10 Questions
What is characteristic of astrocytes observed under electron microscopy?
Few organelles and lots of glycogen
What is the main role of oligodendrocytes?
To produce the myelin sheath
What is a function of astrocytes in the metabolism of neurotransmitters?
To recycle neurotransmitters
What is the role of astrocytes in energy metabolism?
To provide glucose to neurons
What is the function of astrocytes during brain damage?
To proliferate and secrete growth factors
What is characteristic of oligodendrocytes under light microscopy?
They are smaller than astrocytes
What is a characteristic of oligodendrocytes under electron microscopy?
A large nucleus and many cytoplasmic extensions
What is the main function of oligodendrocytes in relation to axons?
To produce the myelin sheath around axons
What is a characteristic of astrocytes in relation to the blood-brain barrier?
They form the blood-brain barrier
What is the difference between perineuronal and interfascicular oligodendrocytes?
Their location in the brain
Study Notes
Nerve Conduction
- Conduction speed varies: 3 to 14m/s (myelinated) and 0.5 to 2m/s (unmyelinated C fibres or Remak fibres)
- C fibres are found in the autonomic nervous system
Neuroglial Tissue
- Makes up half of the brain's mass
- Ensures:
- Support for the nervous system
- Nutrition for nerve cells
- Isolation of nerve elements from surrounding tissue
- Can proliferate to fill gaps left by destroyed neurons, potentially giving rise to tumors
Glial Cell Categories
- Central neuroglia:
- Epithelial/cerebral neuroglia: ependymocytes lining internal cavities and membranes
- Interstitial neuroglia: astrocytes, oligodendrocytes, and microcytes
- Peripheral/sheathing neuroglia:
- Schwann cells in peripheral nerves
- Satellite cells of nerve ganglia
- Terminal neuroglia/teloglia:
- Found in vegetative nervous system, organs of sensitivity, and motor plates
Astrocytes
- Star-shaped cells identified by silver salt staining
- Types:
- Fibrillar astrocytes: found in white matter with long cytoplasmic extensions
- Protoplasmic astrocytes: found in grey matter with short cytoplasmic extensions
Microglia Cells
- Phagocytosis and antigen presentation
- Secrete cytokines (IL-1, IL-6) influencing blood-brain barrier permeability and astrocyte stimulation
Ependymocytes and Choroid Plexuses
- Ependymocytes:
- Form simple ciliated epithelium lining ventricular cavities
- Allow CSF-nervous tissue exchanges, forming the CSF-brain barrier
- Choroid plexus:
- Evagination of ependymal epithelium into ventricular lumen
- Produces CSF (500 cc/day) and maintains its chemical stability and physiological quality
- Forms the blood-CSF barrier
Oligodendrocytes
- Description:
- Smaller than astrocytes
- Two types: perineuronal and interfascicular oligodendrocytes
- Electron microscopy:
- Nucleus with ribosomes, mitochondria, endoplasmic reticulum, and Golgi
- Cytoplasmic extensions surrounding axons, forming the myelin sheath
- Role:
- Produce the myelin sheath for multiple axons
Test your knowledge of the nervous system, including conduction speed, types of nerve fibers, and the role of glial cells.
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