CNS Cells + Synaptic Transmission Flashcards
What does white matter make up?
- Tract = bundles of myelinated axons connecting axons
- Fascicles
- Cortical medulla
- Internal capsule - contains many tracts
- Corpus callosum
What does grey matter make up?
Nucleus = cluster of cell bodies + their dendrites where synapses are made + information processed
How many layers does the cortex have?
6
What are the layers of the cortex interconnected by?
Association fibres (same side) Commissural fibres (opposite sides)
Name the types of neurological cells
- Oligodendrocytes - myelination
- Astrocytes
- Microglia - defence
- Ependyma - line ventricular system
What is the function of oligodendrocytes?
- Myelination in CNS
- Determine myelin sheath thickness + establishment NOR
What can cause deterioration of the myelin sheath?
Age
Multiple sclerosis
What is the glial syncytium?
Interconnects between glial cells
e.g. Astrocyte processes coupled by gap junction with pores that allow diffusion of second messengers, nucleotides + ions
What are the functions of astrocytes?
- BBB - regulate local blood flow
- EC [K+] levels ~ 2-2.5 mM
- EC glutamate levels ~ 3mM
- Regulate [Ca2+], [Cl-]. H2O in EC space
- Metabolic support for neurones - converts glucose > lactate
- Development of CNS
- Disease/pathology - astrocytomas, astrogliosis, epilepsy
- Control of breathing
How do astrocytes regulate EC K levels?
- Directly take up K from EC space by K pumps
2. Redistribute K within glial syncytium for discharge into EC space
How do astrocytes play a direct role in control of breathing?
- Astrocytes in chemosensory areas of brainstem = v. sensitive to pH
- Release ATP to stimulate chemosensitive neurones that cause increase in breathing
What is the function of microglia?
- Immune system of brain
- Resting cells that become activated by brain injury
What is the function of ependyma?
- Ciliated cuboidal cells
- Line ventricular system of CNS
- Modified ependymal cells in choroid plexus produce CSF
- Can develop ependymomas
What is a tripartite synapse composed of?
- 1 presynaptic
- 2 astrocyte processes
- 1 postsynaptic
What is the major excitatory NT in CNS?
Glutamate
