Cells of the CNS Flashcards
What is the broad function of glial cells?
Support neurons
List 5 types of glial cells?
Astrocytes Oligodendrocytes Schwann cells Ependymal cells Satellite cells of ganglia
What are microglia?
Immune cells
What are macroglia?
Refers to glial cells
How many layers are there in the cerebral cortex?
6
What lies in the six layers of the cerebral cortex?
Cell bodies of neurons and glia
What is the function of the ventricular system?
Formation and passage of CSF
What is the choroid plexus?
Vascular structure arising from wall of each ventricle
What is the function of the choroid plexus?
Forms CSF
Describe the structure of ependymal cells?
Columnar or cuboidal cells
Sometimes ciliated
Non basal laminar (different to epithelial cells)
Where are ependymal cells found?
Lining central canal of spinal cord and ventricles
Why are ependymal cells sometimes ciliated?
Aid CSF flow
Why are neurons highly synthetic?
High level of protein synthesis, for structures such as ion channels, receptors and cytoskeleton
Describe the metabolic characteristics of neurons?
Metabolically limited
Are neurons capable of turning over?
Most are terminally differentiated
What are the three components of the cytoskeleton of neurons?
Actin
Intermediate filaments
Microtubules
What is the role of actin in neurons?
Shape changes allowed by rapid assembly/disassembly of actin
What is the role of microtubules in neurons?
Axon transport
What are microtubules composed of in neurons?
Tubulin
Describe the volume distribution of neurons?
What is the consequence of this?
High proportion is axon and dendrites
So, random damage often involves axon (prone to damage due to length)
What are Nissl bodies?
Large granular body in neurons
Contains RER and free ribosomes
How can the high level of protein synthesis in neurons be demonstrated in cytology?
Presence of Nissl bodies
How is protein supplied to the distal extremities of neurons?
Axonal transport
What are glial cells sometimes called?
Macroglia
What is the most important glial cell type in the brain?
Astrocytes
List the passive support functions of astrocytes?
NT uptake and degradation K homeostasis Neuronal energy supply BBB maintenance Injury response and recovery
List the active functions of astrocytes?
Modulation of neuronal function
Modulation of blood flow
Which particular NTs do astrocytes uptake and degrade?
Glutamate and GABA
Describe how astrocytes are involved in K homeostasis/
K released when neuron depolarises
Glial cells suck up excess
Is glutamate excitatory or inhibitory?
Excitatory
Is GABA excitatory or inhibitory?
Inhibitory
What are the most important NTs in the brain?
Glutamate and GABA
What do astrocytes express transporters for?
Glutamate and GABA transporters
For reuptake
What happens if glutamate transporters are blocked from working? Why?
Massive increase in depolarisation
Neuron is also depolarised for longer period of time
(Because more glutamate remains in synapse for longer)
Why are glutamate transporters on glial cells so important?
Removal of glutamate is crucial for maintaining normal function and integrity
If glutamate remains in the synapse, it will continually stimulate the neuron,. which can lead to cell death
By what mechanism do glial cells communicate with each other?
Ca waves
Synaptic vesicles - exocytosis
What can initiate Ca waves in glial cells?
NTs
Trauma
Spontaneous
Inflammatory mediators
How/why are glial cells excitable?
Mechanisms that involve Ca
To what extent do glial cells contain and release synaptic vessels/
Very small number
How are neurons inhibited?
Ca wave
What is the mechanism of neuron inhibition involving glial cells? How are glial cells able to act in this way?
ATP release from glial cells > Ca wave > hyperpolarisation
Glial cells are able to directly modulate the function of neurons in their vicinity
How can glial cells regulate neuronal function?
Can directly modulate neurons in their vicinity by release of ATP > Ca wave > hyperpolarisation
How can glial cells regulate vasculature?
Can regulate vascular tone via initiation of Ca wave > vasoconstriction or vasodilation
(BV constricts as Ca wave moves closer)
How do astrocytes know when to regulate vascular tone?
Astrocyte can sense what is going on at synapse, and alters blood flow in accordance with level of activity and energy requirements
Which cell types are involved in myelination?
Oligodendrocytes
Schwann cells
What is the predominate cell type of white matter?
Oligodendrocytes
What is the role of oligodendrocytes?
Myelinate axons in CNS
What is the role of Schwann cells?
Myelinate axons in PNS
What are the differences between oligodendrocytes and Schwann cells?
- Oligodendrocytes - CNS; Schwann cell - PNS
2. Oligodendrocytes extend processes that wrap around several axons; Schwann cells wrap around a single axon
What are the immune cells of the CNS called?
Microglia
Where do microglia arise from?
Bone marrow
What immune cell type do microglia resemble?
Macrophages, as they are phagocytic
Describe the action of microglia?
Local defence cells
Constantly survey the CNS by extending processes
Are phagocytic
When do microglia change?
Change in response to inflammation or injury
How do microglia change in response to inflammation or injury?
Upregulate cytokines and growth factors
Describe the broad structure of peripheral nerves?
Each nerve fibre surrounded by endoneurium
Bundles of nerve fibres form fascicles
Each fasicle surrounded by perineurium
Bundles of fasicles surrounded by epineurium
What does endoneurium enclose?
A nerve fibre and Schwann cell
What does epineurium enclose?
Bundles of fascicles
What does perineurium enclose?
A fasicle
What are ganglia?
Aggregations of neuron cell bodies that lie outside the CNS
What are the two types of ganglia?
Sensory and autonomic
What do sensory ganglia contain?
Cell bodies of sensory neurons
What do autonomic ganglia contain?
Cell bodies of post-ganglionic neurons
Where are the cell bodies of post-ganglionic autonomic neurons found?
In autonomic ganglia
