Supporting Cells

Unlike other organs that are "packaged" in connective tissue derived from mesoderm (the middle layer of embryonic tissue), the supporting cells of the nervous system are derived from the same embryonic tissue layer (ectoderm) that produces neurons.

Physiology Nervous System

■ Figure 7.3 The relationship between the CNS and PNS. Sensory and motor neurons of the peripheral nervous system carry information into and out of, respectively, the central nervous system (brain and spinal cord).

The Nervous System: Neurons and Synapses 155

There are two types of supporting cells in the peripheral nervous system:

There are four types of supporting cells, called neuroglial (or glial) cells, in the central nervous system (fig. 7.5):

oligodendrocytes, which form myelin sheaths around axons of the CNS;

microglia, which migrate through the CNS and phagocytose foreign and degenerated material;

Schwann cells, which form myelin sheaths around 1.

peripheral axons; and satellite cells, or ganglionic gliocytes, which support 2.

neuron cells bodies within the ganglia of the PNS.

Neuron Gliocyte

vllv f

■ Figure 7.4 Three different types of neurons. Pseudounipolar neurons, which are sensory, have one process that splits. Bipolar neurons, found in the retina and cochlea, have two processes. Multipolar neurons, which are motor and association neurons, have many dendrites and one axon.

Types Neuroglia

■ Figure 7.5 The different types of neuroglial cells. Myelin sheaths around axons are formed in the CNS by oligodendrocytes. Astrocytes have extensions that surround both blood capillaries and neurons. Microglia are phagocytic, and ependymal cells line the brain ventricles and central canal of the spinal cord.

Table 7 .3 Supporting Cells and Their Functions*

Cell Type

Location

Functions

Schwann cells

PNS

Surround axons of all peripheral nerve fibers, forming a neurilemmal sheath, or sheath of Schwann; wrap around many peripheral fibers to form myelin sheaths; also called neurolemmocytes

Satellite cells

PNS

Support functions of neurons within sensory and autonomic ganglia; also called ganglionic gliocytes

Oligodendrocytes

CNS

Form myelin sheaths around central axons, producing "white matter" of the CNS

Microglia

CNS

Phagocytose pathogens and cellular debris in the CNS

Astrocytes

CNS

Cover capillaries of the CNS and induce the blood-brain barrier; interact metabolically with neurons and modify the extracellular environment of neurons

Ependymal cells

CNS

Form the epithelial lining of brain cavities (ventricles) and the central canal of the spinal cord; cover tufts of capillaries

to form choroid plexuses—structures that produce cerebrospinal fluid

*Supporting cells in the CNS are known as neuroglia.

to form choroid plexuses—structures that produce cerebrospinal fluid

*Supporting cells in the CNS are known as neuroglia.

- Schwann cell

Axon

Axon

Neurilemma
Sheath of Schwann (Neurilemma)

Myelin sheath

Myelin Sheath Formation Peripheral Axon

■ Figure 7.6 The formation of a myelin sheath around a peripheral axon. The myelin sheath is formed by successive wrappings of the Schwann cell membranes, leaving most of the Schwann cell cytoplasm outside the myelin. The sheath of Schwann is thus external to the myelin sheath.

3. astrocytes, which help to regulate the external environment of neurons in the CNS; and

4. ependymal cells, which line the ventricles (cavities) of the brain and the central canal of the spinal cord.

A summary of the supporting cells is presented in table 7.3. Recent evidence suggests a more exciting role for the ependymal cells that line the ventricles of the brain, and also for the astrocytes immediately adjacent to this region—they can function as neural stem cells. That is, they can divide and their progeny can differentiate (specialize) along different lines, to become new neurons and neuroglial cells. Reptile and bird brains have been known to generate new neurons throughout life, but only recently has this ability been demonstrated in mammalian (including human) brains.

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Responses

  • Harry
    What are the two types of support cells found in the pns?
    5 years ago
  • eric
    Where is the neuroglial cells in a neuron?
    5 years ago
  • SEMHAR SAARE
    What are the two processes found on a neuron?
    5 years ago
  • Lucius
    What are the supporting cells in the central nervous system called?
    5 years ago
  • Elvira Angelo
    Which supporting cell (neuroglia) forms a myelin sheath in the central nervous system?
    5 years ago
  • Eero
    Does microglia line the central canal of the spinal cord?
    5 years ago
  • Bruno
    What type of neuroglial cells provide support and nutrition to sensory ganglia in the pns?
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  • piia
    How many types of supporting cells are in the nervous system?
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  • kerstin
    What are two types of neuroglia in the pns?
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  • Kerstin
    What are the four types of supporting cells in the nervous system and their respective functions?
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  • Leonida
    Are supporting cells known as glial cells?
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  • julia
    What are the difference types of neuroglial cells?
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  • kathleen
    What supporting cells of the pns produce the myelin sheath for axons of neurons in the pns?
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  • hal
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  • ANJA
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  • alice
    Which neuroglial cell forms myelin sheath in axons in pns?
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  • Wanda
    What are three functions of supporting cells or neuroglia?
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  • MARIA
    What is the link between ventricles and supporting cells?
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  • cara
    Which type of neuroglia lines the ventricles of the brain?
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  • mezan
    What are the neuroglia that wrap around capillaries helping to form the bloodbrain barrier are:?
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  • Ulla-Maj
    What type of neuroglia line the ventricles of the brain?
    5 years ago
  • fulvus
    What are the neuroglial cells that form a myelin sheath around axons?
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  • stacy
    Which of the neuroglial cell types form myelin sheaths within the CNS?
    5 years ago
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    Which type of neuroglial cells is found supporting neuronal cell bodies within ganglia?
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  • quinto
    Which supporting cell is responsible for the myelin sheath in the cns?
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  • Monika
    What neurogilial cell type forms myelin sheath?
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  • mezan
    What type of neurologlical cells provide support and nutrition to sensory ganglia in the pns?
    4 years ago
  • mark
    What type of neuroglia cells suppport and privde nutrion?
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  • Elide Mazzanti
    Which of the neuroglial cell types shown form myelin sheaths within the CNS?
    4 years ago
  • ariam
    What different types of cells are found witihn the cns and pns?
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  • gorbulas
    Which type of neuroglia cell is found supporting neuronal cell bodies within neuroglia?
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  • jannette
    What cells form myelin in the central nervous system?
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  • j
    What are the 3 different variations of schwann cell?
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  • rikki
    Which supporting cells of the cns disposes of foreign material?
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    WHAT ARE THE FUNCTION OF SUPPORTING CELL?
    12 months ago
  • TUOMAS
    What are supportive cell where they found?
    11 months ago
  • Fabio
    What are the four neuroglia cells and their funtion?
    8 months ago
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  • matilda
    What are the support cells of the nervous system called?
    7 months ago
  • porro
    Are satellite cells support cells in the hippocampus?
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  • Fosco
    Which supporting cell can differentiate into another type of supporting cell in nervous system?
    5 months ago
  • donald
    What is are the supporting cell nerves and their function?
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  • wolfgang
    What is a CSf which type of cells humanbody have?
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    What are the two supporting cells of bone tissue?
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    What are 4 types of supporting cells found in the CNS?
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