Human brain biochemistry

The human brain that serves as a centre of the nervous system is structurally unique. It is extraordinarily complex and highly specialized in its distinct heterogeneous anatomical regions as its function remains a great challenge. The neuron is the functional unit that depends on special anatomical and chemical connections with other units of the system. The essential biochemical connections of the nerve cell have special morphological features: synaptic contact that is mediated by chemical molecules ensures sequential propagation of neurotransmission of electrical pulses through units of the system. The chemical energy expended in maintaining the distribution gradients of cations across cellular membranes, and the chemical neurotransmission causes an alteration in cation distribution. The energy utilization mechanisms that underlie cations re-distribution are not peculiar to the nervous system, but they are of particular importance to neural function because the mechanisms of chemical transmission are peculiar to the nervous system. Nerve cells have the ability to trigger off and maintain conduction of electrical impulses over long distances in meters, without a significant loss of impulse strength. Such unique features are based on semi-permeable excitable membranes that alter permeation to small chemical molecules and to cations. The biochemical function of the brain is demonstrated in the efficient production of energy required to accomplish the processes mentioned above, and it is essentially ATP that is stored and produced from glucose oxidation to carbon dioxide and water. The brain has virtually no reserves of chemical energy (glucose 1-2 µmoles/g and ATP 3 µmoles/g) to function for minutes only, considering that this organ is 2% of total adult weight that consumes 20% of the whole body glucose through a constant blood supply. Yet, the various factors that regulate glucose uptake and its utilization in the central nervous system are not well understood. This review is an attempt to update the rapidly expanding information on human brain neurotransmission biochemistry, though the adaptive processes of learning; cognitive performance and memory in the brain have subtle relationships.