9 seconds - easy when standing in ranks, not so easy when lying in the mud, not at all easy inside an APC designed for fewer people.
Ehm - Xenopus, what exactly are you a student of ?
Norman
Be in time, mask in nine ;).
Oh those days of cooking alive in the back of an APC in full NBC kit. Not fun. Me trying to run in full NBC kit plus weapon, laughable. Hello, MO, there seems to be a problem with my respirator canister, there’s no freakin’ oxygen filtering through!!
Just a minor side note. IIRC the ‘tylenol’ poisonings that started the tamper-proof packaging used potassium cyanide in powder form. The person that ‘planted’ the adulterated capsules had to have done so a VERY short time before his/her victims bought the bogus medicine and ingested it because even the powdered form would eat through the plastic capsules in a couple of hours. Pretty nasty stuff.
What do you want for Christmas, Crow? I want to decide who lives and who dies!
Satchmo, have you ever used potassium cyanide? It’s a perfectly stable crystalline white powder. It is not corrosive. At least the stuff we have isn’t.