Neuro - Neurons And Glia Flashcards
What is the brain comprised of?
The human brain is comprised of both neurons and glial cells
What are the two different processes used to analyse the brains micro anatomical features?
histological staining of neural tissue
- Fixation: Brain tissue is fixed for preservation and subsequently embedded
- Sectioning: A microtome can cut slices from a block of embedded brain tissue
How can we visualise neural tissue?
Via the Nissl stain and the Golgi stain
Describe the Nissl stain
- Comprised of a basic dye
- Stains the nuclei and Nissl bodies of neurons
Describe the Golgi stain
- Comprised of a silver chromate solution
- Stains neurons and their projections
What is the significance of these dye’s today?
- Fluorescence microscopy and genetic manipulation techniques allow us to see brain regions and individual neurons/glial cells in breath-taking detail
What is a neuron?
- Neurons are the information processing cells within the nervous system
- They’re highly specialised for the conduction and transmission of electrical and chemical signals
What does a neuron comprise of?
- Cell body
- Axon
- Dendrites
Describe what the cell body contains
Contains the same organelles found in all human cells:
- Nucleus
- Rough endoplasmic reticulum
- Smooth endoplasmic reticulum
- Golgi apparatus
- Mitochondria
What does the neuronal cytoskeleton consist of?
- Cytoskeleton
- Microtubules
- Microfilaments
- Neurofilaments
What is the cytoskeleton?
- The internal scaffolding that gives neurons it’s characteristic shape
- Comprised of microtubules, microfilaments and neurofilaments
What are microtubules?
- A polymer of the protein tubulin
- Located in the axons and dendrites
- Important in axoplasmic transport
What are microfilaments?
- A polymer of the protein actin
- Found throughout the neuron
- But are abundant in axons and dendrites
What are neurofilaments?
- A type of intermediate filament
- Particularly abundant in axons
- Important in regulating atonal shape
- Promising bio marker for neurodegenerative disorders
Describe what an axon is
Axons are highly specialised neuronal projections that conduct nerve impulses within the nervous system
What does the axons comprise of?
- Axon hillock: Tapers away from the soma to form the initial segment of the axon
- Axon proper: Axon can branch to form axon collaterals (and recurrent collaterals)
- Axon terminal: Site at which the axon comes into contact with other neurons at a synapse
Describe glial cells
- Glial cells are able to myelinated axons:
- Myelin is a membrane sheath that wraps around and insulates axons
- Gaps in the myelin sheath are nodes of ranvier: highly enriched in voltage gated Na+ ion channels
What are dendrites?
- Highly specialised neuronal projections that receive synaptic inputs from other neurons
- Dendrites of a single neuron are collectively termed a dendritic tree
Describe the structure of a dendrite
- Dendrites of some neurons are covered with specialised structures termed “dendritic spines”
- Small sacs of membrane that protrude from the dendrites of some cells to receive synaptic input
- Dendritic spine structure is sensitive to type and amount of synaptic activity
What is the problem with the dendritic spines?
A number of conditions have been associated with abnormal dendritic spine numbers (Alzheimer’s disease, schizophrenia)
Define the term neurotransmission
The fundamental process that drives information transfer between neurons and their targets
What is the 2 classification classes of neurons?
Neurons can be classified based on Neuronal structure and gene expressions
Describe what features of the neuron can be used in its classification (Neuronal structure)
- Number of projections
- Dendrites
- Connections: Sensory, motor or interneurons
- Axon length: Golgi type 1 and type 2
Describe how the neuron can be classified based on gene expression
- Can be classified based on the neurotransmitters they use
- These differences arise due to differential expression of proteins involved in neurotransmitter synthesis, storage and release
- Such as: Acetylcholine, GABA, Glutamate, Dopamine, Serotonin, Noradrenaline
