Download Nolte – Chapter 1 (Introduction to the Nervous

Nolte – Chapter 1 (Introduction to the Nervous System) and all Class-Notes
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Neuronal Variations by Anatomy
o Multipolar
 Multiple dendritic projections from the cell body and almost
always an axon
 Pyramidal.
 Cerebellar purkinje
o Bipolar
 Two processes – one axon – one dendrite
 Retinal cells/ olfactory/ vestibular hearing.
o Unipolar
 Only one axon that emits from one cell body. Nothing else.
 An example of this would be sensory neurons with cell bodies
in the dorsal root ganglia.
 Usually developmental.
o PseduoUnipolar
 Cell body is pinched off and there are no dendrites.
 Carries axon potentials back from skin (backwards) to cell
body then sends again to the spinal cord
 Dorsal root ganglia
Neuronal Variations by Chemistry
o Cholinergic
 Use acytelcholine
 Preganglionic
 And postganglionic for parasympathetic as well
(postganglionic for sympathetic uses epinephrine –
adrenergic)
 Motor neurons
o Biogenic Amines
 Dopamine, serotonin, epi, histamine. Emotions.
o Amino Acids
 Gluatamate(+)
 Glycine and GABA (-)
 Found in flattened vesicles(artifact of the tissue)
 Primary for CNS.
o Peptidergic
 Largest class. Endorphins. Regulate food intake in
hypothalamus.
o 4th gen
 endocnabannoids, progesterone, NO
 regulated by synethsis (once synthesized, they are out)
 manufactures in enurons and glia.
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Interneurons
o All processes confined to a single, small area of the CNS
Projection Neurons
o Long axons connecting different areas, such as from cerebral cortex to
spinal cord.
Thalamo-Cortical Neurons
o Two Firing modes
 Burst mode
 During sleep and epilepsy
 Transfer mode
 Awake and alert
Nuclei
o A containment of cell bodies that are functionally related to one
another.
Cell Body
o Synthesis of all neuron’s enzymes, proteins
o Nucleuoli
 Transcription of RNA
o Ribosomes
 Stain intensely with Nissl substance
o Inclusions
 A number of things that are not organelles
 Melanin granules, lipfuscin (waste), pigments, lipid.
 Substantia nigra have a lot of melanin
 Inclusions can change the color (like the iron in the red
nucleus)
Microtubules
o Arrangement of protein around a hollow core.
 Use the protein tubulin
o Tau proteins help to stabilize microtubules
 When tau messes up, they make neurofibrilate tangles
(tauopathies)
o Neurofilaments
 Neruon’s version of the intermediate filaments found in most
cells. They are ropelike assemblies of strands of polymers.
o Serve as the substrate along which organelles are transported.
o Microfilaments anchor membrane molecules in place (receptor
molecules at synapses)
o Transport away from the soma is termed anterograde
 Kinesin moves things this way
o Transport towards the soma is termed retrograde.
 Dynein moves things this way.
o Transport can be slow or fast
o Tubulin
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A structurally polarized molecule that can be added only in one
orientation to one end of an existing microtubule.
 This is why we need two differen molecules to move
antero and retro.
Axon
o Hillock is the initial segment where the action potential is determined
to propogate or not.
 All incoming signal is essentially summed up here.
o The “apical” compartment of the polarized epithelium
o Only ever one axon.
o Contain mitochondria, vesicles, actin, microtubules, and filaments.
o The end is the terminal bouton(presynaptic)
 Filled with vesicles of neurotransmitters
 Clear vesicles: low molecular weight with transmitters
like glutamate and lysine
 Dense cores(electron opaque): higher moleculare
weight. Typically inhibitory.
Dendrite
o The basolateral (along with the cell body) compartment of the
polarized epithelium.
o Contain a lot of the same organelles as the cell body.
o Spines are filled with mitochondria and receive the input
 Spines are primarily concerned with excitation.
 Spine remodeling after learning.
o Much thicker than axons.
Schwann Cells
o Provide metabolic support and electrical insulation in the PNS.
o Some are flattened out as satellite cells.
o Provide an infrastructure/scaffolding for new growth
 Emit NGF
o Envelop unmylenated PNS axons
Myelination
o Myelin between two nodes of Ranvier is known as an internode.
o Less myelin, less conduction, more leakiness.
o PNS- Schwann CNS- Oligo
Glia
o Greek for Glue
o Literally form a matrix over the entire CNS
o “neuropil” fils the space between neurons and dendritic branches
(everything else).
o Macroglia
 Oligodentrocytes produce internodes on multiple
axons(upwards of 10)
 Astrocytes will sit inside these internodes at the nodes
of Ranvier.
 MS messes with oligo and prevents the upkeep of myelin.
o Astrocytes (known collectively as astroglia)
 Protoplasmic in gray
 Fibrous in white
 Radial glia is a third type during development.
 Found in dentate gyrus and subgranular zones.
 Give structural support to the CNS
 Regulate extracellular ionic concentrations and transfer
metabolites to and from neurons.
 Maintain balance and act as a sink for potassium and
can transmit them via tight junctions to other
astrocytes.
 Take up GABA, glutamate, ad glycine.
 Basically sit around synapses and inside nodes of
ranvier.
 Clearance of transmitters
o Take up glutamate with pumps and make it into
glutamine and put it back into the presynaptic
terminal.
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 Release energy substrates
 Reactive astrocytes respond to injury
 Make a scar.
 Contact blood vessels
 Glucose comes in from the blood and the astrocytes turn
that into lactate(energy substrate) to give energy to the
presynaptic neuron.
 Help form the BBB as well (alongside endothelial cells)
 Aquaporons in the end feet help with the BBB.
 Can dilate them with NO and PRE to increase CBV
o After a gluatminergic excitation.
 Synthesize neurosteroids (estrogen progesterone)
 Can release thrombosin to help create new synapses.
 Have receptors for glutamate that can cause calcium signaling
that in turns realeases more glutamate into the synapse to help
accelerate a posy synaptic response.
 Called “gliotransmitters”
o Also include D-serine, ATP, adenosine.
o Epnedymal
 Ventricle lining
 Some are specialized as a secretory epithelium that produces
CSF
 They are ciliated and help accelerate flow.
o Microglia
 Respond to injury
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o NG2
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Activated after damage. Increase in size during
response.
Motile in their search for damage and disease (on patrol)
Can transform into macrophages to feat on debris.
Derived from the same precursors of family that give rise to
blood cells.
 Bone marrow.
Originally populate the CNS during development.
 When needed to be replaced, they divide locally.
Take part in synaptic turnover and plasticity.
 C1q gets emitted by neurons during development and
remodeling. If the microglia detect this, they come in
and prune by physically chewing up the synapses.
o Astrocytes might start this process by secreting
molecules into neuron.
Progenitors of oligodentrocytes
 Raplidly proliferate during oligodentrocyte turnover.
Can potentially receive synapses.
Constantly sample their environment by sending out
processes.