Neurons and Glia
Neurons and Glia NSCI 3310
Popular in Cellular Neuroscience
Popular in Neuroscience
verified elite notetaker
This 7 page Class Notes was uploaded by Emma Notetaker on Tuesday September 29, 2015. The Class Notes belongs to NSCI 3310 at Tulane University taught by Jeffrey Tasker in Summer 2015. Since its upload, it has received 45 views. For similar materials see Cellular Neuroscience in Neuroscience at Tulane University.
Reviews for Neurons and Glia
Report this Material
What is Karma?
Karma is the currency of StudySoup.
Date Created: 09/29/15
Neurons and Glia 08/26/2015 100 billion neurons, 1-5 trillion glial cells neurons can receive up to thousand of synpases each second cells of the nervous system neurons: signaling cells o transfer of info o networks o pyramidal cells: triangle shaped; coordinates info within and sends out most of them have spines o stellate cells: starlike (dendrites in all directions) dendritic spines very important for signal transmission glial cells: support cells (support neural transmission through neuronal circuits) o maintain environment for neurons o connect neural circuits – talk to neurons via neurotransmitters and gliotransmitters o allow neurons to signals o receive signals from and transmit signals to neurons neuron morphological compartments: 1. Dendrites: o apical (off of apex)/basal (come off base of triangle) o dendritic spines: site of excitatory (mainly) synapse several different types; integrate inputs and changes inputs from other neurons (influences postsynaptic cell) o aspiny neurons both excitatory and inhibitory on dendritic shaft o primary fx: receive synapses 2. Soma (cell body, perikaryon): o nucleus: genetic material, RNA o can also receive synaptic input (usually inhibitory) o protein synthesis, packaging o neuritis: dendrites or axons (processes off soma) 3. Axon: o SINGLE axon o usually thinner than dendrites, ALWAYS aspiny o extends from soma via axon hillock or axon initial segment in this region, the chemical makeup is changing o multiple branches (axon collaterals) – all from single stem o axonal projections: Intrinsic: local projections in one area (usually interneurons and inhibitory) Extrinsic: project outside local area 4. Axon Terminal: synapse location (presynaptic) all cells in a network are both presynaptic AND postsynaptic Ramon y Cajal’s pyramidal neuron: picture: a=axon, b-d=basal dedrites invented Neuron Doctorine Information Flow - Neuron Doctorine: a neuron is a unit in a multi-unit circuit neuron polarity: o directionality of flow of info (dendrites soma axon terminal) o not symmetrical o presynaptic vs. postsynaptic (upstream vs. downstream) – relative to given synapse o orthograde direction of information flow dendrites: o excitatory and inhibitory o PASSIVE signal conductance: GRADED – directly proportional to input DECREMENTAL – smaller as it travels introduced charge attracts opposite charges – influences charges in a domino-like manner (passively transmitted from point A to point B) axon: o if enough charge reaches initial segment to reach threshold action potential! o action potential – changed from passive to ACTIVE conductance ALL OR NONE – goes all the way to maximum NONDECREMENTAL – regenerative (regenerated at every successive segment of axon) membrane opens channels axon terminal: synaptic transmission to postsynaptic cell o changes from electrical to chemical signal (neurotransmitter) electrical signal arrives at axon terminal and releases chemical signal, which opens electrical signals in postsynaptic cell o generates PASSIVE signal in postsynaptic cell (onto dendrites) backpropagation: exception to the rule o active signal conductance in dendrites o retrograde transmission via dendritic transmitters retrograde messengers: can have either positive or negative influences on synapses (facilitate or inhibit nt release) o influences forward direction of information flow o postsynaptic cell can release chemicals to presynaptic cell to influence signal coming back to itself modulates probability of nt release at that synapse Neuronal Morpholigies: 1. unipolar 2. bipolar: limited input, small surface area 3. pseudounipolar: sensory neurons 4. multipolar: multiple dendrites/inputs o high surface area o purkinje cells glia: Greek for glue – hold neurons together 1. microglia: from macrophages, phagocytic role o debridement, scar formation 2. macroglia: 4 types o 1. radial glia: path for migrating neurons more like the glue, sets up pathway and structure present in development o 2. myelin formation in CNS – insulation, increases conductance velocity ONE oligodendrocyte covers SEVERAL axons (white matter) o 3. Scwann cells: myelination in PNS – insulation, increase conductance neuronal regeneration (growth factors ONE covers ONE cell o 4. astrocytes: star glia buffer extracellular ions – always want electrical properties of ECF to be the same elimination of ions, elimination/recycling of transmitters (transport) involved in crosstalk between neurons Neurotransmitter clearance: astrocytes : o take up nt from extracellular space o uptake ions from ec space (change membrane potential) o diffusion barrier gliotransmission: like neurotransmitter released by glia signals to postsynaptic neuron to relay message back through synapse – retrograde signal goes back through astrocyte astrocyte responds with Ca influx which activates gliotransmitter at presynaptic neuron common gliotransmitter: ATP – can modulate presynaptic neuron **look at slide 13 functional components of neurons input component (dendrites/soma) o receptors on dendrites/synaptic potential negative resting potential depolarization via influx of Na o passive – graded, decremental (modulates signal importance) signal starting way out on dendrite will be weaker when it reaches cell body o mechanical/chemical - electric integrative (axon hillock/initial segment) o generating action potential active signal – all or none coded in number (length) and frequency (how often) o threshold – trigger level conductile component (axon) o action potential conducted to axon terminal – all or none output component (axon terminal) o nt release o action potential number and frequency converted to QUANTITY of neurotransmitters longer length or frequency will release more neurotransmitters energy transformation of signals: transduction: mechanical (stretch of receptor) passive electrical active electrical chemical mechanical knee jerk reflex: monosynaptic circuit monosynaptic circuit: o reflex excitation (in spinal cord) o extensor contraction disynaptic circuit: o reflex inhibition (inhibits nt release on opposing muscle to relax flexor – allows leg to kick out) o flexor relaxation ascending circuit: o polysynaptic o cognition universal model of neuronal function: nearly all neurons have the same functional organization (even though many morphologies and function) sensory motor neuroendocrine (release hormones at the end into blood – synapse onto capillary) interneuron (inhibitory) projection interneuron --?? excitatory, inhibitory **check slide 18