Glial Cells
GLIAL CELLS
Summary
Overview
Glial cells vs neurons
- Glial cells are smaller than neurons and are closely associate with neurons.
Gray matter
- Comprises neurons' dendrites and cell bodies
White matter
- Comprises the neurons' axons
6 TYPES OF GLIAL CELLS
Central Nervous System
1) Astrocytes (Macroglia)
- Star-shaped
- Support and brace neurons
- Anchor neurons to supply lines
- Help determine capillary permeability (helping to form blood/brain barrier)
- Guide young neuron migration and synapse formation
- "Mop up" extracellular potassium and neurotransmitters
- Two Key Subcategories of Astrocytes:
- a) Protoplasmic astrocytes: thick, branched processes that attach to neurons and vessels.
- b) Fibrous astrocyte: long, thin, unbranched processes; found in white matter.
Clinical correlation: Astrocytoma
2) Microglial cells
- Thorny processes monitor neuronal health
- Can morph into special type of macrophage to phagocytose pathogens or dead neurons
3) Ependymal cells
- Form a somewhat permeable barrier between cerebrospinal fluid filled cavities and the tissue of the brain or spinal cord (not to be confused with blood/brain barrier)
- Cilia can help circulate the cerebrospinal fluid
Clinical correlation: Ependymoma
4) Oligodendrocytes (Macroglia)
- Similar shape to astrocytes
- Create myelin sheath within central nervous system
- A single oligodendrocyte can create multiple myelin segments
Clinical Correlation: Oligodendroglioma, Multiple sclerosis
B) Peripheral Nervous System
5) Satellite cells
- Small cells surrounding neuronal cell bodies in the peripheral nervous system
- Thought to have many of the same support functions as astrocytes
6) Schwann cells (neurolemmocytes)
- Create myelin sheath in the peripheral nervous system
- Each Schwann cell creates single myelin segment, so there is a bulge in each segment where the nucleus and most of the cytoplasm is located
Clinical Correlation: Guillain-Barre Syndrome