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Nolte – Chapter 1 (Introduction to the Nervous System) and all Class-Notes tagged with Chapter 1. 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. 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 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. 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 o NG2 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.