MagnusMallard

Intense physical pain may be alleviated by hormones, such as adrenaline, which can supersede the pain. Some shark attack victims say that shark bites are not intensely painful as a result of the shock that overrides them. With respect to taking a bath in, say, sodium hydroxide, the limit seems to be the point at which the neurones and pain receptors in the skin have been destroyed. It's probably more likely that the person subjected to this incredible pain passes out - if the person doesn't, the pain can only escalate until death.

Veins carry blood back to the right ventricle, via the right atrium; this deoxygenated blood is pumped to the lungs via the pulmonary artery. This blood is then re-oxygenated and pumped to the left ventricle, which in turn pumps oxygenated blood to the rest of the body. When a vein (or veins) are blocked, the blood supply is restricted not only to the left ventricle, but also to the right ventricle; as a result, the oxygenated blood supply will be insufficient. This results in necrosis. Veins and arteries are part of the circulation, and if any of them are blocked, the blood supply is restricted. Basically, the veins 'feed' blood to the left ventricle via the lungs. The amount of oxygenated blood supplied to the body is affected by the performance of the veins, because blood is 'recycled' (red blood cells have a life span of around 3-4 months, and it takes minutes for them to circulate). Cerebral venous infarction and cerebral arterial infarction are caused by numerous factors, and obviously result in blockage, or partial blockage of the arteries - which supply nutrients and blood to the brain - and/or the veins, which take away toxic waste products of cells' metabolism. Both involve the restriction of blood flow, which could be caused by atheroma deposition, vasoconstriction, aneurysms (and therefore blood leakage), blood viscosity etc. Blood clots/thrombi can form in the cerebral veins which lead down to the jugular; this causes venous infarction - the veins become congested and may eventually cause a cerebral haemorrhage. Again, the infarction is typically the result of the coagulating blood.