While sitting on a rock next to a berry bush, I thought I would have a tasty snack. Realizing I wasn’t sure what type of berry it was, I decided not to eat it due to its possible poisonous nature. Then I wondered what poison is and how is works. Why are some things immune from poison and other things are not?
Actually, there’s more than one type of poison. Arsenic is poisonous, but snake venom doesn’t contain arsenic. And carbon monoxide is poisonous, but it’s not the same as rat poison. Different kinds of plants contain different poisons, so there’s no simple answer to your question.
-Ben
As a generalisation, I’d say anything poisonous will suppress any or all vital bodily functions, or create a violent auto-immune reaction. As Ben said, there are many chemicals out there with varying effects on the human body.
Leave the unknown berries alone.
I think most of them work by somehow ‘turning off’ or inhibiting certain critical biological/chemical functions.
On the topic of snake poison… they work in 2 major ways. One makes it so you can no longer breath voluntarily… thus, you fall asleep, you suffocate. The other basically tells your blood to clot, and as you can assume, the result isn’t pleasant.
Breath involuntarily, I mean.
The encyclopedia is your friend. (In this case, the Columbia Encyclopedia.)
Many of the most lethal poisons interfere with a vital metabolic process. Carbon monoxide binds with hemoglobin, 210 times as strongly as oxygen, so that the victim dies from a lack of oxygen. Military nerve gases attack an enzyme, cholinesterase, which is crucial to the transmission of nerve impulses throughout the body. Many animal venoms are nerve agents (neurotoxins), or attack red blood cells (hemotoxins and hemolysins).
Other sorts of poisons are corrosives, such as mustard gas, which burn and blister; heavy metals (lead poisoning or mercury poisoning); and radiological poisons, which ionize the atoms in tissues and disrupt cellular metabolism. Uranium or plutonium can cause both heavy metal and radiological poisoning.
Since many poisons work by interfering with specific metabolic processes, animals can evolve immunities to them by developing reconfigured metabolic pathways that lack the specific vulnerability the toxin exploits, or by developing metabolic processes that act to neutralize the effects of the poison. No cite for that one; I just made it up, but it sounds good and it’s probably true.
All posions work differently. The most available resource i have is on snake venom so i’ll use that as an example. A good majority of snake venoms are proteins and enzymes that interfere with neurons.
I’m “translating” this from a fairly large toxicology text so i apologize in advance to any bit of information that isn’t as accurate as it should be. I think i have a grasp on it, but i’m still not fluent in Toxicspeak.
A neuron is a nerve cell that conducts a charge through the body. Many nerve cells connect and an impulse travels down them and stimulates the action.
In each nerve cell there is an uneven amount of sodium or potassium (sometimes calcium)on one side of the cell. Each nerve has a gate in it. When it gets stimulated the gate opens to allow Na and K to move in and out of the neuron to reach a (relatively) equal amount on both sides. When this happens the current runs through (releases a specific neurotransmiter and) it and activates whatever it activates.
Certain nerves control certain functions of the body. Lets take the neuron which releases the nuerotransmitter ACH (it controls muxcle movement) What a certain toxin would do is go through the body and find all of the Neurons that control the release of this neurotransmitter. It then can(depending on the toxin) keep the “gate” in the neuron open, or keep the gate closed. Either way If the cell has no way of building up or releasing the K or Na, then no charge can go through. If no charge can go through, then Whatever muscle is supposed to get the order to release or contract won’t work. You can see how this would be bad for certain organs such as the heart.
This is the best i can do until an expert makes his way to the thread.
IANAT, but most of the poisons I can think of can be categorised by their ‘target organ’, which in addition to the usual liver (eg paracetamol/acetaminophen) and kidneys, could be the brain/nervous system. Toxic plant alkaloids (chemicals whose name often ends in ‘ine’ or ‘amide’) often affect the nervous system. If this is the case, there’s a good chance that death would result from the nervous system being unable to adequately control breathing. Assuming that the nervous system would start working normally again when the poison was removed, and that the poison could be broken down into harmless substances, death could be prevented by using forced respiratory support. It’s also possible that there is no specific target organ and that the poison is a cytotoxin - it kills cells without too much regard for what the cells are or what they do. Corrosives (acids, chlorine), cyanides and ricin (from castor beans) fall into this category.
There are also certain trends common to what the poisons do at their target site. Off the top of my head, a poison might:
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React with an important nutrient, enzyme or other chemical in the body to produce a harmless but useless substance. The body would then be deprived of the important chemical, and some function would be impaired. For example, carbon monoxide reacts with oxygen-carrying haemoglobin to yield the non-oxygen-carrying carboxyhaemoglobin. Fluorides steal the body’s calcium to form calcium fluoride, and I don’t know but presume this explains why calcium fluoride is less dangerous than sodium fluoride or hydrofluoric acid.
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Imitate a legitimate substance that belongs in the body (it may even be the exact same substance, just artificially introduced in excess amounts). This could trick some body function into performing excessively or insufficiently (eg hormones that change body temperature or heart rate).
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Imitate a legitimate substance well enough for the body to collect and store it as if it were the real thing, but not well enough to actually do the job of the substance it is imitating. I think some heavy metals, including lead, can be stored in place of calcium. With radioactive metals the radiation is made more dangerous, because it is stored near to the tissues where it can do more damage.
Which one of these 3 (if any) is related how an antidote might work. With 1) you can supply more of the nutrient that is being depleted or blocked (eg calcium gluconate for fluorides, vitamin K for warfarin). With 2) there is usually another corresponding substance in the body that does the opposite thing that you can use. 3) can be difficult to treat.
Whilst I’m aware that this is somewhat simplified anyway, and corrections would be welcomed, no matter how trivial (should I not be saying that? 
The poisons in plants (like there might have been in your unidentified berries) are often alkaloids, which can be harmful in a number of different ways, but usually, they do things like causing muscles to relax, including the heart muscles, which would be a bad thing.