neuro- dendrites and glia Flashcards
different types of cells present in the brain?
neurons
glial cells
what are ways of histologically staining neural tissue?
- fixation: brain tissue is fixed for preservation using paraformaledehyde and then embedded into wax/frozen material, so that you have a block ready to check under a microtome.
- sectioning: a microtome can cut slices of a block of embedded brain tissues into micrometers.
how can we visualise neural tissue?
the Nissl stain: comprised of a basic dye (cresyl violet) which stains the nuclei and the nissl bodies of the neuron.
nissl bodies are RNA rich structures such as the RER.
Golgi stain: comprised of a silver chromate solution, stains neurons and their projections.
some facts about light microscopy? and electron microscopy?
- has a resolution of 0.1 micrometer
space between neurons are 0.02 micrometer - electron microscopes have an resolution of 0.1 nanometre. All of the insights into the fine structure of the neurone has come from electron microscopy.
some more advanced techniques for observing parts of the brain?
- fluorescence microscopy and genetic manipulation techniques such as cre-lox
- enzyme which us cre, recognises some lox sites and inserts a fluorescent protein into the cells.
- allows researchers to look under the microscope and identify the areas of the brain with different colours.
what are neurones ?
information processing cells
highly specialised for the conduction and transmission of chemical and electrical signals
what does a prototypical neuron comprise of?
- cell body
- axon
-dendrites
describe the organelles contained in a cell body?
contains the same organelles found in all human beings
- nucleus
-RER
-SER
-Golgi apparatus
-mitochondria
describe the neuronal cytoskeleton?
-the cytoskeleton is the internal ‘scaffolding’ that gives a neurone its characteristic shape. Comprised of microfilaments, microtubules and neurofilaments.
Microtubules: a polymer of the protein tubulin. Located in axons and dendrites. Important for axoplasmic transport (transport of mitochondria lipids organelles proteins etc from the cell body to the axoplasm)
Microfilaments: a polymer of the protein actin, found throughout the neurone but particularly abundant in axons and dendrites.
Neurofilaments: a type of intermediate filament. Particularly abundant in axons and important in regulating atonal shape.
It is a promising biomarker for neurodegenerative disorders (eg Alzheimer’s)
Describe what an axon is and it’s types?
Axons are highly specialised neuronal projections that conduct nerve impulses within the nervous system
Axons are comprised of :
- axon hillock: tapers away from the cell body to form the initial part of the axon
- axon proper: axon can branch to form axon collaterals.
- axon terminal: site at which the axon comes into contact with another neurone at the synapse
function of glial cells?
glial cells are able to myelinate axons.
Myelin is a membranous sheath that is able to wrap around and insulate axons
Gaps in myelin sheath are called nodes of ranvier and are highly enriched in voltage gated sodium ion Chanels.
what are dendrites?
dendrites are highly specialised neuronal projections that recieve synaptic information from other neurones
Dendrites of a specific neurone are collectively termed as a dendritic tree
Dendrites of SOME neurones are covered with specialised structures called dendritic spines that are membranous sacs that protrude from the dendrites of some cells to receive synaptic input.
Dendritic spine structure is sensitive to type and amount of synaptic activity
A number of conditions have also been associated with abnormal dendritic spine number (Alzheimer’s, schizophrenia etc).
how can we classify neurones?
- either by neuronal structure or gene expression
classify neurones based on neuronal structure
number of projections- unipolar, bipolar, multipolar
number of dendrites - pyramidal, Stellate
connections: sensory, motor and intermediate.
axon length: Golgi type I (pyramidal) Golgi type II (stellate)
classify neurones based on their gene expression
neurones can be classified based on the type of neurotransmitter they release
-cholinergic (Ach)
-gabanergic (GABA)
- dopamine
- serotonin
-noradrenaline