Structure of the Nervous System Flashcards
By what characteristics can we group neurons?
Shape Electrical Activity Gene Expression Profile Neurotransmitter Connectivity
What processes do synaptic number and strength underlie?
Processing sensory information
Motor circuits
Memory formation
Synaptic plasticity
What are the components of the tripartite synapse?
Presynaptic terminal nerve
Post synaptic spine
Glial cell
What are the various roles of glia in the synapse?
Regulate neurotransmitter recycling
Releasing gliotransmitters
Ensheath synapses
Altering synapse number (microglia pruning)
What is the function and location of Satellite Cells?
PNS
Surround cell bodies in ganglia
Regulate O2, CO2, nutrients and neurotransmitter levels around neuron
What is the function and location of Schwann Cells?
PNS
Surround axons in PNS
Responsible for myelination of peripheral neurons
What is the function and location of Oligodendrocytes?
CNS
Myelinate CNS axons
Provide structural framework
What is the function and location of Microglia?
CNS
Remove all cell debris, wastes and pathogens by phagocytosis
What is the function and location of Astrocytes?
CNS
Maintain BBB
Provide structural support]
Regulate ion, nutrient and dissolved gas concentrations
What is the function and location of Ependymal Cells?
CNS
Line brain ventricles and spinal cord central canal
Assist in producing, circulating and monitoring of CSF
What are the three main stages of neurodevelopment?
Reading the instructions - genome level control
Identifying the components - differentiation and specification of neurons
Connecting the pieces - formation of neural circuits by axon guidance and neuronal migration
What are the three layers of the neural plate? What do they ultimately become?
Endoderm - becomes viscera
Mesoderm - becomes skeleton and muscle
Exoderm - becomes nervous system and skin
Describe the stages of neural tube formation.
- Neural plate forms a furrow at medial hinge point
- Creates neural folds and neural groove
- Epithelium delaminate - neural folds contact and fuse to become neural tube
- Cell differentiation produce neural crest cells that lie lateral to neural tube
- Entire CNS develops from neural tube
- Entire PNS develops from neural crest
Describe the outcomes of neural crest migration.
- Neural crest develops closely with mesoderm
- Mesoderm forms bulges either side of neural tube called somites (where spinal column and skeletal muscle develop from)
- NC cells migrate to form various structures - PNS (e.g. dorsal root ganglia), melanocytes, chondrocytes and smooth muscle
What is the name of the physical segments of the brain stem?
Rhombomeres
Which gene determines the specification of the anteroposterior axis?
Hox gene expression
Which morphogen determines the specification of the dorsoventral axis?
Sonic hedgehog
Where is Shh secreted from?
The notochord
What does low Shh induce?
Dorsal interneurons
What does high Shh induce?
Ventral motor neurons
What structure is responsible for axon guidance?
Growth cone
What are the two behaviours that rely upon midline crossing?
Locomotion
Coordination of sensory information
What process do Robo and Slit control?
Midline crossing
What ligand binds to Robo? Is it a positive or negative guidance cue?
Slit - chemorepellant
What would be observed in a Robo mutant?
Repeated crossing of the midline
Insensitive to Slit
What would be observed in a Slit mutant?
Axons collapse to midline - only respond to attractive signals, no repulsion keeping them away
Which direction do axons expressing high Robo grow?
Longitudinally - repelled by Slit
Which direction do axons expressing low Robo grow?
Attracted to and cross midline
What happens after axons cross the midline?
Upregulate Robo and remain on contralateral side
What process do Neuropilin and Semaphorin control?
Peripheral axon projection
What is repelled by the Semaphorin ligand?
Dorsal root ganglia
What ligands bind NRP1 and NRP2?
NRP1 - SEMA 3A
NRP2 - SEMA 3F
What is expressed in complementary gradients in the retina and tectum?
What is this an example of?
EPh receptors and ephrin ligands
Topographic mapping in the nervous system
Where are axons from the temporal retina directed?
Anterior tectum
Where are axons from the nasal retinal directed?
Posterior tectum
What are the advantages and disadvantages of phase contrast microscopy?
Adv - requires low illumination, no labelling, cheap
Dis - unable to automate image analysis, can only distinguish between high contrast structures
What are the advantages and disadvantages of fluorescent wide field microscopy?
Adv - better discrimination and temporal resolution than phase contrast
Dis - requires high illumination, limited depth of information
What are the advantages and disadvantages of confocal fluorescent microscopy?
Adv - 3D image, higher discrimination than wide field, allows image analysis, can be done in living cell
Dis - expensive, high illumination and long acquisition time
Why are mouse models used in neuroscience research?
Their cortex forms similar layers to ours - allows translation of findings related to higher brain function
Why are frogs used in neuroscience research?
Useful for studying neurodevelopment - easy to visualise brain stem and early projections
Why are flies used in neuroscience research?
Many common neurotransmitters with humans
Used to model human diseases
Why are chick embryos used in neuroscience research?
Doesn’t require a license - considered ethical
Minimal husbandry costs
Good model for early neurodevelopment - highly conserved
Good model for visual system - large eyes
