Neuromuscular Junction Specializations
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Questions and Answers

Which of the following is a structural specialization at the neuromuscular junction that supports the localization of a high density of ACh receptors?

  • Formation of junctional folds (correct)
  • Presence of voltage-activated Ca2+ channels
  • Clustering of synaptic vesicles
  • Expression of voltage-activated sodium channels

    • What is the role of voltage-activated Ca2+ channels at the presynaptic terminal of the neuromuscular junction?

  • To release acetylcholine from synaptic vesicles
  • To increase the surface area of the postsynaptic membrane
  • To provide the calcium needed for vesicle exocytosis (correct)
  • To depolarize the postsynaptic muscle fiber

    • What is the electrical event generated in the postsynaptic muscle fiber following a presynaptic action potential that is caused by the influx of cations through ACh receptor channels?

  • Action potential
  • Activation of Na+ channels
  • Depolarization of the postsynaptic
  • End-plate potential (correct)

    • Which one of these is responsible for depolarizing the muscle fiber membrane potential to threshold for activation of voltage-gated Na+ channels?

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

    Why does a decrease in extracellular Ca2+ levels disrupt transmission at the neuromuscular junction?

    <p>It reduces the driving force for Ca2+ influx into the presynaptic terminal</p> Signup and view all the answers

    What are the main types of ligand-gated ion channels for glutamate?

    <p>AMPA, NMDA, and Kainate (KA) receptors</p> Signup and view all the answers

    What is the role of NMDA receptors in excitatory synaptic transmission?

    <p>They elicit increases in intracellular calcium</p> Signup and view all the answers

    What is the main function of the presynaptic terminal at the neuromuscular junction?

    <p>To release acetylcholine into the synaptic cleft</p> Signup and view all the answers

    What is the role of voltage-activated sodium channels at the postsynaptic muscle fiber?

    <p>To generate an action potential</p> Signup and view all the answers

    What is the function of the junctional folds in the postsynaptic muscle fiber?

    <p>To increase the surface area of the postsynaptic membrane</p> Signup and view all the answers

    What is the main function of voltage-activated Ca2+ channels at the presynaptic terminal?

    <p>To release acetylcholine into the synaptic cleft</p> Signup and view all the answers

    What is the significance of the density of ACh receptors at the crests of the junction folds?

    <p>It facilitates efficient activation of Na+ channels</p> Signup and view all the answers

    What is the role of synaptic vesicles at the presynaptic terminal?

    <p>To release acetylcholine into the synaptic cleft</p> Signup and view all the answers

    What is the main function of the end-plate potential (EPP) in the postsynaptic muscle fiber?

    <p>To generate an action potential</p> Signup and view all the answers

    What is the role of voltage-activated Ca2+ channels at the postsynaptic muscle fiber?

    <p>To generate an action potential</p> Signup and view all the answers

    What is the significance of the active zones at the presynaptic terminal?

    <p>They support the localization of synaptic vesicles</p> Signup and view all the answers

    What is the function of voltage-activated sodium channels at the presynaptic terminal?

    <p>To generate an action potential</p> Signup and view all the answers

    Temporal summation refers to

    <p>the process by which multiple EPSPs from a single presynaptic neuron add up over time to reach the threshold for an action potential in the postsynaptic neuron</p> Signup and view all the answers

    What is the role of synaptobrevin in synaptic vesicle fusion?

    <p>Synaptobrevin induces a conformational change in SNARE proteins to drive fusion of the vesicle membrane with the plasma membrane</p> Signup and view all the answers

    What happens when extracellular calcium levels are decreased at the neuromuscular junction?

    <p>The driving force for calcium influx during the presynaptic action potential is reduced</p> Signup and view all the answers

    Why do neurons in the central nervous system express different glutamate receptor subunits?

    <p>To produce different types of glutamate receptors with unique functional properties</p> Signup and view all the answers

    What are the main roles of AMPA receptors in excitatory synaptic transmission?

    <p>AMPA receptors produce postsynaptic depolarization at excitatory synapses</p> Signup and view all the answers

    What are the main roles of KA receptors in excitatory synaptic transmission?

    <p>KA receptors produce postsynaptic depolarization at excitatory synapses</p> Signup and view all the answers

    What are the main roles of NMDA receptors in excitatory synaptic transmission?

    <p>NMDA receptors produce postsynaptic depolarization at excitatory synapses</p> Signup and view all the answers

    What is the role of synaptotagmin in synaptic vesicle fusion?

    <p>Synaptotagmin induces a conformational change in SNARE proteins to drive fusion of the vesicle membrane with the plasma membrane</p> Signup and view all the answers

    What is the role of AMPA receptors in producing postsynaptic depolarization?

