The brain serves as the control center for the body. In order to function effectively, the brain needs a steady supply of oxygenated blood. Although the brain only makes up 2 percent of a human body's total weight, it receives 15 to 20 percent of the blood supply, according to Neuroscience For Kids. A decrease in the level of oxygen leads to a variety of effects on the brain, including hypoxia, anoxia and stroke.
Hypoxia
Hypoxia describes a condition characterized by a low level of oxygen in the brain. Hypoxia usually occurs even when the amount of blood flowing to the brain remains the same. Common causes of hypoxia include drowning, smoke inhalation, carbon monoxide poisoning, strangling, choking or head trauma, as described by the National Institute of Neurological Disorders and Stroke. Patients suffering from a heart attack, a condition in which the heart fails to receive enough oxygenated blood, may also experience hypoxia.
The symptoms of hypoxia depend upon the extent of the oxygen deprivation. Mild hypoxia causes an inability to pay attention, poor judgment, memory loss and a decrease in muscle coordination. The longer the brain experiences a lack of oxygen, the more intense these symptoms become. As the level of oxygen drops, the condition worsens from hypoxia to anoxia.
Anoxia
Anoxia involves the complete deprivation of oxygen in the brain tissue. Like hypoxia, the condition usually occurs even when the brain receives an adequate blood supply. The same conditions that cause hypoxia can lead to anoxia. Because brain cells fail to receive any oxygen, anoxia can lead to brain damage. The cells in the brain begin to die after only five minutes without oxygen, according to the National Institute of Neurological Disorders and Stroke. Anoxia may lead to a state of unconsciousness that may last from days to weeks or even months, depending on the length of time the brain experienced oxygen deprivation, according to the Centre for Neuro Skills.
Stroke
The National Stroke Association reports a stroke, also known as a brain attack, as the third leading cause of death in America. A stroke occurs when the blood flow, and therefore the oxygen flow, to the brain becomes inhibited. A blocked blood vessel leading to the brain can cause a stroke. A stroke can also occur when a blood vessel in the brain bursts, allowing blood to leak into the spaces surrounding the brain cells, depriving the cells of blood and oxygen.
Without blood and oxygen, the brain cells begin to die. The death of brain cells causes brain damage and results in symptoms including sudden numbness and weakness often felt on only one side of the body, confusion, difficulty walking, dizziness and a loss of balance. Depending on the area of brain affected, patients may also experience vision impairment or speech difficulties.
References
- Neuroscience For Kids: The Blood Supply of the Brain
- National Institute of Neurological Disorders and Stroke: NINDS Cerebral Hypoxia Information Page
- Centre for Neuro Skills: Anoxia/Hypoxia
- National Stroke Association: What is Stroke?
- National Institute of Neurological Disorders and Stroke: NINDS Stroke Information Page
