Cells And Models Flashcards
Name the four functional regions of a neuron
Input, integrative, conductive, output
Local interneurons often lack a conductive component
Outline the input region of a neurone
Electrical signal, integral to the cell
Outline the integrative region of a neuron
Electrical signal, integral to the cell
Outline the conductive region of a neuron
Electrical signal, integral to the cell
Outline the output region of a neuron
Chemical signal, where the chemical substance is ejected by the cell into the synaptic cleft
How are neurons classified
Neurones can be classified as unipolar, bipolar or multipolar based on the number of processes that originate from the cell body
Based on:
Morphology
Major functions
Physiology
Neurotransmitter
Gene expression profile
Location
What glial cells are found in the peripheral nervous system
Satellite cells and Schwann cells
What glial cells are found in the central nervous system
Oligodendrocytes, astrocytes, microglia and ependymal cells
Outline astrocytes
-star-shaped glia
-long, thin processes that enfold all the blood vessels of the brain and ensheath groups of synapses
What key roles do astrocytes have
-nourishing neurones
-blood-brain-barrier -> take up glucose from the circulation and deliver energy substrates to neurones
-regulate extra-cellular concentrations of ions, neurotransmitters and other molecules
-modulating synaptic signalling
-development of synapses, release of neurotrophic and gliotrophic
Outline the blood-brain barrier
-a key structure protecting the brain from systemic insults
-tightly regulates the movement of ions, molecules and cells between the blood and the brain, essential for neuronal homeostasis and protects the brain tissue from toxins and pathogens
What is the blood-brain barrier formed by
-endothelial cells which are interconnected by very complex interendothelial tight junctions
-pericytes, smooth muscle-like cells
-astrocytes projections surround pericytes= endfeet
What is a tri-partite synapse
Using high-affinity transport channels, they rapidly uptake released neurotransmitters , converted and end-product is transferred back to neurones
High conc of extra cellular neurotransmitters can lead to excitoxity, and death of neurones
Astrocytes can also release gliotransmitters to modulate synaptic signalling
Outline the two myelinating glial cells
Oligodendrocytes in the CNS-produces for as many as 30 axons
Schwann cells in the PNS- produces for 1 axon
Allows for rapid conduction of electrical a signals along the axon, produces thin sheets of myelin that wrap concentrically, around segments of axons
Outline the nodes of ranvier
1um unmyelinated gaps, plasma membrane of axon is exposed to the extracellular space
-high density of Na+ channels
-increases the speed of conduction and prevent the action potential from decaying, allowing it to travel over long distances
Outline microglia
Migrates from bone marrow to nervous system
Able to change morphology depending on the physiological pathological context
Rapid activation in response to environmental changes in the CNS
Processing and presenting antigens to lymphocytes and secreting cytokines during inflammation
Can become macrophages and clear debris in the CNS Processing
Can regulate synaptic pruning
What are ependymal cells
Line the ventricles in the brain
Single layer of ciliates cuboidal cells
Helps move cerebrospinal fluid through the ventricular system
Outline satellite glial cells
Wrap around neuronal cell bodies
Found in the peripheral ganglia
Control neuronal homeostasis
Express K+ channels and glutamate transporters around synapses
What are model organisms
A specie that has been widely studied, usually because it is easy to maintain and breed in a labatory setting and has particular experimental advantages
Helps her stand fundamental mechanisms applicable to more complex systems, including humans
Outline the advantages and disadvantages of using rodents as mammal models
Advantages
-complex behaviours
-organs homologous to humans
-genetic similarity to humans
Disadvantages:
-very expensive husbandry costs
-experimental cycle long
-ethical constraints
Outline the advantages and disadvantages of using zebra fish as non mammalian vertebrate
Advantages:
-high reproductive rate
-development is external
-genetic similarity to humans
-embryos and larvae are transparent
-possibility to study complex behaviours
Disadvantages:
-moderate predictivity
-moderate translation value
Outline the advantages and disadvantages of using drosophila as an inverterbrate model
Advantages:
-easy to work with
-short generation time
-low cost of maintanence
-small genome (4 chromosomes)
-study simple behaviours Disadvantages
-genetically distant from humans
-simple anatomy
-no adaptive immune system
Outline non-human primates as a model
Better position to provide relevant translational information because of their higher brain complexity and homologa to humans
Lack of resources and formal training, strict legislation and ethical issues impede broa access to larger animals
Outline the 3Rs of ethical considerations
Replacement- methods which avoid or replace the use of animals
Reduction- methods which minimise the number of animals used per experiment
Refinement- methods which minimise suffering and improve animal welfare
Outline in vitro models
Can differ in terms of dimensions, scaffolding, biomaterials
2D cell cultures
Spheroids
Organoids
Scaffold-based cell culture
Organ-on-a-chip
Are all models wrong?
Yes, they’re useful but always wrong as there’s no perfect models for humans except for humans themselves which has ethical implications
