Histology: Central Nervous System Flashcards
What are the cells of neuroectodermal origin?
- Neurons
- Glial Cells
Cells of neuroectodermal origin include neurons and glial cells (astrocytes, oligodendrocytes, ependymocytes).
What are the cells of mesenchymal origin?
- Microglia/macrophages
- Meninges
- Choroid plexus
Cells of mesenchymal origin include microglia/macrophages, cells of the meninges, and cells of the choroid plexus.
What is found in the cerebral cortex gray matter?
Cell bodies, synapses and dendrites
What is found in the cerebral cortex white matter?
Myelinated axons
Gray matter covers the white matter in the ___________
Cerebral Cortex - this is opposite in the spinal cord.
What does Nissl stain stain?
Rough endoplasmic reticulum
What are the characteristics of motor neurons (size, axon length, etc)?
– Large cell body
– Have long axons
– Nucleus with single large nucleolus
– Prominent Nissl substance
What are the characteristics of interneurons (local circuit)?
– Small compact cell body
– Lack Nissl substance
– Short dendrites and small axons
What is the role of the principal neurons?
They have long axons and transmit information over long distances - an example are the motor neurons
What is central chromatolysis?
In response to destruction of axons - neuronal cell body balloons and nucleus is displaced to the periphery with the dispersion of the ribonucleoprotein
Neurophagia
Damage to the cell body directly may lead to it beyond surrounded by microglial cells - commonly seen in viral infections
Acute Neuronal Injury
Irreversible injury with cell body shrinkage and increased cytoplasmic eosinophilia and loss of nuclear chromatin
Where is the nucleus seen in a ballooned neuron?
Still remains central
Negri Body Association
Rabies
Lewy Body Association
Parkinson’s Disease
Hirano Body Association
Alzheimer’s Disease but also noted in normal individuals with aging
Function of Astrocytes
Aid with structure and repair of damaged neurons
What are the main types of astrocytes?
- Fibrillary
- Protoplasmic
Fibrillary Astrocytes
White matter – majority with
numerous and extensive processes
Protoplasmic Astrocytes
Gray matter – fewer branches
Gliosis
A non specific nervous system reaction to injury and involves hypertrophy of astrocytes
Function of Oligodendrocytes
Maintenance of function of myelin sheaths
Are there glia in the peripheral nervous system?
NO. Schwann cells will perform the functions of the oligodendrocytes.
What happens with loss of oligodendrocytes?
Leads to demyelination
Microglia
Not “true” glia - they are monocytes that are CD68+ and act as phagocytic and Ag-presenting cells
Where are microglia found?
Found evenly in the gray and white matter
Ependyma
Specialized glia that line the ventricles and have cilia - no basement membrane is present though
What is the function of ependyma?
Mainly as barrier between the brain and CSF
Choroid Plexus
Made of folds of CSF secreting ependymal cells that protrude into the ventricles
Pia Mater
Thin layer over the brain and the spinal cord
