Neurons and Glial Cells Flashcards
where does the axon arise from
axon hillock
what is the axoplasm and what does it lack
axonal cytoplasm
lacks RER and Golgi
why must materials be transported back and forth between the cell body and terminus
lacks components for synthesising new proteins and degrading old ones
fast component of axonal transport
50 - 400 mm/day
transports cytoplasmic proteins and macromolecules
slow component of axonal transport
1 - 4 mm/day
transports cytoskeletal components
number of glial cells vs neurons
10x more
Anterograde transport
Retrograde transport
Anterograde transport is forward, away from cell body
Retrograde transport is transport towards the cell body
contents of dendrites
all cytoplasmic components found in the cell body except the Golgi apparatus
function of dendritic spines
increase surface area
pre-synaptic membrane
thickened region in the plasmalemma
contains voltage-gated Ca2+ channels
arrival of an action potential at an axon terminal
opening of Ca2+ channels
triggers exocytosis of the neurotransmitters
synaptic cleft size
20 - 40 mm
postsynaptic membrane
thickened region in the plasmalemma
excitatory synapses contains voltage-gated Na+ channels
inhibitory synapses contains voltage-gated K+ or Cl- channels
what generally results from damage to the cell body of a neuron
why
cell death
cannot undergo cell division
what is the initial result of severing or crushing of an axon
cell body swells and nucleus is displaced peripherally
chromatolysis
chromatolysis
after axonal damage, Nissl bodies disperse with a concomitant loss in the cytoplasmic basophilia
Wallerian degeneration
anterograde degeneration after from the site of injury
Axon swells and degenerates causing fragmentation of myelin sheath which are removed b phagocytes
schwann cells in axonal damage
can proliferate and form a tube distal to the injury
causes axon to regain function
takes 3 weeks
lesion in peripheral neuron
axonal sprouts
axon stump
oligodendrocytes overview
60 - 80% of glial cells
myelin sheath formation
astrocyte overview
25% of glial cells
BBB
structural support and scar formation
secretion of growth factors
water transport
excess transport -> cerebral oedema
microglia overview
5-10% of glia cells
brain macrophages
secretion of inflammatory cytokines and chemokines
APCs
astrocyte pedicles
end feet that terminate on capillaries/pia matter
fibrous astrocytes
located primarily in white matter
long spindly processes with few branches
protoplasmic astrocytes
located in grey matter
thick, lightly branched processes closely apposed to neuron somas
functions of astrocytes
regulation of intercellular environment
structural support
metabolise neurotransmitters
mediate exchange of nutrients and metabolites between blood and neurons
form glial scar after CNS injury
tripartite synapse
oligodendrocytes in white and grey matter
white matter: predominant glial cell, produce myelin sheath
grey matter: closely associated with cell bodies functioning as satellite cells and anchor cell bodies
what is the PNS composed of
neuron processes of CNS neurons and PSN neural cells
Schwann cells and satellite cells
nerve endings
peripheral nerve structure
fascicles of nerve fibres surrounded by myelin sheaths and connective tissue
epineurium, perineurium and endoneurium
epineurium
connective tissue surrounding entire nerve
perineurium
layer of dense connective tissue around each fascicle
endoneurium
thin reticular layer surrounding each individual nerve fibre
contains Schwann cells
lies outside and encloses the myelin sheath
number of axons myelinated by ODGs vs Schwann cells
ODGs myelinate portions of several axons
Schwann cells myelinate portions of a single axon
ganglia
what do they contain
encapsulated collections of neuron cell bodies located outside CNS
contain satellite cells, connective tissue elements and neurons
ganglia satellite cells
amphicytes
glial cells that form a capsule of cells around neural cell bodies
