Neurons And Glia Flashcards
Granular vs agranular cortex
Graunlar- primary sensory areas (IV)
A granular- v1, frontal cortex, EC (no IV)
Pathway from whiskers to barrel cortex in mouse
Whiskers
Trigeminal nerve
Brainstem
Spinal/principal trig nerve
Thalamus
Posterior medial/ ventral posterior
Barrel cortex
Layers of cortex
1- inhibitory neurons (from thalamus)
2- pyramidal cells
3- pyramidal cells- exciaitory project to other areas
4- Stellate cells
5- excitatory project to other subcortical area. Synapse with later 1
6- project to thalamus and other areas
Trisynaptic pathway
Ec-dg- hippocampus - ca3 - ca1- hippocampus
Characteristics of excitatory neurons
Glu
Pyramidal cells in layers 3+5 of cortex
Some found in layers 2/6 pyramidal or stellate cells
Project to other cortical columns and subcortical nuclei
Characteristics of inhibitory neurons
Gaba
All cortical areas
Usually local circuit but some long-range gabergic projections
Origins of inhibitory interneurons
Medial ganglionic eminence
Caudal ganglionic eminence
What are the post synaptic targets of interneurons
Perisomas- synapse with soma or axon of pyramidal cells
Dendrites- synapse with basal or distal dendrites of pyramidal
Interneurons- inhibit other interneurons
Function of perisomes
Control whether pyramidal cell fires
Dendrite function
Control which inputs are activated
Interneurons function
Mediate disinhibition of excitatory input neurons
Markers of interneurons subtype
Pv- basket, fast spiking perisomatic, axo-axonic, chandelier
Sst- olm, martinotti
Sht/vip- other interneurons
How are pyramidal cells heterogeneous
Don’t fockin know
Different morphologies (pyramidal)
What are pv cells
Fast spiking interneurons - generating Rythmic activity and inhibit pyramidal cells
Sst function
Selecting inputs to pyramidal and vip (vasoactive intestinal peptide) neurons
What are neuroglia cells
Not electrically excitable non-neuronal cells of nervous system that unify the reticular and neuronal theories of brain organisation (supporting cells or nervous system)
What glia are part of cns
Astrocytes
Oligodendrocytes
What glia are pns
Schwann
Satellite
Enteric glial cells
What are ng2 cells
Cns projector cells of oligods
Functions of astrocytes
Aids In formation of blood brain barrier
Cns tissue fluid composition regulation and metabolic support of neurons
Structural support and organisation of cns
Repair processes replace damaged neurons
Assist with neuronal development
Function of oligods
Myelinate cns Axons
Target of autoimmune attack
Has specific myelin proteins (plp, dm20,mbp)
Function of microglia
Synaptic modification
Phagocytose weak synapses after injury or during development
Immune cell of brain
Mediate synaptic pruning
How do microglia contribute to synaptic plasticity
Release insulin-like growth factor 1 and BDNF.
