Basic Review (Unique Brain and Histology) Flashcards
How is the brain unique in response to injury?
Glial cells form scars, not fibroblasts.
Does the brain have lymphoid drainage?
No, it has CSF system instead.
4 Types of Glial Cells
Astrocytes, oligodendrocytes, ependymal cells, microglia
Astrocytes
Make up 20-50% of brain volume. Provide structural framework for CNS, metabolic support, maintain ion balance, SUPPLIES GLUTAMATE TO NEURONS, ectodermal origin.
Oligodentrocytes
Myelinate neurons in the CNS, ectodermal in origin
Microglia
MESODERMAL in origin, resident macrophages, no known function in resting state but make cytokines and neurotoxins that mediate neuronal inflammation and kill damaged neurons
What parts of the CNS are most sensitive to anoxia?
Soma > axon > myelin > oligodentrocytes > astrocytes > microglia > blood vessels
Most sensitive brain regions to anoxia or glucose deprivation
Cortical layers 3 and 5, hippocampal neurons (CA1), purkinje cells
Eosinophilic degeneration
Cytoplasm becomes eosinophilic and nucleus becomes pyknotic after injury. Happens 4-6 hours after injury and is irreversible.
Axonal Reaction to injury
Reversible if the integrity of the exon is restored, but otherwise, the soma swells and rounds, nissl substance (RER) disappears, nucleus moves to the side.
3 Steps of Glial Scar formation
1) Astrocytes proliferate
2) Astrocytes become reactive (cytoplasm swells, processes extend)
3) Glial scar deposited made of Glial Fibrillary Acidic Protein (GFAP).
Vasogenic edema
Failure of BBB astrocytes and endothelial junctions. Allows normally intravascular fluid to penetrate into the cerebral parenchyma. Responsive to steroids and osmotic therapy and frequently seen with tumors/abscesses/trauma.
How to treat vasogenic edema?
Steroids and osmotic therapy (mannitol –diuretic)
Cytotoxic Edema
BBB intact, but hypoxia/ischemia/overdose damages endothelial cells and astrocytic processes. Causes failure of ion pumps, retention of sodium, water rushes in, cell swells. Does not respond to steroids/diuretics
How to treat cytotoxic edema?
Does not respond to steroids/osmotics.
Symptoms of increased intracranial pressure:
Headache, nausea, vomiting, bradycardia, LOC.
Monroe-Kellie Doctrine
Skull has a fixed volume that is normally filled by brain matter, CSF, and blood in the correct volumes. However, when the volume of one of these three things increases, the volume of the other two must decrease. If they don’t an increase in intracranial pressure will occur.
Cerebral Perfusion Pressure
MAP-ICP = CPP
Two places of neuronal generation?
Hippocampus and SVZ (lateral ventricles).
Ependymal Cells
Line ventricles
Multipolar Neuron
Many dendrites surround soma, long axon
Bipolar Neuron
Cell body integrated into middle of cell, dendrites and axon on either side of projection. CN VIII and retina.
Unipolar Neuron
Cell body is a separate process (looks like a bud). Sensory neurons.
Amacrine Cells
No axon at all, found in retina
Histologic characteristic of spinal cord motor neurons
Nissl Substance
Where are schwannomas common?
At the point of entry of CN VIII to brainstem
Important differences between the meninges of spinal cord and cerebrum
Cerebrum has 2 layers of dura and only 1 pial layer. Cerebral blood vessels lie on the surface of the intima pia (as opposed to epipia). Arachnoid villi are much more common in cerebellum.
Bones of the cranium
Frontal, parietal (2), temporal (2), occipital, sphenoid, ethmoid.
Three main compartments of base of skull
Anterior, Middle, posterior fossa.
CSF Cisterns
Quadrigeminal cistern, interpeduncular cistern, pontine cistern, cisterna magna, lumbar cistern.
