Histology of the CNS Flashcards
What is a neuropil?
Dense network of nerve fibers and their branches and synapses, together with glial filaments
What is anterograde transport?
Carries material from the nerve cell body to the axon; utilizes kinesin, a microtubule-associated motor protein
What is retrograde transport?
Carries materal from the axon terminal to the cell body or dendrites to the cell body; utilizes dynein, a microtubule-associated motor protein
Describe slow transport
Anterograde movement of substances; speed of .2-.4 mm/day; typically cytoskeletal elements
Describe fast transport
Bidirectional movement of organelles; speed of 20-400 mm/day; retrograde may include endocytosed toxins and viruses
What does a presynaptic terminal bouton contain?
Mitochondria and synaptic vesicles that release neurotransmitters via exocytosis
What does a postsynaptic cell membrane contain?
Receptors for the neurotransmitter and ion channels to initiate a new impulse
Describe an electrical synapse
Direct, passive flow of electrical current between neurons via gap junctions; link pre and post-synaptic membranes; contain connexon proteins that link pre- and post-synaptic membranes
What do astrocytes do?
Form a network of delicate terminals contacting synapses and other structures; terminal processes of a single astrocyte typically associate with 1 million + synaptic sites
The proximal regions of astrocytes are reinforced with what?
Glial fibrillary acid protein (GFAP)
What do olingodendrocytes do?
Extend processes that enwrap nearby axons in myelin; enwrap axons from multiple neurons
Describe ependymal cells
Columnar or cuboidal cells that line the brain ventricles and central canal of the spinal cord; apical end have cilia and long microvilli that facilitate movement of CSF and are likely involved in absorption; joined apically by apical junctional complexes; no basal lamina present
What is the choroid plexus and what does it do?
Folded layer of pia mater covered by cuboidal ependymal cells; removes H2O from blood and releases it as CSF; contains Na, K, and Cl, very little protein, and sparse lymphocytes
Where is the choroid plexus located?
Completely fills ventricles, central canal of spinal cord, subarachnoid space, and perivascular space
What are microglia and what do they do?
Originate from monocytes; will remove damaged or unactive synapses or other fibrous components and is the major mechanism of immune defense in the CNS, removing any microbial invaders
Describe the spinal cord
Has a central mass of gray matter with ventral, lateral, and dorsal horns; central canal lies in the central commissure and is lined by ependymal cells and contains CSF; white matter consists of ascending tracts of sensory fibers and descending motor tracts
What are the 3 layers of the cerebellar cortex?
Molecular, purkinke cells, granular; organized into folia with the cerebellar medulla located deep
Describe the molecular layer of the cerebellar cortex?
Many neuropil and scattered neuronal cell bodies
Describe the purkinje cell layer of the cerebellar cortex?
Extend dendrites throughout the molecular layer as a branching basket of nerve fibers
Describe the granular layer of the cerebellar cortex?
Contains various very small, densely packed neurons and little neuropil
What is the older part of the cortex called and how many layers does it have?
Archicortex, 3 layers
What is the majority of the cortex called and how many layers does it have?
Neocortex, 6 layers
What are pyramidal cells?
Pyramid-shaped cell bodies with the apex directed towards the cortical surface; huge upper motor neurons of the motor cortex (Betz cells) are the largest
What are granule (stellate) cells?
Small neurons with a cell body the shape of a star (look like granules on micrographs)
What are Cells of Martinotti?
Small polygonal cells with a few short dendrites
What are fusiform cells?
Spindle-shaped cells oriented at right angles to the surface of the cerebral cortex
What are Horizontal Cells of Cajal?
Small and spindle-shaped but oriented parallel to the surface (least common)
What cells are found in the cerebral cortex?
Pyramidal, granule (stellate), Cells of Martinotti, fusiform, Horizontal Cells of Cajal, astrocytes, oligodendroglia, and microglial cells
What are the 6 cortical layers of the neocortex from superficial to deep?
Molecular, external granular, external pyramidal, internal granular, ganglionic, and multiform (polymorphic) layers
What is the molecular layer of the neocortex?
Consists largely of fibers, most of which travel parallel to the surface, and mostly neuroglial cells and Horizontal Cells of Cajal
What is the external granular layer of the neocortex?
Consists mainly of small pyramidal cells and granule cells
What is the external pyramidal layer of the neocortex?
Pyramidal cells are somewhat larger and possess a typical pyramidal shape; not sharply demarcated from layer 2
What is the inner granular layer of the neocortex?
Characterized by the presence of many small granule cells
What is the ganglionic layer (inner pyramidal layer) of the neocortex?
Contains pyramidal cells that are extremely large (Betz cells) in motor areas
What is the multiform (polymorphic) layer of the neocortex?
Contains cells with diverse shapes, many of which are fusiform cells
What are the symptoms of Alzheimer’s?
Memory failure, progressing steadily to involve motor skills, speech, and sensation
What is the substantia nigra?
Large mass of gray matter containing multipolar neurons w/ dark pigment; has connections with the cortex, spinal cord, corpus striatum, and reticular formation; plays important role in fine control of motor function
What is neuromelanin pigment and where is this found?
Contains dopamine, which has inhibitory effects in brain areas dedicated to movement; found in substantia nigra
What are the clinical features of Parkinson’s?
Tremor, slow movement, and rigidity resulting from degeneration of neurons in the substantia nigra, which leads to a loss of dopamine
What are some things associated with Parkinson’s?
Lewy bodies and alpha-synuclein proteins
What are some things associated with Alzheimer’s?
Amyloid beta plaques and neurofibrillary tangles
What is the most common neurodegenerative disease?
Alzheimer’s
