PSYC 401 Chapter Notes - Chapter 4: Sympathetic Nervous System, Cerebral Cortex, Synaptogenesis
Document Summary
In vertebrate embryos, the central nervous system begins as a tube surrounding a fluid-filled cavity. Developing neurons proliferate, migrate, differentiate, myelinate, and generate synapses. Neuron proliferation varies among species mainly by the number of cell divisions. Migration depends on a large number of chemicals that guide immature neurons to their destinations. In adult vertebrates, new neurons can form in the olfactory system, the hippocampus, and the song-producing brain areas of some bird species. Adult humans form new neurons in the hippocampus but few or none in the olfactory bulbs or cerebral cortex. Growing axons find their way close to the right locations by following chemicals. Then they array themselves over a target area by following chemical gradients. After axons reach their targets based on chemical gradients, the postsynaptic cell adjusts the connections based on experience, accepting certain combinations of axons and rejecting others competition among axons continues throughout life. Nervous system develops far more neurons than will actually survive.
