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lecture 7- excitatory neurotransmission
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lecture 7- excitatory neurotransmission

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@EnthusiasticChrysoprase4588

Questions and Answers

Which type of receptor is primarily responsible for fast excitatory synaptic transmission in the central nervous system?

  • Metabotropic receptors
  • NMDA receptors
  • AMPARs (correct)
  • Kainate receptors

    • What is required for NMDA receptor activation?

  • Only the influx of sodium
  • Only glutamate
  • Glutamate, glycine, and depolarisation (correct)
  • Glycine and a high concentration of calcium

    • What role does calcium flux through NMDA receptors play in the neuron?

  • It initiates apoptosis in neurons.
  • It promotes synaptic plasticity linked to learning and memory. (correct)
  • It reduces synaptic transmission.
  • It inhibits the activation of AMPARs.

    • What is the primary feature of NMDA receptor kinetics compared to AMPA receptors?

    <p>NMDA receptors have slow activation and deactivation kinetics.</p> Signup and view all the answers

    What is the relationship between synaptic activity and AMPAR regulation?

    <p>AMPAR activity can be regulated by second messenger cascades.</p> Signup and view all the answers

    What is the primary component of the late phase of excitatory postsynaptic currents (EPSCs)?

    <p>NMDA receptor activation</p> Signup and view all the answers

    In terms of location, where can NMDA receptors be found?

    <p>Both synaptic and extrasynaptic sites</p> Signup and view all the answers

    What is a key physiological role of dendritic spines on neurons?

    <p>They serve as sites for synaptic input reception.</p> Signup and view all the answers

    What is the primary consequence of CaMKaII activation during LTP?

    <p>It causes conformational changes in AMPARs to enhance sodium influx.</p> Signup and view all the answers

    Which of the following is necessary for the induction of LTP at CA3-CA1 synapses?

    <p>Postsynaptic calcium influx through NMDARs.</p> Signup and view all the answers

    Which receptor's activation is essential for Ca2+-mediated effects in LTP?

    <p>NMDA receptors.</p> Signup and view all the answers

    What is the end result of LTP in synaptic function?

    <p>Formation of new synaptic connections.</p> Signup and view all the answers

    What role does CaMKaII's self-phosphorylation play in LTP?

    <p>It prolongs the duration of LTP.</p> Signup and view all the answers

    What mechanism underlies long-term depression (LTD) in synaptic plasticity?

    <p>AMPARs removal from the postsynaptic membrane.</p> Signup and view all the answers

    Which process is enhanced as a result of LTP at the synapse?

    <p>Increased AMPAR insertion.</p> Signup and view all the answers

    What is the significance of the neurochemical cascade in the induction of LTP?

    <p>It triggers delivery and insertion of AMPARs.</p> Signup and view all the answers

    What is the primary function of AMPARs in the context of synaptic transmission?

    <p>They mediate fast synaptic transmission.</p> Signup and view all the answers

    Which of the following correctly describes the activation of Group I mGluRs?

    <p>They activate PLC which leads to the cleavage of PIP2.</p> Signup and view all the answers

    What role does calcium play in synaptic plasticity?

    <p>It is implicated in both synaptic strengthening and weakening.</p> Signup and view all the answers

    Which receptor has a slower opening and closing time compared to AMPARs?

    <p>NMDARs</p> Signup and view all the answers

    What potential outcome is expected from the binding of glutamate to Group I mGluRs?

    <p>Release of calcium from intracellular stores.</p> Signup and view all the answers

    What is the relationship between NMDARs and AMPARs in terms of their synaptic roles?

    <p>AMPARs are more sensitive to glutamate than NMDARs.</p> Signup and view all the answers

    How many distinct functional groups are there among the subtypes of Group I mGluRs?

    <p>3</p> Signup and view all the answers

    What happens when PIP2 is cleaved by PLC in the context of Group I mGluR activation?

    <p>It produces inositol-1,4,5-triphosphate, resulting in calcium release.</p> Signup and view all the answers

    What is the primary mechanism underlying changes in synaptic strength?

    <p>Long-term potentiation (LTP)</p> Signup and view all the answers

    Which region of the brain is crucial for memory and learning due to its role in long-term potentiation?

    <p>Hippocampus</p> Signup and view all the answers

    Which type of receptors are directly involved in initiating long-term potentiation in the hippocampus?

    <p>NMDA receptors</p> Signup and view all the answers

    What occurs prior to NMDA receptor activation during synaptic transmission?

    <p>Glutamate activates AMPA receptors.</p> Signup and view all the answers

    What is the consequence of long-term depression (LTD) on synaptic connections?

    <p>Decreases synaptic strength.</p> Signup and view all the answers

    How can synaptic plasticity be measured in the hippocampus?

    <p>By recording synaptic responses in hippocampal circuits.</p> Signup and view all the answers

    Which of the following describes a feature of AMPA receptors in the context of synaptic activity?

    <p>They play a role in early synaptic transmission.</p> Signup and view all the answers

    What best describes synaptic plasticity's role in neuronal circuits?

    <p>It underlies learning through structural changes.</p> Signup and view all the answers

    How does the activation time of mGluRs compare to that of iGluRs?

