Final answer:
Permanent brain damage can occur if the brain is without oxygen for more than a few minutes. Brain cells require a constant supply of oxygen to function properly and can begin to deteriorate within minutes without oxygen. Survival without lasting effects is possible in exceptional circumstances, such as cold water rescues.
Step-by-step explanation:
Permanent brain damage can occur if the brain is without oxygen for more than a few minutes. Brain cells are highly sensitive to lack of oxygen, as they require a steady production of ATP to function properly. Within five minutes without oxygen, brain damage is likely, and death is likely within ten minutes.
When the brain is deprived of oxygen for too long, it can result in a stroke or cerebrovascular accident (CVA), which causes the death of brain cells. Neurons, the building blocks of the brain, begin to deteriorate within one or two minutes without oxygen, and permanent cell death can occur within a few hours.
It's important to note that the brain can be resilient in certain circumstances. One example is when a person is rescued from cold water and quickly receives CPR. In such cases, there have been instances where individuals have survived without lasting ill effects for up to an hour without oxygen.