Neurons Flashcards
Neurones
Receive inputs via dendrites, send signals out from axon hillock along axons. Mainly formed during embryonic development.
What colours do H&E stain?
Haemotoxylin = nucleic acids blue
Eosin = proteins red
Types of synapses
Chemical (via neurotransmitters eg. glutamate, GABA, dopamine, serotonin)
Electrical via direct flow of ions. They enable synchronised electrical activity eg brainstem and hypothalamus
Chemical synaptic transmission basics
Axon potential depolarises synaptic terminal membrane.
Opening of voltage gated calcium channels lead to calcium influx
Calcium influx triggers neurotransmitter release
http://www.neuroscientificallychallenged.com/blog/2-minute-neuroscience-synaptic-transmission
Where are excitatory synapses often concentrated?
On the dendritic spines. (Also contains ER so proteins can be made quickly in response to certain signals.)
Spines and neural plasticity
Changes in neuronal / synaptic structure and function in response to neural activity. Basis of learning and memory.
Spine remodelling linked to neural activity.
Decreased spine density in Alzheimer’s and schizophrenia.
Betz cells
Upper motor neurons with long projections, vulnerable in MND.
Oligodendrocytes
Myelinating cells of CNS.
Wraps its processes (membranes) around axons many times, v compacted and lipid rich and some proteins.
Video about myelin specific proteins used as ‘markers’
http://www.neuroscientificallychallenged.com/blog/2-minute-neuroscience-myelin
One oligodendrocyte can myelinate many segments of different axons.
Provide metabolic support to neurons.
Myelin insulates axon segments enabling rapid nerve conduction via nodes of Ranvier.
Microglia
Immune cells of CNS
Originate from yolk sac progenitors that migrate into CNS
In resting state, are highly ramified
When activated, more amoeboid shape and remove debris/pathogens
Proliferate (multiply) at sites of injury
Phagocytosis
Synaptic plasticity - pruning of spines.
Can have both good and bad microglia - can be overactivated and cause damage.
Activated by cytokines.
Astrocytes
“star-like cells” (not all are star-shaped though!)
Most numerous glial cell
Common “marker” glial fibrillary acidic protein (GFAP)
Contribute to blood-brain barrier.
Line blood vessels.
Have water channels (aquaporin 2)
Envelope synapses - can take up excess ions and neurotransmitters to prevent toxicity to neurons.
(Glutamate they take up can be converted to glutamine which is transported to neurons as store of carbon for energy.)
Neurovascular coupling - increased blood flow when increased neural activity. Dilate blood vessels to increase blood flow.
Astrocytosis (proliferation of astrocytes) in damaged tissue.
Specialised astrocytes
Radial glia (important for brian development)
Bergmann glia (in cerebellum, define architecture and structure)
Muller cells (in retina)
Abundance of neuronal cell bodies lie in
nuclei
Axons are gathered into
tracts
Tracts that cross midline are
commissures
In PNS ,cell bodies and supporting cells located in
ganglia
