neurons Flashcards
3 types of CNS cells
- ) neurons
- ) Glia
- ) Others
Features of neurons
- Have dendrites/cell body/axon/axon terminals
- Axon terminals communicate with other axons
- Communicate electrically via synapses
Histology
- Large neurons: speckly pattern: missel body
- H&E: stains nucleic acids blue and proteins red
What is LFB
LFB (luxol fast blue): stains myelin
What is CV
Stains Nissl (RER)
Types of neurons
- ) chemical
2. ) electrical
Features of electrical synapses
- Have connexons and connecins
Features of chemical synapses
- Rich in mitochondria
-
How does synaptic transmission take place?
- Influx of calcium allows neurotransmitters to be released/fused on the membrane
Dendritic spines
- Synapses are concentrated here
Synaptic plasticity
- They are dynamic structures
- Neural plasticity: basis of learning and memory
- Spinal remodelling linked to neural activity
Features of neuronal heterogeneity
Heterogenous for::
- ) size
- ) morphology
- ) neurotransmitters
Features of upper motor neurons
- Large
- Excitatory
- Glutamatergic
- Long projection pyramidal cells
- Use GABA
Oligodendrocyte features
- Myelinating cells of CNS
- Myelin insulates axons segments + enables rapid nerve conduction
- Provides metabolic support for axons]- Myelin sheath segments interrupted for nodes of ranvier
Oligodendrocyte features
- Myelinating cells of CNS
- Myelin insulates axons segments + enables rapid nerve conduction
- Provides metabolic support for axons]- Myelin sheath segments interrupted for nodes of ranvier]
- can myelinate multiple axons
Myelin sheath features
- Multiple layers of membrane
- 70% lipid and 30% protein
- Myelin specific proteins e.g. MBP involved in compaction
Mircoglia features
- Immune cells of CNS
- Originate from yolk sac projenitors
- In ‘rest’ they are highly ramified/motile processes (2-3 mm/min_
- In activation: retract processes and become more rounded
- proliferate at sites of injury (phagocytic)
Functions of microglia
- ) Immune surveillance
- ) Phagocytosis
- ) Synaptic plasticity: pruning
Astrocyte features
- most numerous of the glial cells
- Highly heterogenous
- Common maker is GFAP
Astrocyte morphologies
1.) Fibrous: white matter/contact blood vessels/pia/nodes od ranvier
Astrocyte functions
- developmental: radial glia
- structure: define brain micro-architecture
- envelope synapses: tripartite synapse
- homeostatic: buffer K+
- Metabolic support
Specialised astrocytes
1.) rADIA
Specialised astrocytes
- ) Radial glia: in brain development
- ) Bergmann glia (cerebellum)
- ) Muller cells (retina)
MND spinal cord shows pathological changes in
Motor neurons/microglia/astrocytes
What does pathological CNS lesions in MS involve
Oligodendrocytes/neurons/T lymphocytes
What does acute symptoms in MS reflect dysfunction in
neurons
CNS terminology
- Abundance of neuronal cell bodies in nuclei
- Axons gathered into tracts
- Tracts that cross midline = commissures
- Grey matter abundant in neural cell bodies & processes – neuropil contains few cell bodies
White matter contains abundance of myelinated tracts & commissures
PNS terminology
Cell bodies & supporting cells located in ganglia – e.g. dorsal root ganglia (DRGs)
Axons bundled into nerves
Many PNS axons are enveloped by Schwann cells (myelinating cellsof the PNS – neural crestderived)
Blood brain barrier
- blue dyes in blood won’t penetrate brain tissue
How is the blood brain barrier formed?
Formed by endothelial cells/astrocytes and pericytes
Features of the blood brain barrier
- Endothelial tight junctions
- Astrocyte end feet
- Pericytes
- Continuous basement membranes: lacks fenestrations
- Need specific transporters for glucose/water
What do circumventricular organs lack
Normal BBB: sensory and endocrine functions
What are these circumventricular organs
- ) Subfornical organ
- ) Pineal body
- ) Area Postrema
- ) Posterior Pituitary
- ) Organum Vasculum of the Lamina terminalis
CSF drainage
- occurs via multiple roots
- perineural route via olfactory/brainstem/spinal nerves
Features of ependymal cells
- epithelial like
- line ventricles + central canal of spinal cord
- involved in CSF flow
- Ciliated to facilitate flow
- Allow solute exchange between vervous tissue and CSF
Features of the choroid plexus
- formed from modified ependymal cells: villi form around network of capillaries- large surface area
- Main site CSF production by plasma filtration
- GAP junctions between cells form blood-CSF barrier
- Projections in ventricles
