Neurones Flashcards
How do neurones communicate?
Via synapses
How many types of synapses are there?
2
What are the two types of synapses?
Chemical
Electrical
How do neurones communicate by a chemical synapse?
Via neurotransmitters
How do neurones communicate by a electrical synapse?
Via direct flow of ions
Which type of synapse happens more frequently?
Chemical
What happens during a chemical synaptic
- Axon potential depolarises synaptic terminal membrane
- Opening of voltage-gated calcium channels leads to calcium influx
- Calcium influx triggers neurotransmitter release
What is neural plasticity?
Changes in neuronal/synaptic structure and function in response to neural activity
What do neurons differ in?
Size
Morphology
Neurotransmitter content
Electrical properties
What are oligodendrocytes?
Myelinating cells of the CNS
What are oligodendrocytes unique to?
Vertebraes
What is the main function of myelin?
Insulates axon segments, enabling rapid nerve conduction
What are myelin sheath segments interrupted by?
Nodes of Ranvier – where ion channels are concentration, this allows saltatory conduction
What are oligodendrocytes important for?
They provide metabolic support for axons
What are microglia?
Resident immune cells of the CNS
Where do microglia originate from?
Originate from yolk sac progenitors that migrate into CNS during embryonic development
Describe microglia in ‘resting state’
Highly ramified
What are the functions of microglia?
Immune surveillance
Phagocytosis – debris/microbes
Synaptic plasticity – pruning of spines
“Good” (M2) & “bad” (M1) microglia
What are the most numerous glial cells in the CNS?
Astrocytes
What are the functions of astrocytes?
Structural - define brain micro-architecture
Envelope synapses
Metabolic support
Neurovascular coupling – changes in cerebral blood flow in response to neural activity
Proliferate in disease = gliosis or astrocytosis
What are the types of specialised astrocytes?
Radial glia
Bergmann glia
Muller cells
What are radial glia important for?
Brain development
Where are bergmann glia located?
Cerebellum
Where are muller cells located?
Retina
What is motor neurone disease?
Adult onset neurodegenerative disease characterised by loss of upper (motor cortex) and lower (spinal cord) motor neurones
What is multiple sclerosis?
Autoimmune demyelinating disease where immune cells attack the myelin sheath of oligodendrocytes
What are axons in the CNS gathered into?
Tracts
What is grey matter abundant in?
Abundant in neural cell bodies & processes
What does white matter contain?
Contains abundance of myelinated tracts & commissures
What are axons in the PNS bundles into?
Nerves
What is the blood-brain barrier formed by?
Endothelial cell tight junctions
Basement membrane (few fenestrations)
Astrocyte end feet
Pericytes (contractile, aid blood flow)
What is the blood-brain barrier sensitive to?
Inflammation
Hypertension
Trauma
Ischaemia
What are the functions of ependymal cells?
CSF production
Flow & absorption
What do ependymal cells allow?
Allow solute exchange between nervous tissue & CSF
What is the choroid plexus?
Frond-like projections in ventricles
What is the choroid plexus formed from?
Modified ependymal cells - villi form around network of capillaries
→ highly vascularised with a large surface area
What is the choroid plexus the main site for?
CSF production by plasma filtration driven by solute secretion