    <p>AMPA receptors have a high permeability to Ca2+ ions</p> Signup and view all the answers

    Why does a decrease in extracellular Ca2+ levels disrupt transmission at the neuromuscular junction?

    <p>It decreases the release of synaptic vesicles</p> Signup and view all the answers

    What are the proteins in the presynaptic terminal responsible for guiding synaptic vesicles to the plasma membrane and preparing them for eventual release?

    <p>SNARE proteins</p> Signup and view all the answers

    How does an action potential invading the presynaptic terminal of a motor neuron trigger synaptic vesicle fusion with the plasma membrane?

    <p>Through the interaction of Synaptotagmin and SNARE proteins</p> Signup and view all the answers

    Why do neurons in the central nervous system express so many different glutamate receptor subunits?

    <p>To create different types of glutamate receptors with unique functional properties</p> Signup and view all the answers

    What are the major types of ligand-gated ion channels for glutamate?

    <p>AMPA, NMDA, and Kainate (KA) receptors</p> Signup and view all the answers

    What are the main roles of AMPA, NMDA, and KA receptors in excitatory synaptic transmission?

    <p>AMPA receptors produce postsynaptic depolarization, KA receptors enhance transmitter release, and NMDA receptors regulate calcium-dependent signaling pathways</p> Signup and view all the answers

    What is temporal summation?

    <p>The process of adding up postsynaptic potentials generated by rapid synaptic inputs</p> Signup and view all the answers

    What is the role of Synaptotagmin in synaptic vesicle fusion with the plasma membrane?

    <p>It binds to the SNARE complex and induces a conformational change in the SNARE proteins</p> Signup and view all the answers

    What is the requirement for activation of NMDA receptors?

    <p>Both glutamate binding and strong depolarization of the postsynaptic cell</p> Signup and view all the answers

    What is the ion channel of AMPA receptors highly permeable to?

    <p>Na+ and K+ ions</p> Signup and view all the answers

    Which ion is excluded from entering the cell when GABAA receptors are activated?

    <p>Na+</p> Signup and view all the answers

    How many different types of GABAA receptors are there?

    <p>19</p> Signup and view all the answers

    Which GABAA receptor subtype generates an extra-synaptic pool of receptors?

    <p>Synaptic, γ subunit-containing receptors</p> Signup and view all the answers

    Which GABAA receptor subtype mediates phasic inhibitory transmission?

    <p>Extrasynaptic, δ subunit-containing receptors</p> Signup and view all the answers

    Which GABAA receptor subtype is persistently active and produces a persistent flux of Cl- into the cell?

    <p>Extrasynaptic, δ subunit-containing receptors</p> Signup and view all the answers

    What is the main effect of activation of GABAA receptors?

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

    What is the role of sedative-hypnotic drugs on GABAergic, inhibitory synaptic transmission?

    <p>Increase inhibitory transmission</p> Signup and view all the answers

    What is the role of anxiolytic drugs on GABAergic, inhibitory synaptic transmission?

    <p>Increase inhibitory transmission</p> Signup and view all the answers

    Which ion is responsible for the hyperpolarization produced by GABAA receptor activation?

    <p>Cl-</p> Signup and view all the answers

    What is the main role of GABAA receptors in inhibitory synaptic transmission?

    <p>Both mediating phasic inhibition and generating an extra-synaptic pool of receptors</p> Signup and view all the answers

    Which type of drugs primarily act by enhancing the affinity of GABAA receptors for GABA?

    <p>Benzodiazepine drugs</p> Signup and view all the answers

    What is the activity-dependent modulation of GABAergic inhibition mediated by endocannabinoids known as?

    <p>Depolarization-induced suppression of inhibition</p> Signup and view all the answers

    What is the category of conditions and/or injuries to the peripheral nerves called?

    <p>Peripheral neuropathy</p> Signup and view all the answers

    What is the term for damage to the axon and everything distal to the injury, including the axon and the myelin sheath?

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

    What is the term for damage to the cell body of a neuron?

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

    What is the term for damage to the myelin sheath of a nerve?

    <p>Segmental demyelination</p> Signup and view all the answers

    What is the better-understood form of retrograde synaptic transmission seen at some inhibitory synapses?

    <p>Depolarization-induced suppression of inhibition</p> Signup and view all the answers

    What is the name of the endogenous compounds similar to tetrahydrocannabinol (THC) found in cannabis?

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

    What activates enzymatic pathways that convert membrane lipids into endocannabinoids at inhibitory synapses?

    <p>Depolarization-induced suppression of inhibition</p> Signup and view all the answers

    What do endocannabinoids released from the postsynaptic cell do at inhibitory synapses?

    <p>Activate presynaptic cannabinoid receptors</p> Signup and view all the answers

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