Lecture 4: Histology of CNS (Dennis) Flashcards
What substance causes neurons to appear opaque in a histological staining? What does it represent?
Nissl substance/bodies
Represents large, basophilic masses of free polysomes and Rough ER due to neurons being highly metabolic
What is the role of dendritic spines?
Known for their plasticity and ability to increase receptive area of the neurons
Increase in Surface Area
What are telodendria?
Dilation of branch ends of axons that contact postsynaptic cells
What is a neuropil?
The surrounding meshwork and structure that support the neuronal cell bodies
- Works with glial cells*
- Not part of cell body!*
What type of neuron is most common throughout the CNS? What do they function as?
Multipolar
Motor neurons, CNS interneurons
What is the most common function of bipolar neurons?
Sensory neurons of retina, olfactory mucosa, and inner ear
What type of neuron is found in dorsal root and cranial ganglia?
Unipolar/Pseudounipolar
What motor protein is utilized in anterograde transport?
Kinesin (uses ATP)
Cell body –> axon
What motor protein is utilized by retrograde transport?
Dynein
Axon –> Cell Body
What is the speed of slow transport?
What type of transport is this utilized by?
0.2-4 mm/day
Anterograde
Examples: Cytoskeletal Elements
What is the speed of fast transport?
What is conveyed in either direction?
20-400 mm/day
Anterograde: Membrane-limited organelles, sER components, synaptic vesicles, mitos
Retrograde: membrane-limited organelles, molecules endocytosed at axon terminal (toxins and viruses)
Most synapses in the body are ___ synapses.
Chemical
Utilizing NT
How does electrical current pass through neurons?
Gap junctions
Connexon proteins connect pre and post synaptic membranes
On a histological image, what would differentiate between a chemical and electrical synapse?
Chemical synapse has a vesicular presynaptic cell
Electrical synapse has visible connexon protiens
What is the function of glial cells?
Support cells involved in conduction speed, repair, neurotransmitter maintenance
What are types of glial cells found in the CNS?
- Astrocytes
- Oligodendrocytes
- Ependymal cells
- Microglia
What is the function of astrocytes?
- Prevent leakage into Blood Brain Barrier
- Moderate NT Intake
- Clear Debris
Astrocytes produce perivascular feet that perform what function?
Modulate blood flow and move nutrients and metabolites between neurons and capillaries
What protein reinforces the proximal regions of astrocytes?
Glial Fibrillary Acid Protein (GFAP)
Stains Green
What is the role of oligodendrocytes?
Myelinate axons from multiple neurons
Similar to Schwann Cells in PNS
What type of epithelium are ependymal cells?
Where are they found
Columnar or cuboidal cells lining ventricles of the brain and central canal of spinal cord
What is the role of ependymal cells?
Facilitale CSF movement
What is the choroid plexus composed of?
Thin layer of well-vascularized pia mater covered by cuboidal ependymal cells
Where is choroid plexus found?
Roofs of 3rd and 4th ventricles
Parts of lateral ventricular walls
What does the choroid plexus do?
- Removes water from blood and releases it as CSF
- Has tight junctions to prevent leakge of Blood-CSF barrier
What are fronds?
Branches of choroid plexus that is forms a villous structure
What neural cells act similar to phagocytes and are the major mechanism of immune defense in the CNS?
Microglia
In the spinal cord, where is gray and white matter located?
Gray Matter: Internal
White Matter: External
Sacral region has more gray matter than cervical
How can you tell the difference between anterior and posterior horn?
- Can look for motor cell bodies in anterior horn
- Most of the time, anterior horn is bigger
Where is the central canal located?
What is its significance?
- Central commissure of grey matter
- Lined by ependymal cells and has CSF
What are the three layers of cerebellar cortex?
- Molecular Layer: Lot of neuropil
- Purkinje Cells: Thin layer that extends dendrites through moleculre layer
- Granular Layer: Densly packed neurons
What are the cerebral cortical layers?
- Molecular Layer: Mostly neuroglial cells and horizontal cells of Cajal
- External Granular Layer: Small pyramidal cells and granule cells
- External Pyramidal Layer: Medium pyramidal cells
- Inner Granular Layer: Small granule cells
- Ganglionic Layer: Huge pyramidal cells (Betz)
- Multiform Layer: Fusiform Cells
What cortical layers contain the pyramidal cells?
Layer 2: Small pyramidal cells
Layer 3: Medium pyramidal cells
Layer 5: Large pyramidal cell layer - Betz Cells
What tissue is this?
What is the outer layer? What is the deep layer?
Cerebellar Cortex
A patient’s MRI shows thinning of cerebral gyri in the frontal and temporal lobes. What disease process is associated with this finding?
Alzheimer’s disease
What structures are found in a histological slide for a patient with this disease?
Amyloid B plaques
Neurofibrillary tangles: abnormal accumulation of tau
Where is dopamine found?
Neuromelanin pigments in substantia nigra
What are some features of Parkinson’s Disease on a histological slide?
- Lewy Bodies
- Pale halo
- Aggregates of α-synuclein
