Correct answer:

If the circulation is temporarily stopped at normal body temperature, organs suffer ischaemic damage owing to lack of oxygen, the extent varying according to the metabolic demand of the organ. The brain is the most sensitive tissue in this respect and is liable to irreversible changes after 3 minutes of ischaemia. The spinal cord is next, followed by heart muscle, which will tolerate between 3 and 6 minutes of ischaemia at normal temperature.