Chapter 5. The Childs Growth Friday, October 15, 2010 10:40 PM Cerebrum: the two connected hemispheres of the brain. Cerebral cortex: the covering layer of the cerebrum that contains the cells that control specific functions, such as seeing, hearing, moving, and thinking. Contains about 90% of the brains cell bodies. Neurons: a cell in the bodys nervous system, consisting of a cell body, a long projection called an axon, and several shorter projections called dendrites; neurons send and receive neural impulses, or messages, throughout the brain and nervous system. Neuron proliferation: the rapid proliferation of neurons in the developing organisms brain. 250,000 new neurons are born every minute. The brain gets bigger as we grow because existing neurons grow and the connections between them proliferate. Glial cells: a nerve cell that supports and protects neurons and serves to encase them in sheaths of myelin. This insulation makes the neuron more efficient in transmitting information. Myelination: the process by which glial cells encase neurons in sheaths of the fatty substance myelin. Neural migration: the movement of neurons within the brain that ensures that all brain areas have a sufficient number of neural connections. Synapse: a specialized site of intercellular communication where information is exchange between nerve cells, usually by means of a chemical neurotransmitter. Synaptogenesis: the forming of synapses. Begins early in prenatal life, as soon as neurons begin to evolve. Neuronal death (programmed cell death): the death of some neurons that surround newly formed synaptic connections among other neurons. Synaptic pruning: the brains disposal of the axon and dendrites of a neuron that is not often stimulated. Frees up space for new synaptic connections. Both of these functions are to increase the speed, efficiency, and complexity of transmissions between neurons and to allow room for new connections to develop as the child encounters new experiences. Hemispheres: the two, left and right, halves of the brains cerebrum. Corpus callosum: the band of nerve fibres that conne
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