Neurons & Glia Flashcards
Differentiate between neurons & glia
- Neurons do the “doing” (process information, sense environmental changes, communicate changes to other neurons, command body responses)
- Glia is the “glue” (insulate, support and nourish neurons)
What is meant by “the neuron doctrine”
The theory of a neuron as a structural & functional unit of the nervous system, adhering to cell theory & communicating by contact (in opposition to the previously held view of a continuous reticulum)
What are the features of a Nissl stain and what are it’s uses?
- stain that binds to ribosomes (found in nucleus & cytoplasm)
- pretty much just cell bodies - good for cytoarchitecture of CNS. Not good for morphology
What are the features of a Golgi stain & its uses?
- metal-based stain
- Stains entire cell membrane including dendrites/axons
- Only a small % of cells stained will take up the stain (we don’t know why)
- So v good for cell morphology
What are the major structural features of the soma?
Soma (cell body)
* large nucleus & lots of mitochondria
What are neurites?
combined name for dendrites & acons (branches coming off the neuron)
What are the 3 components of the cytoskeleton and their function?
- Microfilaments & Microtubules - give structural integrity
- Microtubules - highways to get stuff from soma to terminal & back
What are the 3 regions of an axon?
- Axon hillock - beginning, important for AP generation
- Axon proper - middle bit, carries AP
- Axon terminal - end, release of NT in response to AP
What are the differences between the axon and soma?
- ER does not extend into Axon
- axon has unique proteins to assist in AP conduction
What are the properties of the axon terminal cytoplasm?
- No microtubules in terminal
- Presence of synaptic vesicles
- abundance of membrane proteins
- lots of mitochondria (lots of processing happens at the terminal)
What are the 2 directions of axoplasmic transport?
- Anterograde (soma to terminal)
- Retrograde (terminal to soma)
What products get moved down the axon by axoplasmic transport?
- NT
- cellular machinery
- neuropeptides
- cytoskeletal structures
Differentiate between fast and slow axoplasmic transport
Fast:
* both directions
* movement of proteins within vesicles
* 100-400mm/day
* movement along microtubules
Slow:
* anterograde only
* movement of cytoskeleton/cytoplasmic components
* much slower - transport motor dynein
* for growth & maintenance
What are the major structural features of dendrites?
- dendritic spines - point of communication with other neurons.
- post-synaptic density on dendritic spines
What are the different ways neurons can be classified?
- # neurites (unipolar, bipolar, multipolar)
- morphology (stellate [star], pyramidal, spinous vs aspinous)
- CNS connection (sensory, motor, interneuron)
- axonal length (Golgi type I [long projection neuron], Golgi type II [short local circuit neuron])
- NT type (e.g. dopaminergic)
- by gene expression
What are the 4 main types of glia in the CNS?
- Astrocytes
- Oligodendrocytes
- Microglia
- Ependymal cells
What are the 2 main types of glia in the PNS?
- Schwann cells
- Satellite cells
What is the function of Astrocytes & key characteristics?
- Most numerous glia in the brain (around EVERY synapse and EVERY node of ranvier)
- Influence neurite growth
- fill space
- maintain electrochemical gradients, making NT, uptake of excess NT
- basically the only thing they dont do is electrical signalling
- cytoplasm has GFAP protein
What are 2 types of astrocytes?
- Fibrous astrocyte (in white matter)
- Protoplasmic astrocyte (in grey matter)
What can be seen when visualising astrocytes histologically?
Normally they look like daddy long legs but when we get neuroinflammation or injury they turn into big fat hairy tarantulas.
What is the function of oligodendrocytes?
myelination of CNA axons
What is the function of microglia?
- brain’s macrophase
- 5% of all glia
- become angry phagocyte-ish cells when CNS angry or diseased
- plus potentially other things like NT reuptake, release of cytokines, control of chemical environment
What is the function of ependymal cells?
makes CSF (takes blood plasma & filters out proteins)
What is a key functional difference between CNS and PNS?
Axonal regeneration is possible in the PNS (schwann cells promote regeneration by releasing growth factors).
In CNS, prolonged breakdown of damaged axons & ↑ astrocytes at site of injury → astrocytic scar/cyst actively preventing regeneration
