Hypoxia is a deficiency of oxygen to tissues in the body, particularly the brain. Brain cells begin to die after five minutes without oxygen, so severe brain damage or death can occur quite rapidly after the onset of hypoxia.
Dopamine is a neurotransmitter that controls movement, emotional responses and the ability to experience pleasure or pain. A drop in dopamine can cause muscle stiffness, decreased mobility, depression and eventually Parkinson's disease, while increased levels can cause mental deterioration, dementia, hallucinations and schizophrenia. A decrease in oxygen in the body slows the dopamine receptors, preventing them from functioning normally.
Causes of Hypoxia
Hypoxia is nearly always unexpected and, therefore, cannot be prevented. Common causes include factors with the lungs (smoke inhalation, carbon monoxide poisoning, drowning and problems with anaesthesia), the rest of the body (choking, paralysis, low blood pressure, strangulation and heart attack), and external agents (drug overdose and high altitudes).
Symptom of Hypoxia
People suffering from mild hypoxia generally become uncoordinated, inattentive and lack proper judgment, while severe hypoxia leaves a person in a coma, unable to breathe and unresponsive to light. If the heart is the only organ still responding, people are declared brain-dead.
When the brain is not receiving enough oxygen, cells throughout the body send signals to the brain, through dopamine, to increase breathing. As the oxygen levels decrease, the levels of dopamine outside the cells increase and cause damage to the brain, but scientists are still uncertain as to the exact reasons these injuries occur.
During heart failure, the heart beats irregularly, restricting the flow of blood through the body and reducing the amount of oxygen that reaches vital tissues. Dopamine triggers the heart to increase the strength of the contractions, causing it to pump more blood and re-oxygenate the tissue. Infants who undergo heart surgery often develop a heart condition caused by a lack of oxygen to the heart (cyanotic congenital heart disease) where hypoxic blood is always present in the heart.
Chronic hypoxia is when the body experiences low oxygen levels for an extended period of time. Dopamine receptors elevate for the first two days, then drop to more normal level for the following week, then rise again. People suffering from extreme chronic hypoxia typically need lifelong medical assistance because their bodies are no longer able to regulate dopamine production, but people with mild chronic hypoxia, such as those living at high altitudes, are able to live normal lives.
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- University of Maryland Medical Center: Cerebral Hypoxia-Overview
- Brain Research-Molecular Brain Research: Time-Dependent Changes in Dopamine D(2)-Receptor mRNA in the Arterial Chemoreflex Pathway with Chronic Hypoxia
- Stanford.edu: The Hypoxic Response: Huffing and HIFing
- Uky.edu: The Pharmacology of Adrenergic Receptors: Sympathomimetics Acting at Beta Receptor Systems