    <p>mGluRs activate much slower and last longer</p> Signup and view all the answers

    What is the primary role of mGluRs in neuronal activity?

    <p>To modulate synaptic activity by affecting channels and messenger systems</p> Signup and view all the answers

    According to Hebbian theory, what is a key characteristic of a Hebbian synapse?

    <p>It acts as a coincidence detector to strengthen the synapse</p> Signup and view all the answers

    What does long-term potentiation (LTP) primarily facilitate in the brain?

    <p>Increase in synaptic strength linked to recent activity</p> Signup and view all the answers

    Which components are associated with functions exhibiting Hebbian behavior?

    <p>NMDA receptors, action potentials, and EPSP summation</p> Signup and view all the answers

    Which statement about NMDA and AMPA receptors is correct?

    <p>Both NMDA and AMPA receptors are involved in synaptic plasticity</p> Signup and view all the answers

    What best describes the impact of neural plasticity on behavior?

    <p>It allows for adaptive changes in neural circuits influencing behavior</p> Signup and view all the answers

    Which process is associated with the growth of new neurons in response to experience?

    <p>Neurogenesis</p> Signup and view all the answers

    Study Notes

    Dendritic Spines

    • Dendrites of excitatory neurons are often adorned with spines that receive synaptic inputs from presynaptic axons.
    • Spines exhibit dynamic plasticity, enabling them to change in response to various stimuli.

    Glutamate Receptors

    • Ionotropic receptors (iGluRs) facilitate fast synaptic transmission with millisecond responses, allowing ions to flow in and out of neurons.
    • Metabotropic receptors (mGluRs) mediate slower synaptic transmission and activate messenger cascades, with responses taking seconds.

    Ionotropic Glutamate Receptors (iGluRs)

    • Primarily include AMPA receptors (AMPARs), NMDA receptors (NMDARs), and Kainate receptors.
    • AMPARs and NMDARs are often co-localized at glutamatergic synapses, mediating rapid chemical synaptic transmission, while also being present extrasynaptically and in autoreceptor roles.

    AMPA Receptors (AMPARs)

    • Open and close quickly, responsible for most fast excitatory transmission in the CNS.
    • They enable the influx of sodium (Na+), potassium (K+), and some calcium (Ca2+).
    • Structure consists of four subunits, GluA1, GluA2, GluA3, and GluA4, regulated by second messenger cascades involving various kinases.

    NMDA Receptors (NMDARs)

    • Named after the specific agonist NMDA, NMDARs are tetramers with a choice of three subunits.
    • Characterized by slow activation and deactivation kinetics, they require glutamate and glycine to activate.
    • Allow entry of calcium, sodium, and potassium, functioning as ligand and voltage-sensitive receptors.

    Coincidence Detectors

    • NMDARs necessitate glutamate, glycine, and a depolarized membrane potential to activate.
    • Play a critical role in synaptic plasticity, particularly important for learning and memory due to calcium flux.

    Kinetics of NMDA & AMPA Receptors

    • Non-NMDA receptors generate an early and large synaptic potential, while NMDA receptors contribute to a late component of excitatory postsynaptic currents (EPSCs).
    • AMPARs activate rapidly, whereas NMDARs respond slowly, allowing for unique timing in synaptic transmission.

    Long-Term Potentiation (LTP) and Depression (LTD)

    • LTP involves AMPAR insertion into the postsynaptic membrane, enhancing synaptic strength.
    • LTD involves the removal of AMPARs and is associated with the shrinkage of dendritic spines.
    • Both processes are thought to underlie mechanisms of learning and memory.

    Metabotropic Glutamate Receptors (mGluRs)

    • Comprised of single polypeptide chains with seven transmembrane domains, mGluRs engage in G-protein-mediated signaling cascades.
    • Activation pathways include the cleavage of PIP2 leading to the release of calcium from internal stores.

    Significance of mGluRs

    • mGluR activation results in slower, longer-lasting effects compared to iGluRs.
    • Effects are pervasive throughout neurons, modulating synaptic activity by changing presynaptic channel openings.

    Hebbian Synapses

    • Governed by the principle that "neurons that fire together, wire together," contributing to memory storage through synaptic strength enhancement.
    • NMDARs act as coincidence detectors, crucial for Hebbian learning mechanisms.

    Synaptic Plasticity and Changes

    • The nervous system exhibits plasticity, allowing for structural changes during learning, including the efficiency of synapses.
    • Mechanisms such as LTP and LTD are prevalent in the brain, with various forms identified across distinct synapses.

    Role of the Hippocampus

    • The hippocampus is critically involved in memory and learning, demonstrating LTP at multiple sites, particularly between CA3 and CA1 regions.
    • NMDA-dependent LTP within the hippocampus illustrates the importance of calcium influx and increased synaptic efficacy during stimulation.

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    Description

    This quiz covers the structure and function of dendritic spines on excitatory neurons, along with an exploration of glutamate receptors. It emphasizes the dynamic and plastic nature of these spines and the role of ionotropic receptors in fast synaptic transmission. Test your knowledge on these critical aspects of neuronal communication!

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