Neurocytology Flashcards
Macroglia
- astroglia
- oligodendrocytes
- oligodendrocyte precursor cells (NG2 cells)
- ependymal cells
From which germ layer did microglia originate from?
mesoderm
gray matter
neuronal cell bodies and glia
white matter
myelin-ensheathed axons
lipids
hemotoxylin/eosin staining
nucleus/cytoplasm
Nissl staining
nucleus
RER
RNA granules
unipolar vs. bipolar vs. multipolar neurons
unipolar –> sensory neurons
bipolar –> interneurons
multipolar –> motor neurons
motor neuron
single axon
multiple dendrites
pyramidal neuron
single axon basal dendrites (directly off soma) apical dendrites (br. off of a branch from soma, even more br. after)
purkinje neuron
huge dendrite tree to receive massive amounts of inputs
peripheral glia cells
Schwann cells (prod. myelin)
fast rate of conduction
large/small axon?
(thick/thin myelin sheath?)
(long/short distance between nodes of Ranvier?)
LARGER axon
THICKER myelin sheath
LONGER distance between nodes
–> FASTER rate of conduction
what determines the potential input that a neuron can receive/controls synapse strength?
number/shape of dendrites and dendritic spines
types of synaptic contacts
axodendritic synapse
axosomatic synapse
axoaxonic synapse
conserved properties of in vivo mature grey matter astroglia
NON-electrically excitable, very low input-resistance
homeostatic function –> uptake glutamate through excitatory amino acid transporters (EAATs)
highly ramified cellular processes
extensive intercellular coupling though gap-junctions
tripartite synapse
synapse has an astrocyte component
astrocytes respond to synaptic signals w/ Ca++ excitability –> slower
astrocyte functions in CNS
- metabolic support (support nutrients)
- structural support
- homeostatic functions
- NT removal (glutamate)
- K+ regulation in extracellular spaces - glymphatic system
- synaptic modulation (secrete active transmitters)
- synapse formation modulation (secrete extracellular matrix proteins –> synaptogenesis)
glutamate-glutamine cycle
when glutamate is released –> excites neurons
excess glutamate –> picked up by glial cells (EAAT) –> conversion to glutamine –> transported back to neurons
key point=neurons don’t need to replenish glutamate every time
Why can’t axons regenerate?
injury causes astrocytes to become GFAP+ and form glial scars –> axons can’t reconnect
How are certain reactive astroglia toxic?
Some can secrete toxic factors that induce neuronal cell death.
astrocytoma
major source of brain glioma
key functions of microglia
surveillance
cluster around amyloid plaques
become active to release cytokines + carry out PHAGOCYTIC activities
high motility
glial specific genes that predispose general population to Alzehimer’s disease
APOE
TREM2
genes that cause Alzehimer’s disease but are VERY RARE in general population
PSEN
APP
key functions of oligodendrocytes
myelin formation in CNS
*prevents leakage of current, maintains conduction velocity of AP
key functions of Schwann cells
myelin formation in PNS
(basically a peripheral oligodendrocyte)
*prevents leakage of current, maintains conduction velocity of AP
glial cells vs. neurons
total amounts in whole brain?
Glial cells are roughly equal to number of neurons comprising CNS.
Ratio varies in dif brain regions.
