Cells of the nervous system Flashcards
What is a neuron?
An excitable cell that conducts impulses
What is the function of a neuron?
To integrate and relay information within a neural circuit
What is Glia?
Supporting cells (Glue)
What is the function of Glia?
Maintain homeostasis
Protection
Assist neural function
What is Nissl staining used for?
Visualisation of size, density and distribution of neurons
What does the soma contain?
Nucleus
Ribosomes, RER, Golgi apparatus
Mitochondria
Potassium dichromate + Silver nitrate = ?
Silver chromate microcrystals
What are the 4 major compartments of the neuron?
Cell body (soma)
Dendrites
Axons
Presynaptic terminal
What is a microtubule composed of?
Polymers of tubulin
Where are microtubules located?
Longitudinally down neurites
What are microfilaments composed of?
Polymers of actin
Where are microfilaments located?
Longitudinally
Membrane associated
What are neurofilaments composed of?
Long protein molecules wound together
What are the major components of an axon?
Axon hillock
Axon initial segment
Axon collaterals
Axon terminal
Are there ribosomes on Axons?
No
No RER
What does an axon with a high level of convergence equal?
= high levels of divergence
What is the function of a synapse?
‘Fastens’ the pre and post synaptic vesicles together
How is a presynaptic vesicle specialised to its function?
The cytoplasm contains no microtubules, synaptic vesicles, specialised proteins and mitochondria
What is axoplasmic transport?
The flow of neurons from the soma to the axon terminal
Wouldn’t be possible via simple diffusion
What is the distance moved by neurons via slow axoplasmic transport?
1mm per day
What is the distance moved by neurons via fast axoplasmic transport?
1000 mm per day
What molecules aid the movement of neurons in fast axoplasmic transport?
Neurons move along microtubules with the aid of ATPase kinesin
Which direction does kinesin move towards?
The plus end of the microtubule (away from the cell body)
How does retrograde transport occur in axons?
Via Dynein at a slower pace than Kinesin
Why would retrograde transport occur in an axon?
To enable target derived growth factors to reach their target
e.g. a nerve growth factor to reach the nucleus in order to aid survival
What molecules use slow axoplasmic transport?
Soluble proteins used as enzymes for intermediary metabolism
Cytoskeletal proteins
What is the main difference between slow and fast axoplasmic transport?
The number of interruptions (more in slow)
What technique is used to manipulate axoplasmic transport to visualise cells?
Injecting HRP in the brain ->
2 days later, after retrograde transport has occurred, HRP will label neurons
What are multiple dendritic branches converging together called?
Dendritic trees/arbors
What is the function of a dendritic spine?
To amplify the postsynaptic vesicles area to increase surface area
Nissl stain: colour, identification
Cresyl violet
Neurons vs glia cytoarchitecture
Golgi stain: colour, identification
Silver chromate
Highlights some neurons
Neuron doctrine (individual neuronal cells)
Immunohistochemistry: identification, process
Fixed tissue
Antibodies
Fluorescent microscope
How is live imaging of fluorescent dye carried out?
Genetically or injected
What does the electron microscope display?
Synapses and organelles
What is a retrograde tracer and what is its purpose?
HRP (identifies retrograde transport in axons)
Finds cell body location
How can you classify neurons?
By structure
By gene expression
How would neurons be classified by structure?
Number of neurites
Dendritic geometry
Projection of connections
Axon length
How would neurons be classified by gene expression?
Underlying structural differences
Defining neurotransmitter expression
What is a unipolar neuron?
One process
The peripheral process is part axon too
Small area for receiving synaptic input
Example of a unipolar neurite
Dorsal root ganglion
What is a bipolar neuron?
Two processes extending from opposite sides of the body
Small area for receiving synaptic input
Example of bipolar neuron
Retinal bipolar cells
What is a multipolar neuron?
Many dendritic processes
Large area for receiving synaptic input
High levels of convergence
Function of relay/projection neuron?
Connect brain regions
Function of local interneurons?
Process info in local circuits
Function of Glia cells?
Fill the space around neurons (act as glue)
What is an astrocyte?
A type of glial cell (radial glia cell) which holds a neuron in place
Control environment surrounding neurons
Spatial domains
What are 6 subtypes of glial cells?
Fibrous
Protoplasmic
Radial
Muller
Bergmann
Ependymal
What can astrocytes metabolise and supply?
Glycogen and lactate
What is classed as a glycogen store of the brain?
Astrocytes
What does an astrocytic endfoot take up?
Glucose
How long is the supply of glycogen given by astrocytes?
5-10 mins
What is a tripartite synapse function?
Terminates neurotransmitter activity
Recycles neurotransmitters to presynaptic vesicles
What do astrocytes couple neuronal activity to?
Couple neuronal activity to blood supply
What do astrocytes couple neuronal activity to?
Couple neuronal activity to blood supply
What is a microglia?
A macrophage like glia which prunes the synapses
What is synaptic pruning?
A Homeostatic function in the CNS which gets rid of synapses which aren’t in frequent use
What is the reason for synaptic pruning?
To remove unnecessary neuronal structures from, the brain
Makes way for more complex and developed structures
What is an oligodendrocyte?
The cells that form the myelin sheath of CNS axons
What cells form the myelin sheath of the PNS?
Schwann cells
What does a Schwann cell provide to a single axon?
A single myelin segment
How is a myelin sheath formed?
Oligo cytoplasm wraps many times around the axon
Cytoplasm is squeezed out by compaction of layers
Why do myelin sheaths maintain contact with glial cells?
Nourishment
What is myelin’s function?
Insulation
Creates nodes of ranvier
What is saltatory conduction?
Axons have gaps on them (nodes of ranvier) which allow electrical signals to ‘jump’ from node to node and increase the speed of their signal
What are homeostatic cells in PNS called?
Satellite cells
What are homeostatic cells in CNS called?
Astrocytes
What are homeostatic cells in ENS called?
Enteric glia
What are myelinating cells in CNS called?
Oligodendrocytes
What are myelinating cells in PNS called?
Schwann cells
What are phagocytic cells in CNS called?
Microglia
What are phagocytic cells in PNS called?
Schwann cells and Macrophages
