Neuroglia of the CNS
Astrocytes functions: Creating 3 dimensional framework for CNS
Astrocytes are packed with microfilaments that extend across the breadth of the cell=mechanical strength and astrocytes form structural framework supporting neurons of brain and spinal cord.
name four types of neuroglia
Astrocytes, oligodendrocytes, microglia and ependymal cells.
Oligodendrocytes function
Myelinates CNS axons; provides structural framework
What is grey matter?
Regions dominated by neuron cell bodies, dendrites and unmyelinated axons. =dark grey dusky color
Summary of function of Microglia
Remove cell debris, wastes and pathogens by phagocytosis.
Astrocytes functions: Guiding neuron development
in embryonic brain, astrocytes are involved in directing growth and interconnection of developing neurons via secretion of chemicals called neurotropic factors.
Oligodendrocytes: myelin sheath gaps
small gaps (nodes of ranvier) exist between myelin sheath produced by adjacent oligodendrocytes
Microglia composition
smallest of glial cells slender cytoplasmic processes with many fine branches (microglia cells)
Oligodendrocytes processes
usually contact axons and cell bodies of neurons. tie axons together improve functional performance of neurons by wrapping axon in myelin (material with insulating properties)
Ependymal cells: where are they found?
Ventricles of the brain and central canal of spinal cord. (ependyma)
Function of Microglia
act as roving security system. phagocytic cells of CNS. Engulf cellular debris and waste products. Protect CNS by phagocytosing viruses, microorganisms and tumor cells. in times of infection or injury % increases.
Microglia lowdown
appear in embryonic development through division of mesodermal stem cells. these stem cells also related to produce tissue macrophages and monocytes of blood. migrate to CNS =remain in neural tissue.
Astrocytes functions: Performing repairs in damaged neural tissue
astrocytes make structural repairs that stabilize tissue and prevent further injury via scar tissue.
Ependymal cells composition with CSF
chamber and passageways filled with cerebral spinal fluid (CSF). fluid provides protective cushion, and transports dissolved gases, nutrients, wastes and other materials. Cuboidal, slender processes branch extensively and make direct contact with glial cells in surrounding neural tissue. free surfaces covered in cilia (may assist in circulation of CSF)
Astrocytes (largest amount of glial cells)
controlling interstitial environment, maintaining the blood brain barrier, creating three dimensional framework for CNS, performing repairs in damaged neural tissues and guides neuron development.
Astrocytes functions: Controlling interstitial environment
large amounts of cytoplasmic processes which increase surface area, which facilitate scavenging of ions, neurotransmitters or metabolic by-products. Exchange of ions and etc. with extracellular fluid enables astrocytes to control chemical content of interstitial environment of CNS.
Ependymal cells function
line ventricle (brain and central canal); assist in producing, circulating and monitoring cerebrospinal fluid
Astrocytes functions: Maintaining blood brain barrier
neural tissue is physically and biochemically isolated from general circulation. hormones or other chemicals in blood can disrupt neuron function. Endothelial cells lining CNS capillaries are responsible for blood brain barrier. Control chemical exchange between blood and interstitial fluid. Cytoplasmic blanket only interfered when other glial cells contact capillary walls.
what is white matter?
regions dominated by myelinated axons of CNS =appear glossy white
Oligodendrocytes: Internodes
relatively large areas wrapped in myelin sheath
Oligodendrocytes composition
resemble astrocytes only in that they both have smaller cell bodies and fewer shorter cytoplasmic processes.