Cells of the Nervous System Flashcards
what is the basic structural and functional unit of the nervous system?
Neurone
how is neurone cell diversity of morphology achieved?
different number and shape of processes, determined by function and location.
note this makes neurones more vulnerable to degenerative disorders like alzheimers.
features of a neurone
- large nucleus
- prominent nucleolus
- lots of RER and Golgi
- lots of mitochondria
- highly organised cytoskeleton
Highly organised and very metabolically active secretory cell (lots of protein trafficking)
what do Dendrites do?
- input information
- branch frequently allowing integration of signals
- contain many spines which is where synapses occur
describe the structure of a pyramidal cell
4 points of cell body. 3 primary dendrites off which secondary dendrites arise. One long axonal projection.
most plastic area of a neurone?
dendrites as can make many different spines hence synaptic pathways
spines synapse with?
many other neurones
what are purkinje cells?
cells of the cerebellum, look like a tree, planar cells, heavily branched but linear when looked from side
what is an axon?
output impulses away from cell body and axon hillock
it contains prominent microtubules and neurofilaments
why are axons the same diameter throughout?
to maintain the same speed of impulse throughout
why are microtubules and neurofilament needed in an axon?
neurofilament for strength
microtubules for vesicular transport
the axon has nodes of ranvier made by myelination, what is the structure of the node?
the node itself contains only sodium ion channels.
next to it is the paranode where the schwan cell attaches
next to that is the juxtanode where there are potassium ion channels.
types of axon terminals
boutons (bulge at the end of an axon)
varicosities (bulges along axon where neurotransmitter released)
how are different impulses integrated?
different transmitters cause different amounts of depolarisation of the dendrites. these signals are summated and processed by the post synaptic neurone
types of synapse?
- axo-dendritic (excitatory)
- axo-somatic (inhibitory)
- axo-axionic (modulatory)
how long can axons be?
micrometers to a metre
what makes the neurofilament cytoskeleton strong?
many cross bridges, the more neurofilament, the better the axon calibre.
what types of transport is there within an axon?
retrograde: vesicles transported towards cell body
anterograde: movement towards the synapse (away from cell body)
to differentiate, they are morphologically and biochemically different to allows recognitions by only certain compartments
what happens in multiple sclerosis?
demyelinating neuropathy
types of morphology of neurone
- unipolar
- bipolar (retinal)
- psuedunipolar (dorsal root ganglion)
- Golgi Type I multipolar
- Golgi type II multipolar
features of golgi type I cells (purkinje and pyramidal)
- highly branched dendritic tree
- long axons
- most vulnerable to degradation eg ataxia
features of golgi type II cells (stellate cells of cobra cortex and cerebellum)
- highly branched dendritic tree
- short axons
function of interneurones
responsible for: • modification • integration • facilitation • coordination • inhibition
of sensory inputs
what are neuroglia?
non excitable support cells of the nervous system needed for correct functioning of neurones.
what are immature progenitors neuroglia for?
regeneration
what are astroglia?
fibrous astroglia in white matter
proteoplasmic astroglia in grey matter
They signal eachother through Gap junctions in continuity in reaction and signalling
involved in homeostasis as foot processes scan microenvironment and react specifically.
function of astroglia?
- scaffold for neuronal migration and growth
- formation of BBB (glia limitans)
- transport substances from blood to neurones
- create synapses
- removal of excess ions or neurotransmitter and water
- glial scar formation
- synthesis of neurotrophic factors
what are oligodendroglia?
production and maintenance of myelin sheath of many neurones in the CNS
what are microglia?
- derived from bone marrow
- immune function (inflammation)
- acts as a macrophage and is first to respond in brain infection
- changes morphology from processes to blob when activated
- needed for tissue remodelling
- synaptic stripping
what are peripheral glia?
schwann cells, each produces only one myelin sheath in PNS. they are also needed for axon regeneration.
