Here's a nice little description.....a bite From a Sydney Funnel Web spider....[deadliest 8 legged thingie]...
Remind me not to get bitten...
Symptoms and signs of envenomation include:
Numbness around the mouth and spasms of the tongue
Nausea and vomiting, abdominal pain, acute gastric dilatation
Profuse sweating, salivation, lacrimation, piloerection
Local and generalized muscle fasciculation and spasm, commencing in facial tongue or intercostal muscles, and including trismus, which may necessitate paralysing the patient with muscle relaxants in order to manage the airway
Dyspnoea
Confusion, irrationality, coma which may persist in the presence of normalized ventilation, oxygenation and blood pressure, and may be related to raised intracranial pressure
Hypertension, vasoconstriction, tachycardia and cardiac arryhthmias  ? related to release and subsequent depletion of neurotransmitter
Widely dilated pupils, which may be fixed
Acute non-cardiogenic pulmonary oedema
Later, the severely envenomed patient may develop progressive hypotension and apnoea.  These features may relate to depletion of neurotransmitter.