The Brazilian wandering spider is considered the most poisonous spider in the world. Six millionths of a gram (about 1/100 the weight of a human leg hair) is enough to kill a mouse (WHO DOES THESE STUDIES?). It kills the mouse (or you) by injecting the toxin PnTx2-6 which stops your nerves from to talking to your muscles by blocking calcium channels. Changes in calcium concentration within your muscle cells by the opening of these channels is what signals the proteins in the cell to pull on each other causing muscle contraction. This is pretty important for muscles like your diaphragm because without nerves activating this muscle you stop breathing. You need to breath to live (true fact).
But in a interesting turn of events while your diaphragm stops working your penis starts to work (if you have one). No it isn’t that you have an odd fetish for spiders, the toxin also happens to cause vasodilation or the widening of your blood vessels. You see an erection works a lot like a party balloon, it is inflatable, but it isn’t inflated by air it is inflated by blood. Both Viagra and PnTx2-6 cause a buildup of a signalling molecule (cGMP) which signals the dilation of the blood vessels causing more blood to flow in and the party balloon to inflate. Researchers are now investigating whether really low concentrations of the spider toxin could be the next Viagra.