Neurons and Astrocytes Flashcards
Describe how neurons are adapted to their function according to their location in the CNS Appreciate the diversity of neuronal subtypes through their cellular structure Describe the varied function of astrocytes Discuss the cell-cell interactions of astrocytes with other CNS cells Relate the biology of neurons and astrocytes to nervous system physiology and pathology
What determines whether a neuron is peripheral or central?
Location of their cell body - peripheral neurons have their cell bodies outside of the CNS, whereas central neurons have their cell bodies within the CNS
Name a class of peripheral neurons which extends into the CNS
Dorsal root ganglion sensory neurons
Describe the contents of a neuronal cell body
A neuronal cell body contains a large nucleus, prominent nucleolus, abundant rough ER, well-developed Golgi apparatus, abundant mitochondria, and a highly organised cytoskeleton
Describe four types of neuron morphology
Unipolar, bipolar, pseudounipolar, and multipolar
What is the most common neuron morphology?
Multipolar
Name two types of bipolar neurons
Retinal neurons and olfactory neurons
Name two types of multipolar neurons and their location
Pyramidal neurons in the hippocampus and Purkinje cells in the cerebellum
What morphology do pain sensory neurons typically have?
Unipolar
Name five organisational mechanosms for neuron circuits
Divergence, convergence, serial processing, parallel processing, and reverberation
What are the three main neuronal compartments?
Dendrites, axons, and synapses
State the contents of the axon compartment
Axon hillock, myelin sheath, nodes of Ranvier, paranode, and juxtaparanode
Name specific components of the somatodendritic compartment
Microtubule stabilising protein MAP2B, all neurotransmitter receptors, postsynaptic density scaffolding, and signalling proteins for the post-synapse
What part of a neuron receives the majority of synapses?
Dendritic spines
Name four shapes dendritic spines can take
Stubby, thin, mushroom, filopodium
What is the function of tau in the axon?
It is a microtubule stabilising protein (MAP)
Name three components required at the pre-synapse
Neurotransmitters, growth factor receptors, and SNARE complexes
Name two forms of synaptic terminal
Boutons and varicosities
Name three places a neuron can synapse
With another neuron, a muscle cell, or a gland
How is vesicle fusion triggered at the synapse?
Depolarisation causes a calcium ion influx at the terminal, leading to vesicle fusion via molecular binding complexes
Are axo-somatic and axo-axonic synapses usually excitatory or inhibitory?
Inhibitory
Are axo-dendritic synapses usually excitatory or inhibitory?
Excitatory
Name two excitatory neurotransmitters
Glutamate and acetylcholine
Name two inhibitory neurotransmitters
GABA and dopamine
How many glutamate receptor proteins are there?
11
What percentage of brain cells is made up by astrocytes?
40%
Name three components of the cytoskeleton of astrocytes
Glial fibrillary acidic protein (GFAP), microtubules, actin
State a metabolic function of astrocytes
Cholesterol production, providing lactate to neurons, synthesis of apolipoprotein E
State how astrocytic dysfunction can impact on neurodegeneration
It can increase glutamate cytotoxicity, increase levels of calcium and ATP release, increase nitric oxide production, cause accumulation of superoxide dismutase, and form glial scars
How do astrocytes contribute to the blood brain barrier?
The blood brain barrier is formed by the tight association of brain capillary endothelial cells. Astrocytic endfeet enwrap endothelial cells, providing a gateway for nutrients to enter and metabolites to leave the CNS
Give 5 functions of astrocyte-expressed aquaporin 4
Potassium buffering, CSF circulation, interstitial fluid resorption, metabolic waste clearance, neuroinflammation, osmosensation, cell migration, calcium ion signalling, regulation of the volume of extracellular space
How can astrocytes modulate neuronal function at the synapse?
By removing and releasing neurotransmitters
How do astrocytes help to recycle GABA?
They endocytose unbound GABA, convert it to glutamate and then glutamine, and re-supply it to the neuron
Why do astrocytes act as a potassium reservoir?
For neurons to function, extracellular potassium concentration must be kept low
Astrocytes help to spatially buffer potassium via gap junctions. Which other cell type contributes to this process?
Oligodendrocytes
True or false: astrocytes are the only brain cells that store glycogen
True
Give two examples of radial glia
Bergmann glia in the cerebellum, and Muller cells in the retina
