Neuronal plasticity
Neuronal plasticity is an essential component of neuronal adaptability and there is increasing evidence that this is primarily a biochemical rather than a morphological process. The neuron is not a fixed entity in terms of the quantity of transmitter it releases, and transmitters which are co-localized in a nerve terminal may be differentially secreted under different conditions. This, together with the repeated firing of some neurons that appear to have ‘‘leaky’’ membranes, may underlie the rhythmicity of neuronal activity within the brain. Plasticity is also evident at the level of the neurotransmitter receptors. These are fluid structures that can be internalized into the membrane so that their density, and affinity for a transmitter, on the outer surface of the nervemembrane may change according to functional need. Perhaps it is not surprising to find that our knowledge of how the brain works and where defects that lead to abnormal behaviour can arise is so deficient. The approach to understanding the biochemical basis of psychiatric disease is largely based on the assumption that the brain is chemically homogeneous, which is improbable! Nevertheless, there has been some success in recent years in probing the changes that may becausally related to schizophrenia, depression and anxiety. It should be apparent to anyone interested in the neurosciences that the brain is more than a sophisticated computer that follows a complicated programme, and any dogmatic approach to unravelling the complexities of this dynamic, plastic collection of organs which we call ‘‘brain’’ is doomed to failure.
Neuronal plasticity is an essential component of neuronal adaptability and there is increasing evidence that this is primarily a biochemical rather than a morphological process. The neuron is not a fixed entity in terms of the quantity of transmitter it releases, and transmitters which are co-localized in a nerve terminal may be differentially secreted under different conditions. This, together with the repeated firing of some neurons that appear to have ‘‘leaky’’ membranes, may underlie the rhythmicity of neuronal activity within the brain. Plasticity is also evident at the level of the neurotransmitter receptors. These are fluid structures that can be internalized into the membrane so that their density, and affinity for a transmitter, on the outer surface of the nervemembrane may change according to functional need. Perhaps it is not surprising to find that our knowledge of how the brain works and where defects that lead to abnormal behaviour can arise is so deficient. The approach to understanding the biochemical basis of psychiatric disease is largely based on the assumption that the brain is chemically homogeneous, which is improbable! Nevertheless, there has been some success in recent years in probing the changes that may becausally related to schizophrenia, depression and anxiety. It should be apparent to anyone interested in the neurosciences that the brain is more than a sophisticated computer that follows a complicated programme, and any dogmatic approach to unravelling the complexities of this dynamic, plastic collection of organs which we call ‘‘brain’’ is doomed to failure.
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