Neurone cells Flashcards
What classes can neural cells be split into?
neurons
differentiated glia
- ogliodendrocytes
- microglia
- astrocytes
other glial cells
Where are inputs into neurones?
dendrites
Where are action potentials propogated from?
axon hillock, then down the axon
What are the 2 types of synapses?
chemical - use neurotransmitters, bind to receptors
electrical - much less - channels that allow direct flow of current -
Cell make up at synapses?
MANY proteins for receptors - electron dense material on TEM
mitochondria for energy to pass neurotransmittors
Why are electrical synapses important?
important for synchronised electrical activity
How does chemical synaptic transmission work?
axon potential depolarises synaptic terminal membraneS
Structure of electrical synapses
lots of electron dense material - gap junctions - continuous channel allows transmission of ions and currents
Where are most excitatory sysnapses?
often concentrated on dendritic spines
What is neural plasticity?
changes in neronal/synaptic structure ans function in respinse to neural activity
spines are dynamic structures - number, size, composition
spine remodelling linked to neural activity
What are betz cells? (upper motor neurones)
upper motor neurons - large excitatory (glutamatergic)
long projectiions, pyramidal cells
vulnerable in motor neurone disease
What are medium spiny neurones?
striatal interneurons
small, inhibitory, (GABAeric)
vulnerable in huntigtons disease
What are ogliodendrocytes?
myelinating cells of the CNS
enables rapid nerve conduction
Myelin sheath interrupted by nodes of Ranvier
they also provide metabolic support for the axons (lactate transporters)
What is saltatory conduction?
propogation of an impulse across nodes of Ranvier due to myelination
How is the myelin sheath formed?
ogliodendrocyte processes wrap around axons
Highly compacted - 70% lipid, 30% protein
Myelin specific proteins and be used as markers - very specialised proteins
Microglia?
originate from different palce embryologically
resting state is highly ramified, motile processes survey environment
on activationm retract processes, become amoeboid and motile
are prolifereative
What are the functions of microglia?
immune surveillance
phagocytosis - debris, microbes
synaptic plasticity - pruning of spines
‘bad’ and ‘good’ microglia - some more antiinflammatory
What are astrocytes?
‘star-like’ cells
most numerous glial cells in CNS (similar numbers to neurons)
highly heterogeneous -morphology is variable - not all star shaped
contribute to blood brain barrier
How do astrocytes contribute to the blood brain barrier?
processes of the astrocytes wrap around of the capillaries
express proteins for specialised water channels
Functions of astrocytes?
structurally they define the brain mico-architecture
metabolic support - e.g. Glutamate-Glutamine shuttle
neurovascular coupling - changes in cerebral blood flow (vasodilation+) in response to neural activity
envelop synapses - buffer K+, glutamate etc
Proliferate during disease
important in scarring of CNS
Other specialised glia?
radial cells - important for brain development
bergmann glia in cerebellum
Muller cells - scaffold for other cells to form in the retina
Brief description of motor neurone disease?
Loss of motor neurons in upper cortex and lower spinal cord - pathological changes in all neural cell types though
Brief description of MS?
Damaged ogliodendrocytes - are attacked - this is where the primary pathology is
acute symptoms relfect dysfunction of the neurons
Where are axons gathered? in cns
Where is PNS?
tracts
bundled into nerves
What are tracts that cross the midline called?
tracts are gathered axons
commissures
What id the difference in myelination between CNS and PNS?
ogliodendrocytes in brains and spinal cord
schwann cells in peripheral
How is the blood brain barrier formed?
endothelial cell tight junctions
basement membrane (few fenestrations)
astrocyte end feet
pericytes
What are ependymal cells?
line ventricles and central canal of the spinal cord
involved in CSF production, flow and absorption
ciliated to facilitate flow
allow solute exchange between nervous tissue and \CSF
