2/ cells of the nervous system Flashcards
what are glia
- supporting cells to neurons
- glue holding them together
- maintain homeostasis, protection, assist neural function
- keep neurons alive and healthy
- space around neurons filled by glia
organisation of neural systems
cells (neurons and glia), neural circuits, neural systems
how many neurons and glia
about 85 billion of each type
Nissl staining
- developed Nissl staining to distinguish between neurons and glia
- nucleolus of all cells stained - binds to RNA
- neurons also have Nissl bodies
- cresyl violet
- cytoarchitecture
soma
- aka cell body/perikaryon
- contains nucleus
- contains organelles for protein synthesis and processing (ribosomes, rough ER, Golgi apparatus)
- contains mitochondria - use lots of ATP for AP
Golgi stain
- silver chromate
- stains a small % of neurons with greater detail than Nissl
- entire cell membrane stained black
- neuron doctrine - NS made of discrete cells
importance of Cajal (man)
- mapped neurons
- discovered neurons were distinct - not physically linked (as Golgi thought)
- realsied there was a small gap between them
4 major compartments of neuron
- cell body/soma/perikaryon
- neurites - dendrites, axon
- presynaptic terminal
how do microtubules form the cytoskeleton of neurons
- longitudinally down neurites (must be v stable - some neurons spine to foot)
- hollow tube composed of polymers of tubulin
parts of axon
- axon hillock connects axon to cell body
- axon initial segment after hillock, where AP is propagated, lots of ion channels
- axon collaterals - branches. thinner than main axon, allow signal to reach multiple targets.
- axon terminal/terminal bouton
features of axons
- no rough ER or fewer (not 0) free ribosomes
- different membrane composition
- <1mm to >1m in length
- 1um -25um in diameter
immunohistochemistry
- primary antibody binds to protein of interest
- secondary fluorescent antibody binds to primary
- can use different colours at once - if all proteins present will appear white
- fixed tissues
- fluorescent microscope
method to allow you to see specific neuron and its neurites?
dye in pipette inserted into neuron
axons
- thicker
- may be myelinated
- many collaterals = high levels of divergence (coordinate response across multiple areas)
specialisation of terminal cytoplasm
- no mictrotubules
- synaptic vesicles
- specialised proteins
- lots of mitochondria
boutons en passent
presynaptic terminal not at the end of an axon
terminal arbour
fine branches of axon towards the end of the axon
what is slow axoplasmic transport, how was it discovered
- discovered by tying a knot
- bit closest to cell body above knot started to bulge
- direction: cell body to axon terminal
- slow - can’t be the only thing happening
fast axoplasmic transport
- discovered by radioactive amino acids
- 1000 mm per day
- microtubules, kinesin (walks along microtubules carrying vesicles packaged with proteins) and ATP - anterograde transport
- retrograde transport by dynein
anterograde and retrograde directions
- anterograde cell body to terminal
- retrograde terminal to cell body
how can axoplasmic transport be manipulated to visulise cells
- Can show anterograde or retrograde labelling
- eg inject HRP into foot muscle. Dynein will carry back to cell bodies, so we know its a motor neuron, retrograde
- find cell body location
dendrites
- dendritic branches together form dendritic trees/dendritic arbours
- convergence: multiple inputs can converge on one neuron - enough info to decide on output
- can have thousands of synapses
- live florescent imaging to visualise - genetic or injected fluorescent dye
dendritic spines
- tiny protrusions from dendrites, form connections with axons
- dynamic, flexible, appear and disappear
- plastic
- isolate chemical reactions?
- abnormalities mean cognitive impairment
