neurology cells Flashcards
neurons - function
signal-transmitting cells of the nervous system
neurons - proliferation status
permanent cells - do not divide in adulthood
neurons - structure and function of every part
signal relaying cells
dendrites - receive input
cell bodies
axons send input
neurons cell bodies and dendrites can be seen on
Nissle staining (stains RER)
in neurons cells, Nissle stains …. (part) why
Cell bodies and dendrites, not the axon because there are not RERs
Injury of axon of neuron –> .. ..
Wallerian degeneration: degeneration distal to injury and axonal retraction proximally
Wallerian degeneration - purpose
allows for potential regeneration of axon (if in peripheral)
astrocytes - marker and origin
marker: GFAP
origin: neuroectoderm
astrocytes - function
- physical support
- repair
- removal of excess neurotransmitter
- component of BBB
- glycogen fuel reserve buffer
- K+ metabolism
- reactive gliosis in response to neural injury
astrocytes - response to neural injury
Reactive gliosis
Microglia function / origin
Phagocytic scavenger cells of CNS
origin: mesodermal, mononuclear origin
Microglia - activation
in response to tissue damage
Microglia - staining
not readily discernible by Nissl stain
Microglia vs HIV
microglia infected by HIV fuse to form multinucleated giant cells in CNS
Myelin is made of
- CNS - oligodendrocytes
- PNS - Schwann cells
Myelin - mechanism of action
Wraps and insulates axons –> saltatory conduction of action potential at nodes of Ranvier, where there are high concentrations of Na+ channels –> increases 1. space constant 2. conduction velocity
condition that destroys Schwann cells
Acute inflammatatory demyelinating polyradiculopathy (Guillain-Barre syndrome)
Schwann cells - derived from
neural crest
Schwann cells - function / origin
- myelinates PNS axon
- promote axonal regeneration
origin: neural crest
nobes of Ranvier - high concentration of
Na+ channels
astrocytes, microglia, Schwann cells, oligodendroglia - derived from
astrocytes –> neuroectoderm
microglia –> mesodermal, mononuclear origin
Schwann cells –> neural crest
oligodendroglia –> neuroectoderm
Acustic neuroma - if bilateral, strongly associated with…. / typically located
NF2
typically located in internal acoustic meatus (CN III) –> may extend to cerebellopontine angle
oligodendrocytes - histological appearance and function
fried egg
myelinates axins of neurons in CNS
oligodendrocytes VS Schwann cells according function
- Schwann myelinates PNS axons while oligodendrocytes axons in CNS
- One Schwann myelinates 1 axon while oligodendorcyte a lot (~30)
conditions with injured oligodendroglia
- multiple sclerosis
- progressive multifocal leukoencephalopathy
- leukodistrophies
peripheral nerve structure - from outer to inner
Epineurium - perineurium - endoneurium
peripheral nerve structure - epineurium?
dense connective tissue that surrounds entire nerve (fascicles and vessels)
peripheral nerve structure - perineurium?
surrounds a fascicle of nerve fibres
Predominant type of glial cells in white matter
oligodendrocytes
peripheral nerve structure - endoneurium?
invests single nerve fibers layers
peripheral nerve structure - for limb reattachment
perineurium must be rejoined microsurgery
peripheral nerve structure - inflammatory infiltrate in Guillain Barre syndrome
endoneurium
BBB function
prevents circulating blood substances (eg. bacteria, drugs) from reaching CSF/CNS
BBB - number of structures and structures
3 structures:
- tight junctions between nonfenestrated capillary endothelial cells
- Basement membrane
- Astrocyte foot processes
example of substances that crosses BBB and how
glucose –> slowly by carrier-mediated transport mechanism
amnoacids –> slowly by carrier-mediated transport mechanism
Nonpolar/lipid-soluble –> rapidly via diffusion
CNS - fenestrated capillaries
a few specialized brain regions with fenestrated capillaries and no blood-brain barrier allow molecules in blood to affect brain function
CNS - fenestrated capillaries - functional anatomy examples
- area postrema ( medullary structure) - vomiting after chemo
- Vascular organ of lamina terminalis - osmotic sensing
- neurosecretory products (ADH - neurohypophysis)
Beside BBB, other notable barriers includes
Blood-testis barrier
Maternal-fetal blood barrier of placent
Vasogenic edema mechanims
cerebral edema in which the BBB is disrupted (damaged endothelial cell tight junction)
Vasogenic edema - causes
- infraction
2. neoplasm
Osmotic demyelination syndrome is also called
central pontine myelinolysis
Osmotic demyelination syndrome (central pontine myelinolysis) can cause
- acute paralysis 2. dysarthria 3. dysphagia
4. diplopia 5. loss of consciousness 6. locked in syndrome
locked in syndrome - definition
body and most of the facial muscles are paralysed but consciousness remains and the ability to perform certain eye movements is preserved.
Osmotic demyelination syndrome (central pontine myelinolysis) - pathophysiology
massive axonal demyelination in pontine white matter secondary to osmotic damage
Osmotic demyelination syndrome (central pontine myelinolysis) - MCC
iatrogenic - overly rapid correction of hyponatremia
correcting hypernatremia too quickly results in
cerebral edema/herniation
correcting of serum Na+ too fast can cause
from low to high –> Osmotic demyelination syndrome
from high to low –> cerebral edema/herniation
CNS - fenestrated capillaries - functional anatomy examples
- area postrema ( medullary structure) - vomiting after chemo
- Vascular organ of lamina terminalis - osmotic sensing
- neurosecretory products (ADH - neurohypophysis)
