Neuron to Neuron Communication
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Questions and Answers

What is the primary purpose of voltage gated ion channels in synaptic transmission?

  • To generate an action potential in the postsynaptic neuron
  • To regulate the influx of calcium ions (correct)
  • To activate the mobilization of synaptic vesicles
  • To inhibit the release of neurotransmitters

    • What type of receptors are activated by GABA, resulting in an inhibitory postsynaptic potential?

  • Metabotropic GABA receptors
  • Ionotropic GABA receptors (correct)
  • Ionotropic glutamate receptors
  • Metabotropic glutamate receptors

    • What is the primary function of synaptic vesicles in synaptic transmission?

  • To inhibit the release of neurotransmitters
  • To generate an action potential in the presynaptic neuron
  • To store and release neurotransmitters (correct)
  • To regulate the activity of ion channels

    • What is the primary mechanism by which ionotropic receptors regulate the flow of ions across the membrane?

    <p>Allosteric binding, leading to a conformational change</p> Signup and view all the answers

    What type of potential is generated when glutamate binds to ionotropic glutamate receptors?

    <p>Excitatory postsynaptic potential (EPSP)</p> Signup and view all the answers

    What is the primary function of calcium ions in synaptic transmission?

    <p>To mobilize and fuse synaptic vesicles with the cell membrane</p> Signup and view all the answers

    Which of the following receptors has a single polypeptide subunit with 7 transmembrane alpha helices?

    <p>Muscarinic Acetylcholine Receptors</p> Signup and view all the answers

    What is the primary function of mGluRs of group II and III in the hippocampus?

    <p>Inhibiting transmitter release</p> Signup and view all the answers

    What is required as a co-transmitter for the activation of uncharacterized presynaptic mGluR?

    <p>Arachidonic acid</p> Signup and view all the answers

    Which of the following is NOT a characteristic of GABAB1?

    <p>Coupled to G-protein</p> Signup and view all the answers

    What is the effect of GABABR activation on Ca2+ channels?

    <p>Inhibiting Ca2+ channels</p> Signup and view all the answers

    What is the primary location of mGluRs of group I in the hippocampus?

    <p>Postsynaptic side</p> Signup and view all the answers

    What type of ions do NMDA receptors require for activation?

    <p>Sodium, potassium, and calcium ions</p> Signup and view all the answers

    What is the function of Mg2+ in NMDA receptors?

    <p>To block the receptor</p> Signup and view all the answers

    What is the significance of the post-synaptic calcium permeability of NMDA receptors?

    <p>It is important for synaptic plasticity and long-term potentiation</p> Signup and view all the answers

    What is the difference between AMPA and NMDA receptors?

    <p>NMDA receptors are blocked by Mg2+, while AMPA receptors are not</p> Signup and view all the answers

    What is the role of glycine in NMDA receptors?

    <p>It is a co-activator for NMDA receptors</p> Signup and view all the answers

    What is the structure of GABA(A) receptors?

    <p>Pentameric structure with 5 subunits</p> Signup and view all the answers

    What is the effect of propofol on GABA(A) receptors?

    <p>It increases the affinity of GABA for the receptor</p> Signup and view all the answers

    What is the difference between ionotropic and metabotropic receptors?

    <p>Metabotropic receptors are G-protein-coupled, while ionotropic receptors are not</p> Signup and view all the answers

    What is the function of G-proteins in metabotropic receptors?

    <p>To activate effector proteins</p> Signup and view all the answers

    What is the significance of long-term potentiation in synaptic plasticity?

    <p>It leads to synaptic potentiation</p> Signup and view all the answers

    Study Notes

    Neuron to Neuron Communication

    • Action potential reaches the synaptic terminal, leading to local voltage changes across the membrane
    • Voltage changes activate voltage-gated ion channels, resulting in an influx of calcium ions
    • Calcium ions trigger the mobilization and fusion of synaptic vesicles with the cell membrane, releasing neurotransmitters into the synaptic cleft

    Excitatory and Inhibitory Neurotransmission

    • Glutamate activates postsynaptic ionotropic glutamate receptors, causing an excitatory postsynaptic potential (EPSP)
    • GABA activates postsynaptic ionotropic GABA receptors, causing an inhibitory postsynaptic potential (IPSP)

    Ionotropic Receptors

    • Ionotropic receptors are ligand-gated ion channels, also known as neurotransmitter receptors
    • Neurotransmitter binding causes a conformational change, opening the ion channel
    • Examples: ionotropic glutamate receptors and ionotropic GABA receptors

    Metabotropic Receptors

    • Metabotropic receptors have one subunit with 7 transmembrane alpha helices (TM 1-7)
    • The cytoplasmic loops interact with G proteins
    • Examples: muscarinic acetylcholine receptors, adrenergic receptors, and metabotropic glutamate receptors

    Metabotropic Glutamate Receptors (mGluRs)

    • mGluRs of groups II and III are predominantly expressed on the presynaptic side, negatively linked to transmitter release
    • mGluRs of group I are found postsynaptically
    • Activation of presynaptic mGluRs increases transmitter release, requiring arachidonic acid as a co-transmitter

    Ionotropic Glutamate Receptors

    • Glutamate is the primary excitatory neurotransmitter in the mammalian brain
    • AMPA and NMDA-type glutamate receptors are the main receptors involved
    • NMDA receptors have a Mg2+ block, and their Ca2+ permeability is important for synaptic plasticity

    Ionotropic Glutamate Receptor Structure

    • Four transmembrane alpha helices (M1-M4)
    • The Glu binding domain is encoded on the N-terminal
    • The channel is formed by four subunits, surrounding the pore of the channel
    • When open, the ion channel is permeable to Na+, K+, and in some cases, Ca2+

    AMPA and NMDA Receptors

    • AMPA receptors: fast sodium entry, fast EPSP, fast inactivation
    • NMDA receptors: slow activation, Ca2+ permeability, stay open for a long time
    • NMDA receptors require co-activators: glycine and D-serine

    NMDA Receptor Kinetics

    • Glycine (together with glutamate) is required for the activation of NMDA receptors
    • NMDA receptors are readily blocked by magnesium (Mg2+)
    • Ketamine selectively blocks NMDA channels

    Molecular Integrators

    • NMDA receptors act as molecular integrators, opening only when the membrane is already depolarized by AMPA receptors
    • This allows Ca2+ to enter the cell, leading to synaptic plasticity, memory, long-term potentiation, and neuronal death

    GABA Receptors

    • GABA is the main inhibitory neurotransmitter in the vertebrate brain
    • GABA binds to GABAA receptors with high affinity
    • GABAA receptors have a pentameric structure with 5 subunits, an allosteric binding site for GABA, and a benzodiazepine binding site between alpha and gamma subunits

    GABA Functions

    • GABA(A) receptors contribute to several components of the anaesthetic state, including amnesia, sedation, hypnosis, and immobility
    • GABA(A) receptors are substrates for some general anaesthetics

    Propofol

    • Propofol is frequently used for the induction of anaesthesia
    • Propofol works by increasing GABA-mediated inhibition, decreasing the rate of dissociation of GABA from the GABAA receptor, leading to longer-lasting hyperpolarization of cell membranes

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    Description

    This quiz covers the process of synaptic transmission, including the action potential, ion channels, and neurotransmitter release. It also explores the role of excitatory neurotransmitters like glutamate. Test your knowledge of neuron communication!

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