glial cell

Examples of glial cell in the following topics:

• Introducing the Neuron

  • Neurons are specialized cells that transmit chemical and electrical signals.
  • The brain is made up entirely of neurons and glial cells, which are non-neuronal cells that provide structure and support for the neurons.
  • The cell body contains a specialized structure, the axon hillock, which serves as a junction between the cell body and the axon.
  • Myelin is produced by glial cells (or simply glia, or "glue" in Greek), which are non-neuronal cells that provide support for the nervous system.
  • In the central nervous system, the glial cells that form the myelin sheath are called oligodendrocytes; in the peripheral nervous system, they are called Schwann cells.

• Cerebral Cortex

  • It contains glial cells, which guide neural connections, provide nutrients and myelin to neurons, and absorb extra ions and neurotransmitters.
  • Gray matter is the mass of all the cell bodies, dendrites, and synapses of neurons interlaced with one another, while white matter consists of the long, myelin-coated axons of those neurons connecting masses of gray matter to each other.

• Neurotransmitters

  • Neurotransmitters are chemicals that transmit signals from a neuron across a synapse to a target cell.
  • Neurotransmitters are chemicals that transmit signals from a neuron to a target cell across a synapse.
  • A neuron has a negative charge inside the cell membrane relative to the outside of the cell membrane; when stimulation occurs and the neuron reaches the threshold of excitement this polarity is reversed.
  • When the chemical message reaches the axon terminal, channels in the postsynaptic cell membrane open up to receive neurotransmitters from vesicles in the presynaptic cell.
  • A pump in the cell membrane of the presynaptic element, or sometimes a neighboring glial cell, clears the amino acid from the synaptic cleft so that it can be recycled, repackaged in vesicles, and released again.

• Cognitive Development in Childhood

  • Once nerve cells in the brain are in place, they form synapses.
  • Glial cells, which account for half of all brain mass in early childhood, are responsible for a process known as myelination.
  • Synapses, or the spaces between nerve cells, develop rapidly during childhood.

• Mechanics of the Action Potential

  • It is not a physical component of a cell but rather a name for the gap between two cells: the presynaptic cell (giving the signal) and the postsynaptic cell (receiving the signal).
  • During a chemical reaction, a chemical called a neurotransmitter is released from one cell into another in an electrical reaction, the electrical charge of one cell is influenced by the charge an adjacent cell.
  • Presynaptic cell: a specialized area within the axon of the giving cell that transmits information to the dendrite of the receiving cell.
  • Postsynaptic cell: a specialized area within the dendrite of the receiving cell that contains receptors designed to process neurotransmitters.
  • During the refractory phase this particular area of the nerve cell membrane cannot be depolarized; the cell cannot be excited.

• Gustation: Taste Buds and Taste

  • Each taste bud is flask-like in shape and formed by two types of cells: supporting cells and gustatory cells.
  • Gustatory cells are short-lived and are continuously regenerating.
  • An ion channel in the taste cell wall allows Na+ ions to enter the cell.
  • This depolarizes the cell and floods it with ions, leading to a neurotransmitter release.
  • The third allows sodium ions to flow down the concentration gradient into the cell.

• The Role of Genes in Prenatal Development

  • Every person is made up of cells, each of which contains chromosomes.
  • Gene regulation is the process by which cells differentiate.
  • Among other things, it is the process in which a cell determines which genes it will express and when.
  • Cell differentiation is a process by which a less specialized cell becomes a more specialized cell.
  • For example, as a zygote develops, gene regulation changes some cells into brain cells and others into liver cells.

• Prenatal Brain Development

  • A zygote begins as a one-cell structure that is created when a sperm and egg merge.
  • During the first week after conception, the zygote rapidly divides and multiplies, going from a one-cell structure to two cells, then four cells, then eight cells, and so on.
  • This process of cell division is called mitosis.
  • After 5 days of mitosis there are 100 cells, and after 9 months there are billions of cells.
  • As the cells divide, they become more specialized, forming different organs and body parts.

• Stages of the Action Potential

  • Neural impulses occur when a stimulus depolarizes a cell membrane, prompting an action potential which sends an "all or nothing" signal.
  • The sensory input stage is when the neurons (or excitable nerve cells) of the sensory organs are excited electrically.
  • Depolarization, also referred to as the "upswing," is caused when positively charged sodium ions rush into a nerve cell.
  • During the refractory phase this particular area of the nerve cell membrane cannot be depolarized.
  • Damage to the myelin sheath from disease can cause severe impairment of nerve-cell function.

• Neural Networks

  • If a stimulus creates a strong enough input signal in a nerve cell, the neuron sends an action potential and transmits this signal along its axon.
  • The axon of a nerve cell is responsible for transmitting information over a relatively long distance, and so most neural pathways are made up of axons.
  • The basic neuronal function of sending signals to other cells includes the capability for neurons to exchange signals with each other.
  • In 1949, neuroscientist Donald Hebb proposed that simultaneous activation of cells leads to pronounced increase in synaptic strength between those cells, a theory that is widely accepted today.
  • Cell assembly, or Hebbian theory, asserts that "cells that fire together wire together," meaning neural networks can be created through associative experience and learning.