Neuroscience: A Journey Through the Brain
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Synapse Formation and Modification
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Once the neuron reaches its target cell, synapses are formed. Not all synapses are necessary, and therefore some axon branches are pruned before maturation. The degeneration of inappropriate axon terminals is likely due to lack of trophic or support signals from the target, and serve as a safety mechanism for preventing incorrect neural connections. Sometimes whole neurons die during neural development, a process called apoptosis (naturally occurring cell death). Approximately 50% of of cells die at the time of synaptogenesis (synapse formation) in the target tissue. If the target is partially or totally ablated, neurons are lost proportionately to the amount of target removed. Adding additional target or providing trophic factors rescues cells that would otherwise have died.
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Last Updated: April 09, 2002 08:56 PM