How do microglia function in immunity
After tissue damage DAMPS are released which are neurotoxins
Also release inflammatory products e.g TGFb IKL6 IKL10
What are radial glia
Made before neurogenesis and guide neuronal migration. They become astricytes or dissapear after migration
Order of neuron/glia development
Neural stem cells- radial glia- neurogenesis (neurons)1 glial progenitor cells- astricytes and oligods
What are nIPCS
Differentiate into radial glia to contribute to neurogenesis. They take on characteristics of astrocytes e.g expression of glu transporters. Glycogen granules and intermediate fillanents
Origins of glial cells
Astrocytes and oligods and ependymal - ectoderm
Microglia - mesoderm (from yolk sac development)
Main functions of glia
Surround neurons to hold them in place
Supply nutrients and oxygen to neurons
Insulate one neuron from another
Destroy or remove carcasses of dead neurons
How to glia effect synapses
Without glia there would be no synapses
Modulate LTP using d-serine
Functions of Astrocyte secretory factors
Tsp- silent synapses
Hevin (and sparc)- both are needed to make a synapse
Tgfbeta1 and d-serine- promotes excitatory synapses and some inhibitory
Astrocyte communication
Communicate via Ca waves
When cell stimulated longer there is more ca released into field
Astrocytes are able to propitiate cellular signals as waves of intracellular ca changes- speak from one Astrocyte to another
Ca waves influence activity of adjacent neurons and modulate synaptic transmission
After Astrocyte ca wave passes a neuron it responds with its own rise in ca
Role of d-serine
Co agonist for NMDAR
Release from astrocytes and binds to synaptic NMDAR containing glun1/2a subunit when prestnaptic neuron releases glu
What are tanycytes
Specialised , non ciliated emendymal cells (type of astroglia)
During perinatal period some radial glia can become tanycytes
Act as a selective barrier and Carrier
Involved in reproduction and metabolism
Location of tanycytes
Cvo of brain and Vasolateral walls of 3rd ventricle
And median eminence (cvo)
What is the median eminence
Circumventeucular organ controlling excess of blood borne molecules - forms the floor of the 3rd ventricle in hypothalamus
Allows for communication between neural tissue, periphery, blood and csf
What’s important about the fenestrated endothelium of the ME
Molecules like hormones and nutrients can enter the brain freely through it
Purpose of blood brain barrier
Protects brain from external agents in blood
How are tanycytes carriers?
They carry/ transport leptin into the csf because tanycytes in the ME have tight junctions which would stop them from passing freely
What is leptin
Hormone that acts within hypothalamus to suppress food intake and decrease body adiposity
It also alters/ improves cog functions by acting with other brain areas
Where can hormones be transported without tanycytes
Me-csf barrier made of b-tanycytes on the lateral side do not have tight junctions so hormones can pass freely. Also through fenestrations to teach ME
How is diffusion efficient in the ME
Csf moves due to ciliated ependyma that beat rythmicalky. Tanycytes don’t have cilia so move slowly which creates a gradient between csf and third ventricle
What are metabolites
Micro molecules for cellular functions like energy stimulation
How do tanycytes sense glucose
Tanycytes have glu 1 and 2 receptors and all machenry to perform glycolysis to sense variation of glucose in csf
What happens when tanycytes detect glucose
Increase in intra ca and ATP and lactate
This activates nearby neurons to regulate feeding behaviour
Why is it important that tanycytes respond to lactate
Breakdown of glucose into lactate . Some neurons involved in feeing behaviour can’t process glucose directly so rely on tanycytes to change info into ATP or lactate
Hpg axis
Gnrh neurons in hypothalamus-
Medial eminence (release gnrh)-
Stim gonadotropin In a.pituitary-
Lh and fsh release-
Follicular maturation in ovary-
Secrete estridiol
Sema7a function
Secreted by tanycytes and regulates morphological plasticity of the ME of adult females
Blocks gnrh neuron to pericapillary space by allowing tabycytes to grow end feet
Proestrous stage and sema7
The end feet retract so gnrh terminals can reach pericapillary space .
Estrogen during proestrous stage promotes sema7 release from fenestrated epithelium of ME
Sema7 during diestrus stage
High oestrogen levels cause Sema7 acts directly on gnrh terminals to induce retraction of end feet from pc space and promote growth of gnrh neuroendocrine axons towards pc space
At this stage low oestrogen promotes sema7 by tanycytes which causes growth of end feet
Hpt axis
Trh found in paraventrucular nucleus of hypothalamus -
Project to ME-
Release trh
Thyroid cells in a.pituitary cause Tsh secretion-
Thyroid produce T4
Negative feedback
Role of dio2
Make inactive T4 into active T3
Most expression in astrocytes and tabycytes
How is tanycyte end feet modulated in ME
Tanycytes are activated by TRH via gaq pathway
