Chapter 2: Neurons and Glia
Chapter 2: Neurons and Glia
1. Introduction * Although there are many neurons in the human brain (about 100 billion), glia outnumbers neurons by tenfold.
1:10 ratio. * Neurons are the most important cells for the unique functions of the brain. * Neurons sense changes in the environment, communicate these changes to other neurons, and command the body’s responses to these situations. * Glia, or glial cells, are thought to contribute to brain function mainly by insulating, supporting, and neighboring neurons.
2. The Neuron Doctrine * Histology: the microscopic study of the structure of tissues. * Breakthrough in histology: introduction of stains that could selectively color some, but not all, parts of the cells in brain tissue. * Franz Nissl: showed that a class of basic dyes would stain the nuclei of all cells and also stain clumps of material surrounding the nuclei of neurons (Nissl Stain) * Useful for two reasons: Distinguishes neurons and glia from one another and enables histologists to study the arrangement, or cytoarchitecture, of neurons in different parts of the brain. * Camillo Golgi: Discovered that by soaking brain tissue in a silver chromate solution, now called the Golgi Stain, a small percentage of neurons became darkly colored in their entirety. * The Golgi stain shows that neurons have at least two distinguishable parts: a central region that contains the cell nucleus, and numerous thin tubes that radiate away from the central region.
* Swollen region containing the cell nucleus has several names: cell body, soma, and perikaryon. * The thin tubes that radiate away from the soma are called neuritis and are of two types: axons and dendrites. * Cell body usually gives rise to a single axon. Axons act like wires that carry the output of the neurons. Dendrites act as the antennae o the neuron to receive incoming signals or input. * Camillo Golgi versus Santiago Ramon y Cajal: Golgi
1. Introduction * Although there are many neurons in the human brain (about 100 billion), glia outnumbers neurons by tenfold.
1:10 ratio. * Neurons are the most important cells for the unique functions of the brain. * Neurons sense changes in the environment, communicate these changes to other neurons, and command the body’s responses to these situations. * Glia, or glial cells, are thought to contribute to brain function mainly by insulating, supporting, and neighboring neurons.
2. The Neuron Doctrine * Histology: the microscopic study of the structure of tissues. * Breakthrough in histology: introduction of stains that could selectively color some, but not all, parts of the cells in brain tissue. * Franz Nissl: showed that a class of basic dyes would stain the nuclei of all cells and also stain clumps of material surrounding the nuclei of neurons (Nissl Stain) * Useful for two reasons: Distinguishes neurons and glia from one another and enables histologists to study the arrangement, or cytoarchitecture, of neurons in different parts of the brain. * Camillo Golgi: Discovered that by soaking brain tissue in a silver chromate solution, now called the Golgi Stain, a small percentage of neurons became darkly colored in their entirety. * The Golgi stain shows that neurons have at least two distinguishable parts: a central region that contains the cell nucleus, and numerous thin tubes that radiate away from the central region.
* Swollen region containing the cell nucleus has several names: cell body, soma, and perikaryon. * The thin tubes that radiate away from the soma are called neuritis and are of two types: axons and dendrites. * Cell body usually gives rise to a single axon. Axons act like wires that carry the output of the neurons. Dendrites act as the antennae o the neuron to receive incoming signals or input. * Camillo Golgi versus Santiago Ramon y Cajal: Golgi