2.8 Glial Cells Flashcards
What are glial cells
Non neuronal cells in the nervous system that provide support, protection and maintenance for the neurons
What are the glial cells in the peripheral nervous system
schwann cells and satelite cells
What are the glial cells in the central nervous system
macroglial cells (oligodendrocytes, astrocytes and ependymal cells) + microglia
Describe how microglia are differentiated
mesoderm > mesenchymal cell > microglial cell
Describe how astrocytes are differentiated
ectoderm > neural tube > neuroepithelium > glioblast > astroblast > astrocyte
Describe how oligodendrocytes are differentiated
ectoderm > neural tube > neuroepithelium > glioblast > oligodendroblast > oligodendrocyte
Describe how ependyma are differentiated
ectoderm > neural tube > neuroepithelium > ependyma
Describe how schwann cells are differentiated
ectoderm > neural crest cells > schwann cells
Describe how satelite cells are differentiated
ectoderm > neural crest cells > satelite cells
What is the one glial cell that originates from the mesoderm instead of the ectoderm
Microglia
What are satelite cells
Satellite cells are small, flattened cells surrounding outer surface of cell bodies. They are found in sensory, parasympathetic and sympathetic ganglia.
How do satelite cells support PNS neurons
- regulate the micro-environment within the ganglia
- act as a protective barrier to viruses such as herpes simplex
- are sensitive to neurotransmitters and hormones
- respond to neural injury and inflammation
-contribute to neuropathic chronic pain by sensitising sensory neurons in dorsal root ganglia (hyperalgesia is when there is increased sensitivity to this pain)
What are the 2 glial cells that synthesise myelin (a lipid sheath)
schwann cells (PNS)
oligodendrocytes (CNS)
Which types of matter are myelinated axons present in in the brain
both grey and white matter
What is the glial cell effect of multiple sclerosis
Degeneration of oligodendrocytes leads to demyelination, reducing axonal conduction speed and impairing function
Give 2 differences between schwann cells and oligodendrocytes
One oligodendrocyte can myelinate multiple internodes (up to 50) on an axon and myelinate many different axons, but one schwann cell can onlu myelinate one internode
The oligodendrocyte produced myelin sheath is thinner than the schwann produced myelin sheath
Describe astrocytes
Astrocytes make up 20-50% of the brain and are either fibrous type (in white matter) or protoplasmic type (in grey matter)
How do astrocytes support CNS neurons
- Astrocytes are involved in synaptic activity, they regulate the K+ conc in the extracellular environment, they also regulate the synaptic conc of glutamate
- Astrocytes also provide metabolic support by taking up glucose from blood to produce lactate, the lactate is then used by the neuron to make ATP (in the lactate shuffle)
- Astrocytes support the brain blood barrier by allowing for tight junction maintenance between the endothelial cells of the barrier
- Astrocytes allow for neurovascular coupling (matching neural activity with blood flow, e.g higher activity needs more blood flow), astrocytes mediate the signalling between neurons and brain capillaries
- Astrocytes express glial fibrillary protein (GFAP) which allows astrocytes to become reactive in response to CNS injury or disease (processes undergo hypertrophy and GFAP expression increases)
Describe microglial cells
Microglia are highly motile ‘immune cells’ of the CNS that respond to nervous system injury and infection. They are perivascular cells that are either in a resting or active stae, microglia can be perineuronal or parenchymal.
How do microglial cells support CNS neurons
-microglia monitor activity in neurons and prune synaptic connections
-in a healthy or diseased brain, microglia can have many different functional states; e.g neuromodulatory, pruning, surveillant, systemic sensing, proliferating and phagocytic
-microglia interact with other cells by releasing and responding to different factors, this allows them to rapidly respond to injury or disease
Describe ependymal cells
Ependyma is made of ependymocytes and lines the ventricles of the brain and central canal of the spinal cord. It is ciliated simple columnar epithelium, the cilia aid the movement of the cerebrospinal fluid (CSF)
What is the choroid plexus
The choroid plexus is a network of modified ependymal cells and capillaries that lines all 4 brain ventricles and produces CSF. These cells are not cilliated but they form folds of microvilli. They also act as a barrier between the blood and CSF.
