CNS Histology Flashcards
Dense network of interwoven nerve fibers and their branches+synapses, together with glial filaments
Neuropil
Describe cell body of large typical neuron
Large cell body with large, euchromatic nucleus with well-developed nucleolus
What part of dendrites are considered “plastic”?
Spines
Large, basophilic masses of free polysomes and RER
Nissl substance/bodies
Initial segment where excitatory or inhibitory stimuli are initiated on a neuron
Axon hillock
Distal end of axon, some of which have branching called collateral branches
Terminal arborization
Ends of axons usually have small _____ which are dilaterions of branch ends and contact the postsynaptic cell
Telodendria
Anatomy of chemical synapse
Presynaptic terminal bouton = contains mitochondria and synaptic vesicles which release NT via exocytosis
Synaptic cleft
Postsynaptic cell membrane = contains receptors for NT and ion channels to initiate new impulse
How is an electrical synapse different from a chemical synapse?
Electrical synapses permit direct, passive flow of electrical current from one neuron to another; current flows via gap junctions that link the pre and post synaptic membranes
Contain connexon proteins which permit diffusioin of small molecules and electric current flow
[whereas chemical synapses require NTs to diffuse across synaptic cleft]
3 primary types of glial cell
Astrocyte
Ependymal cell
Microglial cell
Oligodendrocytes
Functions of astrocytes
Helps form BBB Regulates ISF composition Structural support to CNS Helps neuronal dev’t Replicates to occupy space of dying neurons
Functions of ependymal cells
Lines ventricles of brain and central canal of SC
Assists in production and circulation of CSF
Functions of microglial cells
Phagocytic cells that move through CNS
Protects CNS by engulfing infectious agents and other potential harmful substances
Astrocytes have a large number of long, branching processes. Their proximal regions are reinforced with intermediate filaments made of ________
They form a vast network of delicate terminals contacting synapses+other structures.
GFAP (glial fibrillary acid protein)
Function of oligodendrocytes
Myelinates and insulates CNS axons
Allows faster AP propagation along axons in CNS
What glial cell type histologically appears as small cells with rounded, condensed nuclei and unstained cytoplasm/
Oligodendrocytes
Ependymal cell type
Columnar or cuboidal
Apical end may have cilia and long microvilli to facilitate movement or absorption of CSF
[joined apically by apical junctional complexes, there is no basal lamina]
Cell precursor to microglia
Monocytes
Histological distinctions of cell layers of cerebellar cortex
Molecular layer = much neuropil and scattered neuronal cell bodies
Purkinje cells = extend dendrites throughout molecular layer as branching basket of nerve fibers (conspicuous in H+E stained sections)
Granular layer = contains verious small densely packed neurons and little neuropil
Biologically older parts of the cerebral cortex, arranged into 3 layers
Archicortex
Most of the cerebral cortex consists of 6 layers and is caled the ____
Neocortex
The neocortex has a variety of cells, divided into what 5 morphological layers?
Pyramidal cells Stellate (granule) cells Cells of Martinotti Fusiform cells Horizontal cells of Cajal
Which morphological cell type of the neocortex is characterized by small neurons with a cell body in the shape of a star?
Stellate (granule) cells
Which morphological cell type of the neocortex is characterized by pyramid-shaped bodies with the apex directed towards the cortical surface?
Pyramidal cells
What are the largest pyramidal cells?
Huge UMNs of the motor cortex = Betz cells
Which morphological cell type of the neocortex is characterized by small polygonal cells with a few short dendrites?
Cells of martinotti
Which morphological cell type of the neocortex is characterized by small and spindle-shaped but oriented parallel to surface, and are the least common cell type?
Horizontal cells of Cajal
Which morphological cell type of the neocortex is characterized by spindle shaped cells oriented at right angles to the surface of the cerebral cortex?
Fusiform cells
What are the 6 cortical layers from superficial to deep?
- Molecular (plexiform) layer
- Outer granular layer
- Pyramidal cell layer
- Inner granular layer
- Ganglionic layer
- Multiform cell layer
Contents of molecular cortical layer (layer 1)
Dendrites and axons of cortical neurons
Sparse neuroglia and horizontal cells of Cajal
Contents of outer granular cortical layer (layer II)
Dense population of small pyramidal cells and stellate cells
Axons and dendrites from deeper layers
Contents of pyramidal cell cortical layer (layer III)
Pyramidal cells of moderate size predominate, martinotti cells also present
Contents of inner granular layer of cortex (layer IV)
Densely packed stellate cells
Contents of ganglionic cortical layer (layer V)
Large pyramidal cells and smaller numbers of stellate cells and cells of martinotti
Contents of multiform cell cortical layer (layer VI)
Wide variety of cell types (small pyramidal cells, cells of martinotti, stellate cells, and fusiform cells in deeper part)
The choroid plexus contains a thin layer of well-vascularized ____ mater covered by __________ cells
Pia; cuboidal
Choroid plexus has branching system of blood vessels which run in fronds composed of a fibrous core covered by _____ epithelium, forming a villous structure
Capillaries and vessels are large and thin walled. Epithelial cells rest on a _________
Long bulbous microvilli project from the epithelial cells
_____ _____ between epithelial cells contribute to a blood-CSF barrier
Cuboidal/columnar
Basal lamina
Tight junctions (zona occludens)
Structural classification of neurons and where they are found
Multipolar — most common, throughout CNS
Bipolar — sensory of retina, olfactory, and inner ear
Uni/pseudounipolar — sensory of DRG and cranial ganglia
Anaxonic — regulate electrical changes of adjacent neurons (no APs of their own)
____ = region where head of hippocampus abuts the dentate gyrus
Hilus
