Editing Australian funnel-web spider (section)

===Toxins===
Many different [[toxin]]s are found in the venom of ''Atrax'' and ''Hadronyche'' spiders. Collectively, these [[spider toxin]]s are given the name atracotoxins (ACTX), as all these spiders belong to the family Atracidae. The first toxins isolated were the [[Delta atracotoxin|δ-ACTX toxins]] present in the venom of both ''A. robustus'' (δ-ACTX-Ar1, formerly known as [[robustoxin]] or atracotoxin) and ''H. versuta'' (δ-ACTX-Hv1a, formerly known as [[versutoxin]]). Both of these toxins produce the same effects in monkeys as those seen in humans, suggesting that they are responsible for the physiological effects seen with crude venom.<ref name="ClinExp2002-Nicholson"/>

[[File:Atrax robustus.jpg|thumb|Female Sydney funnel-web spider (''A. robustus'') in a warning posture]]
These toxins are thought to induce spontaneous, repetitive firing and prolongation of action potentials, resulting in continuous acetylcholine neurotransmitter release from somatic and autonomic [[presynaptic]] nerve endings. This leads to slower [[voltage-gated sodium channel]] inactivation and a hyperpolarizing shift in the voltage-dependence of activation. This in turn inhibits neurally mediated transmitter release, resulting in a surge of endogenous [[acetylcholine]], [[noradrenaline]], and [[adrenaline]].<ref>{{cite journal |vauthors=Harris J, Sutherland S, Zar M | title = Actions of the crude venom of the Sydney funnel-web spider (''Atrax robustus'') on autonomic neuromuscular transmission | journal = Br J Pharmacol | volume = 72 | issue = #2 | pages = 335–40 | year = 1981 | pmid = 6260279 | pmc = 2071519 | doi=10.1111/j.1476-5381.1981.tb09132.x}}</ref>

Although extremely toxic to primates, the venom appears to be fairly harmless to many other animals. These animals may be resistant to the venom's effects due to the presence of [[Immunoglobulin G|IgG]], and possibly cross-linked IgG and [[IgM]] inactivating factors in their [[blood plasma]] that bind to the toxins responsible and neutralise them.<ref>{{cite journal |vauthors=Sheumack D, Comis A, Claassens R, Mylecharane E, Spence I, Howden M | title = An endogenous antitoxin to the lethal venom of the funnel web spider, ''Atrax robustus'', in rabbit sera | journal = Comp Biochem Physiol C | volume = 99 | issue = #1–2 | pages = 157–61 | year = 1991 | pmid = 1675965 | doi = 10.1016/0742-8413(91)90093-9}}</ref>

The female's venom was thought to be only about a sixth as potent to humans as that of the male's.<ref>{{cite journal | author = Wiener S | title = The Sydney funnel-web spider (''Atrax robustus''): II. Venom yield and other characteristics of spiders in captivity | journal = Med J Aust | volume = 46 | issue = #2 | pages = 678–82 | year = 1959| pmid = 13844638| doi = 10.5694/j.1326-5377.1959.tb129426.x | s2cid = 2131853 }}</ref><ref>{{Cite book |last=Sutherland |first=Struan K. |title=Australian Animal Toxins |publisher=Oxford University Press |year=2001 |isbn=978-0195506433 |location=Melbourne |language=EN}}</ref> The bite of a female or juvenile may still be serious, but considerable variability occurs in venom toxicity between species, together with assumed degrees of inefficiency in the method of venom delivery.