BIOL 3402 Lecture Notes - Lecture 11: Nerve Growth Factor, Schwann Cell, Axon
Document Summary
About 1 trillion neurons in nervous system. Neuroglia outnumber neurons by 10 to 1. Bind neurons together and for framework for nervous tissue. In fetus, guide migrating neurons to their destination. Mature neuron is covered by glial cells: prevents neurons from touching eachother, gives precision to conduction pathways. Ependymal: line internal cavities of brain; make cerebrospinal fluid. Microglia: wander through cns looking for debris and damage. Develop from white blood cells and become concentrated at damaged areas. Astrocytes: most abundant, covering brain surface in gray matter. Extensions that contact capillaries and form blood-brain barrier. Regulate chemical composition of tissue fluid by absorbing excess neurotransmitters and ions. Astrocytosis (sclerosis) = when neuron is damaged, astrocytes form hardened scar tissue to fill in space. Schwann cells: envelope nerve fibers in pns, wind around nerve fiver, produce myelin sheath similar to what oligodendrocytes make, assist in regeneration of damaged fibers.
