Understanding neuroanatomy, histology, and physiology are integral for medical students who are laying the foundation of neurology. For residents and fellows, reviewing such material serves as a refresher of topics not regularly confronted in clinical practice but are often seen on in-service and board examinations. In this section, we will cover CNS histology, anatomy as well as briefly mention some associated neurological syndromes.
Authors: James Eaton MD, Brian Hanrahan MD
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Table of Contents
Central Nervous System Histology
- Provide support and protection for neurons.
- Glial cells outnumber neurons 10 to 1 in the central nervous system.
- The largest glial cell.
- Support function of neurons in multiple ways:
- Regulates interstitial fluid.
- Modulates signals that regulate blood flow in response to neuronal activity.
- Provides structural and nutritional support.
- Remove excess glutamate from synapses.
- Produce numerous angiogenic factors including VEGF.
- VEGF decreases the stability of the blood-brain barrier with inflammatory conditions and CNS tumors.
- Immunohistochemical staining for glial fibrillary acidic protein (GFAP) can be used to identify astrocytes.
- Glial fibrillary acid proteins (GFAP) make up intracellular intermediate filaments located in astrocytic processes.
Microscopic images of astrocytes
- Responsible for the formation of myelin in the central nervous system which provides electrical insulation.
- Oligodendrocytes have condensed, rounded nuclei and unstained cytoplasm.
- Myelinated fibers can be easily identified on microscopic slides with Luxol fast blue (LFB) staining.
- The lack or paucity of LFB staining can suggest demyelinating disease.
- Leukodystrophies typically involve metabolic and lysosomal pathways that are necessary for normal oligodendrocyte function.
- Progressive Multifocal Leukoencephalopathy (PML) likely involves lytic infection of oligodendrocytes to induce demyelination.
- Oligodendrogliomas are primary brain tumors with a classic ‘chicken wire’ appearance on histopathology.
Oligodendrocytes vs. Oligodendroglioma
- Produces and facilitates the movement of cerebrospinal fluid (CSF).
- Lines the ventricles and central canal of the spinal cord.
- Resembles simple columnar epithelium with some cilia on histopathology.
- The primary immune cell of the central nervous system.
- The smallest and rarest glial cell.
- Derived from bone marrow/monocytes and enter the CNS in the perinatal period.
- All other glial cells and neuronal cells are derived from neural tube cells.
- Responsible for receiving, integrating, and propagating information to other cells.
- Contains three parts; dendrites, cell body, and axon(s).
- Receive information from other neurons at synapses.
- Changes in dendritic spines are critical for neural plasticity that occurs during development and learning.
- Cell body
- The main synthetic and trophic center of the cell which contains the nucleus and most organelles.
- Easily identified by a large central and euchromatic nucleus with a prominent nucleolus.
- Basophilic clumps of polyribosomes are called Nissl bodies.
- Conducts information to muscles, glands, or neurons.
- Axons terminate at synapses.
Illustration and pathology slide of neuronal slides
- Most neurons contain multiple dendrites and only one axon.
- Neurons can be easily identified with silver staining on microscopic slides which impregnate neurofilaments.
- Intracellular neurofibrillary tangles can suggest a neurodegenerative disease such as Alzheimer’s.