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Abstract
Glucose is the primary source of energy for neurons. Metabolic pathways convert the glucose to adenosine triphosphate (ATP) which when broken down to adenosine diphosphate (ADP), provides energy for most cellular processes. Pumping ions across the cell membrane is the largest energy requirement in the brain. Neurons also require energy to maintain their structure and internal function.
When the blood and/or oxygen supply to the brain is interrupted the production of ATP is blocked and ATP concentrations in the neurons fall leading to neuronal injury. Necrosis and apoptosis are the two main pathways that lead to permanent neuronal damage.
The metabolic responses to head injury occur in an integrated manner in the body. The body’s metabolic response to the stress of head injury is divided into three phases:
1. The ebb phase occurs immediately after injury and is usually
characterized by shock, and the body responds to injury with the release of
stress hormones that cause mobilization of glucose from liver glycogen
leading to hyperglycemia.
2. The flow phase represents the time after stability is achieved and it is
characterized by increased metabolic rate, increase in total body nitrogen
excretion and incidence of gluconeogenesis.
3. The anabolic phase is characterized by gradual normalization of energy
requirements and net protein synthesis.