Cells of the nervous system Flashcards by Lilian Murnan

What is a neuron?

An excitable cell that conducts impulses

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What is the function of a neuron?

To integrate and relay information within a neural circuit

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What is Glia?

Supporting cells (Glue)

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What is the function of Glia?

Maintain homeostasis
Protection
Assist neural function

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What is Nissl staining used for?

Visualisation of size, density and distribution of neurons

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What does the soma contain?

Nucleus
Ribosomes, RER, Golgi apparatus
Mitochondria

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Potassium dichromate + Silver nitrate = ?

Silver chromate microcrystals

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What are the 4 major compartments of the neuron?

Cell body (soma)
Dendrites
Axons
Presynaptic terminal

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What is a microtubule composed of?

Polymers of tubulin

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Where are microtubules located?

Longitudinally down neurites

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What are microfilaments composed of?

Polymers of actin

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Where are microfilaments located?

Longitudinally
Membrane associated

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What are neurofilaments composed of?

Long protein molecules wound together

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What are the major components of an axon?

Axon hillock
Axon initial segment
Axon collaterals
Axon terminal

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Are there ribosomes on Axons?

No
No RER

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What does an axon with a high level of convergence equal?

= high levels of divergence

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What is the function of a synapse?

‘Fastens’ the pre and post synaptic vesicles together

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How is a presynaptic vesicle specialised to its function?

The cytoplasm contains no microtubules, synaptic vesicles, specialised proteins and mitochondria

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What is axoplasmic transport?

The flow of neurons from the soma to the axon terminal
Wouldn’t be possible via simple diffusion

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What is the distance moved by neurons via slow axoplasmic transport?

1mm per day

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What is the distance moved by neurons via fast axoplasmic transport?

1000 mm per day

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What molecules aid the movement of neurons in fast axoplasmic transport?

Neurons move along microtubules with the aid of ATPase kinesin

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Which direction does kinesin move towards?

The plus end of the microtubule (away from the cell body)

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How does retrograde transport occur in axons?

Via Dynein at a slower pace than Kinesin

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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