MODULE SUPPLEMENT: NEUROLOGICAL SYSTEM
The Neuron

The functional unit of the nervous system is the neuron, which includes the cell body along with its dendrites and an axon. Also of central importance to the functioning of the nervous system are synapses and their synaptic connections because this is where communication transfer actually occurs. Changes in the synapse, neurotransmitter release or elimination, or changes in receptors on the post synaptic as well as pre-synaptic membranes can have a major impact on neurologic function.

Changes that occur with age often affect the cytoskeleton, which is the intra-cellular structural component of the neuron that include filaments and microtubules. These intra-cellular components are critical to normal neuronal function and nourishment. Cytoskeletal proteins are found to undergo modification in certain areas of the brain with age, but are especially affected in certain disease states such as Alzheimer's Disease and Parkinson's Disease (Mattson, 1999). The cause of these changes, especially in the latter disease states, has been attributed to increased intracellular calcium and oxidative stress (e.g. free radical damage accumulation) (Mattson, 1999). This relates back to the discussion of free radicals and the idea that, per the disposable soma theory, we can't afford to expend the energy that would be required to correct all the damage that accumulates. 

Also see: Module Two: Biology and Physiology of Aging.
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